ADDITIVE MANUFACTURING METHOD Field [0001] The present invention relates to the fields of synthesis of block copolymers, additive manufacturing, and micro- or nanostructured particles produced therefrom. However, it will be appreciated that the invention is not limited to these particular fields of use. Background [0002] The following discussion of the prior art is provided to place the invention in an appropriate technical context and enable the advantages of it to be more fully understood. It should be appreciated, however, that any discussion of the prior art throughout the specification should not be considered as an express or implied admission that such prior art is widely known or forms part of the common general knowledge in the field. [0003] Additive manufacturing and 3D printing technologies have greatly simplified the production of materials with arbitrary geometries and tailored chemical compositions. However, while 3D printing methods such as direct ink writing and stereolithography are capable of fabricating multi-materials with highly resolved micro- and macroscale features, these methods offer insufficient control over materials’ properties at the nanoscale and can be expensive. [0004] To achieve nano- and micro-scale material structuration in 3D printing, two main strategies have been previously explored. The first strategy relies on the development of precision hardware to decrease the voxel size in two-photon polymerization (2PP) processes. These systems have successfully produced polymeric materials with controlled structures on the sub-micrometre scale. However, these systems suffer from low production rates and the need for precisely engineered and expensive equipment. An alternative to hardware driven strategies are chemically controlled methods for nano- and micro-scale structuration. Systems which use this method typically rely on phase separation between thermodynamically incompatible components to drive the formation of discrete nano- and micro-scale domains throughout the 3D printed material. These chemical approaches are advantageous as they can produce nanostructured materials using inexpensive and highly accessible equipment with higher volume throughputs. [0005] Chemical control methods have been attempted previously using Direct Ink Writing (DIW) devices, however, the macroscopic material resolution is low due to inherent limitations in the DIW process. Other known methods involve using polymerization induced phase separation (PIPS) with photoinduced 3D printing to fabricate materials with microscale internal structures. While the use of photoinduced techniques provide more highly resolved geometrical structures, the employed phase separation processes in PIPS does not offer sufficient control over nanostructuration. [0006] One method of producing materials with controlled nanoscale features is through polymerization induced microphase separation (PIMS). However, PIMS generally requires controlled environments with high temperatures (above 100°C) and reaction times in the order of several hours. As a result, PIMS processes have not been successfully applied to 3D printing techniques. [0007] Accordingly, there is a need for an efficient, cost-effective method of 3D printing materials with nanoscale structuration, preferably using relatively simple devices and under mild conditions. Preferably, the process will be industrially achievable and commercially viable. [0008] It is an object of the present invention that at least one of the needs above is at least partially satisfied. [0009] It is an object of the present invention to overcome or ameliorate one or more of the disadvantages of the prior art, or at least to provide a useful alternative. Summary of Invention [00010] An additive manufacturing process for the manufacture of articles with microscale or nanoscale structuring has been disclosed herein. In particular, the inventors have advantageously developed a photo-PIMS resin that is suitable for use with simple, light-based additive manufacturing techniques for producing materials with structured domains. The resin has a fast curing time, which allows for the more rapid production of articles using an additive manufacturing process and allows the skilled person to tune the desired micro- or nano-scale structure by varying the relative ratios of reactants. The use of inexpensive manufacturing techniques to produce materials with a fine bulk structure are highly sought after and this invention represents a significant improvement over the prior art. [00011] Accordingly, in a first aspect of the present invention, there is provided an additive manufacturing method for producing an article with two co-continuous phases, the method comprising: (a) obtaining a resin comprising a macromolecular chain transfer agent, a noncrosslinking monomer, a crosslinking monomer and a photoinitiator, (b) loading the resin into a visible light-based additive manufacturing device; and (c) using the device to produce the article by exposing the resin to the light. [00012] The following options may be used in conjunction with the first aspect, either alone or in any suitable combination. [00013] The method of the first aspect utilises a macromolecular chain transfer agent. Accordingly, the first aspect may further comprise the step of forming the macromolecular chain transfer agent before step (a). The step of forming the acrylate-based macromolecular chain transfer agent may utilize RAFT polymerization and comprise the following steps: (1) combining a RAFT agent, a monomer or a polymer and a radical initiator or a coupling agent to form a reaction mixture; (2) heating the reaction mixture to a temperature of between about 40 and about 100°C for between 1 and 24 hours; (3) stopping the reaction by cooling below 0°C; and (4) purifying the obtained macromolecular chain transfer. [00014] Any suitable RAFT agent, monomer and radical initiator may be used. The skilled person may select any suitable reagents in order to obtain an efficient reaction and particular properties of the macromolecular chain transfer agent required. In a particular embodiment of the present invention, the macromolecular chain transfer agent is acrylate-based and is formed whereby the RAFT agent is 2-(Butylthiocarbonothioylthio)propanoic acid (BTPA), the monomer is n-butyl acrylate and the radical initiator is azobisisobutyronitrile (AIBN). In another embodiment, the macromolecular chain transfer agent is polysiloxane-based and is formed whereby the RAFT agent is BTPA, the polymer is polydimethylsiloxane (PDMS) and the radical initiator is AIBN. In another embodiment, the macromolecular chain transfer agent comprises two different polymer blocks in series and is formed by whereby the RAFT agent is BTPA, the monomer is n-butyl acrylate, the polymer is PDMS and the radical initiator is AIBN and the RAFT agent is exposed to the monomer first and then the polymer (or vice versa). [00015] The resin of the present invention comprises a macromolecular chain transfer agent. The macromolecular chain transfer agent comprises at least one polymer chain. It may comprise a polyacrylate (i.e., be an acrylate-based CTA), or it may comprise a polysiloxane (i.e., be a siloxane-based CTA), or it may comprise another suitable polymer. It may comprise two or more different polymer chains (i.e., be a co-block polymer-based CTA) whereby one chain is a polyacrylate chain and the other is a polysiloxane chain, for example. In one embodiment, the macromolecular chain transfer agent may consist of poly(n-butyl acrylate), referred to herein as PBA _n -CTA. In another embodiment, the macromolecular chain transfer agent may consist of PDMS, referred to herein as PDMS _n -CTA. In another embodiment, the macromolecular chain transfer agent may consist of a polyacrylate block consisting of poly(n-butyl acrylate) and a polysiloxane block consisting of PDMS, herein referred to as PDMS _n -b-PBA _n -CTA. Each n is any number, or any range, between 24 and 360. In preferred embodiments, the n for the PBA _n block is about 48 or about 80 and/or the n for the PDMS _n block is about 67. The macromolecular chain transfer agent of the present invention may be present at between about 16 wt% and about 45 wt% of the total weight resin. Particularly preferred amounts include 16.5 wt% PBA _n -CTA, 28.2 wt% PBA _n -CTA or 43.9 wt% PBA _n -CTA of the total weight of the resin. [00016] The resin of the present invention also comprises a non-crosslinking monomer and a crosslinking monomer. The monomers may be based on any suitable chemistry that is capable of chain extending the macromolecular chain transfer agent and also providing desired properties, such as a hydrophobicity that is relatively different compared to the macromolecular chain transfer agent (so as to illicit a phase separation during polymerisation) and has a high inherent Tg. In a preferred embodiment, the non-crosslinking monomer and the crosslinking monomer are both acrylate monomers. The non-crosslinking monomer may be any suitable monomer with a single vinyl group provided by an acrylate group (CH₂=CHC(=O)OR), a methacrylate group (CH₂=C(R)C(=O)OR), an acrylamide group (CH ₂ =CHC(=O)NRR’) or a methacrylamide (CH ₂ =C(CH ₃ )C(=O)NRR’) group. In a preferred embodiment, the non-crosslinking monomer may be acrylic acid. The crosslinking monomer may have two or more vinyl groups, whereby each vinyl bond may be provided by an acrylate group (CH₂=CHC(=O)OR), a methacrylate group (CH₂=C(R)C(=O)OR), an acrylamide group (CH ₂ =CHC(=O)NRR’) or a methacrylamide (CH ₂ =C(CH ₃ )C(=O)NRR’) group. The crosslinking monomer may be a diacrylate, a dimethacrylate, a diacrylamide, a dimethacrylamide, a triacrylate, a trimethacrylate, a triacrylamide, a trimethacrylamide, a tetraacrylate, a tetramethacrylate, a tetraacrylamide, a tetramethacrylamide, a pentaacrylate, a pentamethacrylate, a pentaacrylamide, or a pentamethacrylamide. It may be any suitable di-, tri-, tetra- or penta-acrylate or methacrylate. The crosslinking monomer may be polymeric, in that it is based on a polymer. In embodiments whereby the macromolecular chain transfer agent forms a relatively hydrophobic domain, the crosslinking monomer may be relatively hydrophilic, thereby driving the phase separation during curing, yet also providing the crosslinks required to arrest the phase separation. The crosslinking monomer may be based on a polyglycol. In some embodiments, the crosslinking monomer is poly(ethylene glycol) diacrylate (PEGDA). In a preferred embodiment, the PEGDA has a number-average molecular weight (M _n ) of about 250 g/mol. [00017] The resin of the present invention, in order to be photocurable, must also comprise a photoinitiator. Any suitable photoinitiator may be used. In a preferred embodiment, the photoinitiator is diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide (TPO). As the photoinitiator works in concert with the macromolecular chain transfer agent, it may be present at a molar ratio of photoinitiator to macromolecular chain transfer agent of from 0.1:1 to 0.3:1. [00018] The resin of the present invention may optionally further comprise an unreactive polymer. The polymer may be the same as the polymer used to form the macromolecular chain transfer agent or it may be different. Preferably, the unreactive polymer has the same properties as the chain transfer agent, such that the unreactive polymer acts to swell this domain during curing of the resin but does not participate in the curing of the resin. Accordingly, in a preferred embodiment, the unreactive polymer is PBA _n , whereby n is any number, or any range, between 24 and 360. When the unreactive PBA _n is present, it may be present at a molar ratio of PBA _n - CTA to PBA _n of between 0.5:0.5 and 1.0:0.1. [00019] The device used to produce the articles of the present invention may be any suitable, light-based additive manufacturing device. As the skilled person will appreciate, as the resin is photocurable, the additive manufacturing device must use light to cure each layer of the article to be produced. In a preferred embodiment, a relatively simple digital light processing (DLP) device may be used. The DLP device may be used according to convention. Use of the device may comprise the steps of : (a) applying a layer of resin, (b) exposing the layer of resin to visible light for between 60-240 seconds, and (c) repeating steps (a) and (b) until the article is formed. [00020] The articles produced by the method of the present invention have two co-continuous phases. The co-continuous phases may be microscale (i.e., between 1 μm and 1000 μm in at least one dimension) or they may be nanoscale (i.e., between about 1 nm and 1000 nm) in at least one dimension, or they may be a combination thereof (i.e., nanoscale in one dimension and microscale in another dimension). The co-continuous phases may be tuned in terms of size and distribution, which may have effects on the material in terms of flexibility, robustness and transparency. Tuning of the nano- or micro-scale structure of the material may be carried out by altering the relative amounts of the components of the resin. For instance, the weight ratio of crosslinking monomer to non-crosslinking monomer may affect the size and distribution of the domains, whereby too little crosslinking monomer may lead to large globular domains, whereas too much crosslinking monomer may lead to a fine dispersion of a domain. The weight ratio of crosslinking monomer to non-crosslinking monomer may also be selected based on the desired properties of the produced article, as crosslinking is associated with the Tg and rigidity of a cured polymer. In one preferred embodiment, the weight ratio of non-crosslinking monomer to crosslinking monomer is about 4:1. Likewise, the ratio of crosslinking monomer to macromolecular chain transfer agent may affect the domains of the produced article, due to the opposing properties of these components. In some embodiments, the molar ratio of crosslinking polymer to macromolecular chain transfer agent is from about 26:1 to about 240:1. It follows that, in preferred embodiment, the molar ratio of non-crosslinking polymer to macromolecular chain transfer agent is from about 6.5:1 to about 60:1. [00021] Accordingly, in a preferred embodiment of the present invention, the resin of the present invention may have molar ratios of non-crosslinking monomer to crosslinking monomer to macromolecular chain transfer agent to photoinitiator of about 120/30/1/0.3. [00022] The articles produced by the method of the present invention may be robust. By “robust”, it is meant that they have a relatively high tensile stress at break, which is a common parameter used in the art of material science and reflects that stress required to cause a failure in the material under test. Preferably, the article has a tensile stress at break of at least 15 MPa. [00023] In a second aspect of the present invention, there is provided an article produced by the additive manufacturing method of the first aspect. [00024] In a third aspect of the present invention, there is provided a polymer having at least two domains, comprising: a first domain comprising a polyacrylate and/or a polysiloxane, and a second domain comprising PEGDA. [00025] In a fourth aspect of the present invention, there is provided a use of the article of second aspect, or the co-continuous polymer of the third aspect, in a medical device, such as a microneedle drug delivery system. [00026] The reference to any prior art in this specification is not and should not be taken as an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge. Brief Description of Drawings [00027] Preferred features, embodiments and variations of the invention may be discerned from the following detailed description which provides sufficient information for those skilled in the art to perform the invention. The detailed description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way. The detailed description will make reference to a number of drawings as follows: [00028] Figure 1 shows an overview of a photo-RAFT PIMS process including typical PIMS reaction components for SPEs including a macroCTA (PBA-CTA), monomer (AA), and crosslinker (PEGDA), and an illustration of the PIMS self-assembly process. [00029] Figure 2 shows an ¹ H NMR spectrum (300 MHz, CDCl ₃ , 298 K) of PBA ₄₈ -CTA. * - residual BA monomer (1.9 wt%) and residual acetonitrile (MeCN, 1.1 wt%).1H NMR spectra of PBA ₂₄ -CTA and PBA ₉₄ -CTA have identical characteristic peaks. [00030] Figure 3 shows resins that were formulated using a fixed molar ratio of [AA]/[PEGDA] = 4:1 and a varied weight percentage of PBA-CTA as follows: (a) 16.5 wt%; (b) 28.2 wt%; (c) 43.9 wt%. X _n –PBA-CTA degree of polymerization. The kinetics experiments were performed in triplicate. Double bond conversions were determined using ATR-FTIR under 2.06 mW cm ^-2 violet light (λ _max = 405 nm). Some error bars fall within the size of the markers. [00031] Figure 4 shows polymerization kinetics for the resin formulations containing AA/PEGDA/PBA ₄₈ -CTA/TPO. (A) Effect of increasing TPO concentration. The molar ratio [AA]/[PEGDA]/[PBA ₄₈ -CTA]/[TPO] = 120/30/1/variable; (B) Kinetics plots for the resins with molar ratios of [AA]/[PEGDA]/[PBA ₄₈ -CTA]/[TPO] = 240/60/1/0.3 and [AA]/[PEGDA]/[PBA48-CTA]/[TPO] = 60/15/1/0.3. The kinetics experiments were performed in triplicate. Vinyl conversion at a time was determined using ATR-FTIR under 2.06 mW cm-2 violet light (λmax = 405 nm). [00032] Figure 5 shows Tan δ profiles for materials 3D printed at different rmacroCTA values. (A) Tan δ profiles over the range of -70 to 150°C for materials 3D printed using resins with different r _macroCTA ; (B) Tan δ profiles over the range of -60-0°C. r _macroCTA = w(PBA ₄₈ - CTA)/(w(PBA ₄₈ -CTA) + w(PBA ₄₈ )), where w(PBA ₄₈ -CTA) and w(PBA ₄₈ ) are wt. fractions of PBA ₄₈ -CTA and PBA ₄₈ in a resin, respectively. The total loading of PBA = 28.2 wt%. [00033] Figure 6 shows transmittance from 400-700 nm for the materials 3D printed with various r _macroCTA values, whereby the macroCTA is PBA-CTA (as set out in Table 8). [00034] Figure 7 shows the ¹ H NMR spectra (400 MHz, 298 K) of PDMS ₆₇ -CTA. [00035] Figure 8 shows ¹ H NMR spectra (400 MHz, 298 K) of PDMS ₆₇ -b-PBA ₈₀ -CTA. Definitions [00036] The following definitions are provided to enable the skilled person to better understand the invention disclosed herein. These are intended to be general and are not intended to limit the scope of the invention to these terms or definitions alone. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one having ordinary skill in the art to which the invention pertains. [00037] As used herein, the term “relatively”, or variations thereof, means a feature that is “in comparison” or “in relation” to some other feature. In other words, the term “relatively” indicates that the feature is not absolute but is rather compared to some other feature. By way of example, if a material is described as “relatively hydrophilic”, it is not meant that the material is hydrophilic, but rather it is more hydrophilic than some other material. [00038] As used herein, the term “comprising” means “including”. Variations of the word “comprising”, such as “comprise” and “comprises”, have correspondingly varied meanings. As used herein, the terms “including” and “comprising” are non-exclusive. As used herein, the terms “including” and “comprising” do not imply that the specified integer(s) represent a major part of the whole. [00039] The transitional phrase “consisting of” excludes any element, step, or ingredient not specified. If in the claim, such would close the claim to the inclusion of materials other than those recited except for impurities ordinarily associated therewith. When the phrase “consisting of” appears in a clause of the body of a claim, rather than immediately following the preamble, it limits only the element set forth in that clause; other elements are not excluded from the claim as a whole. [00040] The transitional phrase “consisting essentially of” is used to define a composition, process or method that includes materials, steps, features, components, or elements, in addition to those literally disclosed, provided that these additional materials, steps, features, components, or elements do not materially affect the basic and novel characteristic(s) of the claimed invention. The term “consisting essentially of” occupies a middle ground between “comprising” and “consisting of”. [00041] Where applicants have defined an invention or a portion thereof with an open-ended term such as “comprising”, it should be readily understood that (unless otherwise stated) the description should be interpreted to also describe such an invention using the terms “consisting essentially of” or “consisting of. ” In other words, with respect to the terms “comprising”, “consisting of”, and “consisting essentially of”, where one of these three terms are used herein, the presently disclosed and claimed subject matter may include the use of either of the other two terms. Thus, in some embodiments not otherwise explicitly recited, any instance of “comprising” may be replaced by “consisting of” or, alternatively, by “consisting essentially of”. [00042] Further, unless expressly stated to the contrary, “or” refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present). [00043] Also, the indefinite articles “a” and “an” preceding an element or component of the invention are intended to be non-restrictive regarding the number of instances (i.e., occurrences) of the element or component. Therefore “a” or “an” should be read to include one or at least one, and the singular word form of the element or component also includes the plural unless the number is obviously meant to be singular. [00044] Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients or reaction conditions used herein are to be understood as modified in all instances by the term “about”. The examples are not intended to limit the scope of the invention. In what follows, or where otherwise indicated, “%” will mean “weight %”, “ratio” will mean “weight ratio” and “parts” will mean “weight parts”. [00045] The terms “predominantly” and “substantially” as used herein shall mean comprising more than 50% by weight, unless otherwise indicated. [00046] As used herein, with reference to numbers in a range of numerals, the terms “about”, “approximately” and “substantially” are understood to refer to the range of -10% to +10% of the referenced number, preferably -5% to +5% of the referenced number, more preferably -1 % to + 1 % of the referenced number, most preferably -0.1 % to +0.1 % of the referenced number. Moreover, with reference to numerical ranges, these terms should be construed as providing support for a claim directed to any number or subset of numbers in that range. For example, a disclosure of from 1 to 10 should be construed as supporting a range of from 1 to 8, from 3 to 7, from 1 to 9, from 3.6 to 4.6, from 3.5 to 9.9, from 8 to 10, and so forth. [00047] As used herein, wt% refers to the weight of a particular component relative to total weight of the referenced composition. [00048] Complete disclosures of the patents, patent documents and publications cited herein are incorporated by reference in their entirety as if each were individually incorporated. Description of Embodiments [00049] The following description conveys exemplary embodiments of the present invention in sufficient detail to enable those of ordinary skill in the art to practice the present invention. Features or limitations of the various embodiments described do not necessarily limit other embodiments of the present invention or the present invention as a whole. Hence, the following detailed description does not limit the scope of the present invention, which is defined only by the claims. [00050] The present invention relates to a method of additively manufacturing an article, especially a nanostructured article. [00051] In particular, the inventors have developed a method for producing a nanostructured article using a visible light-based additive manufacturing device. As will be described in more detail below and with reference to the Examples, the method of the present invention has been developed to be an efficient process which utilises relatively low-cost additive manufacturing techniques based on the visible light curing of polymers. Advantageously, the method of the present invention uses a PIMS process to produce articles with a tuneable microstructure. PIMS Processes [00052] A typical PIMS system is composed of an homogenous system, containing a macroCTA, crosslinking monomer, non-crosslinking monomer and a radical initiator, which phase separates during polymerization to yield nanostructured materials. Without wishing to be bound by any theory, the inventors understand that the PIMS process relies on the in-situ chain extension of a macromolecular chain transfer agent (macroCTA) with monomers of opposing physical properties (generally solubility properties), in order to induce microphase separation between incompatible block segments. In particular, the macroCTA and polymer chain formed by the monomers have a positive Gibbs free energy of mixing (ΔG _mix ) upon polymerization. During polymerization, blocks of like properties thermodynamically aggregate together, but this microphase separation is simultaneously arrested via crosslinking to form distinct domains upon curing, thereby providing a material with micro- or nanoscale morphologies (see Figure 1). These domains may be discrete domains dispersed throughout a matrix, or they may be co- continuous and extend throughout the material. PIMS systems, including some photoinduced systems, allow a high degree of control over nanoscale morphologies and domain sizes. [00053] As the resin of the present invention is photocurable and uses a photoinitiator, the polymer of the method of the present invention may be referred to as a “photo-PIMS” system, which distinguishes it from the “thermal-PIMS” systems which are known in the art that utilise a thermal initiator. [00054] Advantageously, the relative size, structure and flexibility of the co-continuous domains can be tuned by modifying the composition of the resin. Macro-Chain Transfer Agent [00055] The resin of the present invention includes a macro-chain transfer agent (macroCTA). As the skilled person will appreciate, chain transfer agents are known in the art of polymerisation for controlling the average molecular weight of the produced polymer. Generally, a chain transfer agent is selected having regard to the polymer to be produced and the type of monomers to be polymerised. In the present invention, a macroCTA is prepared for use in the photocurable resin. By “macro-chain transfer agent” it is meant that the chain transfer agent is not a small molecule (i.e., less than 150 Da), but is rather a larger chain transfer agent (i.e., greater than 150 Da) that comprises more than one monomer. In one embodiment, the macroCTA may be produced using, and comprising, a reversible addition-fragmentation chain-transfer (RAFT) agent. RAFT polymerisation is a living polymerisation technique that is known to produce polymers with a narrow molecular weight distribution. The macroCTA of the present invention can be synthesized by reacting a RAFT agent, a polymer, a coupling agent and a nucleophilic catalyst in a solvent. [00056] The RAFT agent for use in the present invention may be a thiocarbonylthio agent, such as a trithiocarbonate agent, a dithioester agent, a thiocarbonate agent, or a xanthate agent. In one embodiment, the RAFT agent is a thiocarbonylthio agent. For example, it may be 2-(n- butylthiocarbonothioylthio) propanoic acid (BTPA) or 4-cyano-4- [(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid (CDTPA) or any other suitable RAFT agent. In one preferred embodiment, the RAFT agent is BTPA. [00057] The macroCTA of the present invention is formed by polymerising the RAFT agent with at least one monomer or a polymer. When used, the monomer used for forming the macroCTA (by polymerizing from the RAFT agent) may be any suitable monomer. It preferably is a non-crosslinking monomer (that is, only includes one reactive site). When used, the polymer added to the RAFT agent to form the macroCTA may be any suitable polymer. It is preferably a linear polymer. The monomer or the polymer may be selected based on properties such as logP, glass transition temperature or compatibility with another component of the resin. In other words, the polymer chemistry and average chain length of the macroCTA may be selected in conjunction with other components of the resin for a particular use or to achieve a particular structure in the cured polymer. In a preferred embodiment of the present invention, the monomer forms a hydrophobic block when incorporated into the polymer. Accordingly, the monomers may be based on acrylic acid, styrene, alkene, urethane, imide carbonate, siloxane or epoxide chemistry. The monomers may be further substituted to increase the relative hydrophobicity of these domains in the article material, for example they may be substituted with one or more fluorine, chlorine, bromine or iodine atoms, or alkyl groups (such as methyl, ethyl, propyl or butyl substituents) or aryl group (such as phenyl or benzyl groups), although the skilled person must also take into account the effects of such substituent groups on the stacking and/or steric interactions within the polymer. [00058] The inventors of the present invention have found that acrylic monomers are suitable for forming the macroCTA used herein. The acrylic monomer may be any monomer with a CH₂=CRCOOR’ moiety comprising only one carbon-carbon double bond that forms a hydrophobic polymer. As the skilled person would appreciate, acrylic monomers polymerize via a free radical addition reaction involving the carbon-carbon double bonds. The acrylic monomer may be acrylic or methacrylic. It may be, for example, a (meth)acrylic ester, a (meth)acrylamide, (meth)acrylic acid or some other non-crosslinking acrylic monomer (e.g. an alkoxymethacrylic ester). It may be, for example, ethyl acrylate, n-butyl acrylate, ethylene-methyl acrylate, methyl methacrylate, behenyl acrylate, iso-butyl acrylate, tert-butyl acrylate, isobornyl acrylate and 2- propylheptyl acrylate, or the like. In a preferred embodiment, the monomer is n-butyl acrylate (BA), which the inventors have found to be a particularly suitable monomer for inclusion in the macroCTA of the present invention. As the skilled person would appreciate, the ratio of monomer to RAFT agent can be adjusted to control the overall chain length of the macroCTA that is produced, whereby the ratio is approximately the number of monomer units added to the RAFT agent to produce the macroCTA. Accordingly, the molar ratio of monomer to RAFT agent may be between 10:1 and 400:1, whereby the monomer is in an excess compared to the RAFT agent. For example, the molar ratio of monomer to RAFT agent may be between about 10:1 and 50:1, or between about 25:1 and about 100:1, or between about 50:1 and about 250:1, or between about 200:1 and 500:1, such as about 10:1, 15:1, 19:1, 20:1, 21:1, 22:1, 23:1, 24:1, 25:1, 26:1, 27:1, 28:1, 29:1, 30:1, 31:1, 32:1, 33:1, 34:1, 35:1, 36:1, 37:1, 38:1, 39:1, 40:1, 41:1, 42:1, 43:1, 44:1, 45:1, 46:1, 47:1, 48:1, 49:1, 50:1, 51:1, 52:1, 53:1, 54:1, 55:1, 56:1, 57:1, 58:1, 59:1, 60:1, 70:1, 71:1, 72:1, 73:1, 74:1, 75:1, 76:1, 77:1, 77:1, 78:1, 79:1, 80:1, 81:1, 82:1, 83:1, 84:1,85:1, 86:1, 87:1, 88:1, 89:1, 90:1, 91:1, 92:1, 93:1, 94:1, 95:1, 96:1, 97:1, 98:1, 99:1, 104:1, 109:1, 114:1, 119:1, 124:1, 129:1, 134:1, 139:1, 144:1, 149:1, 154:1, 159:1, 164:1, 169:1, 174:1, 179:1, 184:1, 189:1, 194:1, 200:1, 210:1, 220:1, 230:1, 240:1, 250:1, 260:1, 270:1, 280:1, 290:1, 300:1, 310:1, 320:1, 330:1, 340:1,350:1, 355:1, 360:1, 365:1, 370:1, 380:1, 390:1 or 400:1, or any molar ratio in between. [00059] The inventors have also found that the addition of a polysiloxane to the RAFT agent to form the macroCTA is also suitable for producing a nano-or microstructured article of the present invention. The polysiloxane may be functionalised with one or more alkyl groups to render the polymer relatively hydrophobic. The polysiloxane may have the general formula R[Si(R ₂ )O] _n SiR ₃ , whereby n is the number of polymer repetitions and each R is selected from any suitable alkyl group (such as methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, sec-butyl, and the like). In one preferred embodiment, each R is methyl (that is, the polysiloxane is of general formula CH ₃ [Si(CH ₂ CH ₂ )O] _n Si(CH ₃ ) ₃ , also referred to herein as PDMS. The molar ratio of polymer to RAFT agent may be the same as that described above for the monomer. [00060] A radical initiator is used to facilitate the binding of the monomer to the RAFT agent. Without wishing to be bound by any theory, it is understood that the radical initiator is a chemical substance that can produce a radical species which, in turn, reacts with a monomer unit to create a propagating chain, which can then react with the RAFT agent to facilitate chain extension. The radical initiator may generate radicals through any appropriate means, for example, through thermal, chemical or photocatalytic means. The skilled person would be able to select an appropriate initiator depending on the chemistry involved in the producing any particular macroCTA. Non-limiting examples of radical initiators suitable for the invention include one or more of the following compounds: 2,2’-azobis(isobutyronitrile ), 2,2’-azobis(2- cyanobutane), dimethyl 2,2’azobis(isobutyrate), 4,4’-azobis(4-cyanovaleric acid), 4,4’-azobis-(4- cyanopentanoic acid), 2,2’-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, 1, 1 ‘- azobis(cyclohexanecarbonitrile), 2-(t-butylazo)-2-cyanopropane, 2,2’-azobis{2-methyl-N-[1,1- bis(hydroxymethyl)-2-hydroxyethyl]propionamide}, 2,2’-azobis[2-methyl-N-(2- hydroxyethyl)propionamide], 2,2’-azobis(N,N’dimethyleneisobutyramidine) dihydrochloride, 2,2’-azobis(2-amidinopropane) dihydrochloride, 2,2’-azobis(N,N’-dimethyleneisobutyramidine), 2,2’-azobis{2- methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide }, 2,2’- azobis{2- methyl-N-[ 1, 1-bis(hydroxymethyl)-2-ethyl]propionamide}, 2,2’-azobis[2-methylN- (2-hydroxyethyl)propionamide], 2,2’-azobis(isobutyramide) dihydrate, 2,2’azobis(2,2,4-9 trimethylpentane), 2,2’-azobis(2-methylpropane), t-butyl peroxyacetate, t-butyl peroxybenzoate, t-butyl peroxyneodecanoate, t-butylperoxy isobutyrate, t-amyl peroxypivalate, t-butyl peroxypivalate, diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, dicumyl peroxide, dibenzoyl peroxide, dilauroyl peroxide, potassium peroxydisulfate, ammonium peroxydisulfate, di-t-butyl hyponitrite, dicumyl hyponitrite, and the like. However, the inventors of the present invention have found 2,2’-azobisisobutyronitrile (AIBN) to be a particularly suitable thermal radical initiator for the present invention. The skilled person will appreciate that the radical initiator may be added in relatively small amounts compared to the monomer and/or the RAFT agent, as it is only required to initiate the polymerisation reaction. As the skilled person would appreciate, the amount of radical initiator required will be related to the amount of RAFT agent used (since the radical initiator and RAFT agent interact to initiate polymerisation), whereby the RAFT agent is usually in excess. Accordingly, the molar ratio of radical initiator to RAFT agent may be between about 0.1:1 and 1:1, or between about 0.1:1 and 0.2:1, or between about 0.5:1 and 1:1, such as about 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, or 1:1, or any range therein. [00061] When a pre-formed polymer is added to the RAFT agent, a radical initiator is not often used. Rather, a coupling agent is used to covalently bond the polymer to the RAFT agent. Without being bound to theory, it is understood that the coupling agent can be an ester group, amide group or other. Accordingly, any suitable coupling agent may be used. By way of a non- limiting example, the coupling agent may be N-(3-(dimethylamino)propyl)-N′-ethylcarbodiimide hydrochloride (EDC·HCl) although any suitable coupling agent may be used. [00062] The reaction to form a macroCTA of the present invention occurs in a solvent. Any suitable solvent which dissolves or at least disperses the RAFT agent, the monomer or polymer, and the radical initiator or coupling agent without participating in the coupling reaction, may be used. It is anticipated that the skilled person could select a suitable solvent to be used based on the chemistry of the reagents used. In one preferred embodiment, the inventors have found that acetonitrile is a suitable solvent. [00063] In one preferred embodiment, the macroCTA is formed by the reaction of BA, BTPA and AIBN, with acetonitrile as the solvent. The macroCTA formed from this reaction is designated herein as PBA _n -CTA, which refers to a chain transfer agent (CTA) comprising poly(n-butyl acrylate) of n monomers in length. As discussed above, the ratio of BA to BTPA can be adjusted to control the overall chain length of the PBA _n -CTA that is produced. Accordingly, the molar ratio of BA to BTPA (that is, the ratio of monomer to RAFT agent) may be between 10:1 and 400:1, whereby the monomer is in an excess compared to the RAFT agent. In a preferred embodiment, the ratio of BA to BTPA is between about 24:1 and about 94:1. In a particularly preferred embodiment, the ratio of BA to BTPA is about 48:1. Accordingly, a preferred macroCTA of the present invention is between PBA24-CTA and PBA ₉₆ -CTA, and more preferably is PBA ₄₈ -CTA. The molar ratio of BTPA to AIBN may be between about 2:1 and 10:1. In preferred embodiments, the molar ratio is between 5:1 and 8:1. It follows that, overall, the molar ratio of the reactants falls within the ratio ranges of BA:BTPA:AIBN of (10- 400):1:(0.1-0.2). In a preferred embodiment, the macroCTA is produced from a ratio of reactants BA:BTPA:AIBN of 48:1:0.14. [00064] In another preferred embodiment, the macroCTA is formed by the reaction of PDMS- OH, BTPA and EDC·HCl, with dichloromethane as the solvent. The macroCTA formed from this reaction is designated herein as PDMS _n -CTA, which refers to a chain transfer agent (CTA) comprising PDMS of n monomers in length. Any suitable length of PDMS can be used. Accordingly, the molar ratio of PDMS to BTPA (that is, the ratio of polymer to RAFT agent) may be between 10:1 and 400:1, whereby the polymer is in an excess compared to the RAFT agent. A preferred macroCTA of the present invention is between PBA ₄₀ -CTA and PBA ₉₆ -CTA, and more preferably is PBA ₆₇ -CTA. The molar ratio of BTPA to EDC·HCl may be between about 0.5:1 and 10:1. In preferred embodiments, the molar ratio is between 0.5:1 and 2:1 [00065] The macroCTA of the present invention can be formed using two steps to create a co- block polymer covalently bound to the RAFT agent. The two steps may be two polymerization steps, or two polymer coupling steps, or a polymerization step followed by a polymer coupling step, or a polymer coupling step followed by a polymerization step. In another preferred embodiment, the macroCTA comprises a PBA _n block as described herein and a PDMS _n block as described herein. As the skilled person would expect, such macroCTAs may be referred to as, for example, PDMS _n -b-PBA _n -CTA. The methods described herein can be easily adapted by the skilled person to form co-block polymers. [00066] The process for preparing the macroCTA of the present invention may include steps including: (1) combining the RAFT agent, monomer, radical initiator and solvent; or combining the RAFT agent, polymer, coupling agent and solvent, optionally with stirring and optionally with deoxygenation of the solution; (2) heating the mixture to an appropriate temperature with optional stirring; (3) stopping the reaction by cooling and exposing the reaction to air; (4) followed by drying of the macroCTA, optionally with one or more purification steps. It is envisioned that parameters such as the amounts of reagents, time of each step, temperature of reaction and specific purification steps would be within the routine optimisation of the skilled person, based on the common general knowledge in the art. In one non-limiting example, the method comprises the following general steps: (1) combining the monomer, RAFT agent, radical initiator and solvent in a suitable flask to form a mixture, at a ratio of about (10-400):1:(0.1-0.2) respectively; (2) heating the mixture to an appropriate temperature for between about 1 and 24 hours, such as between about 10 and 20 hours, or between about 12 and 17 hours, or about 15 hours, or less than 1 hour, for example about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50 or 55 minutes; (3) stopping the reaction by cooling the solution to a temperature between about 0°C and -40°C or between about -10°C and -30°C such as about 0°C, -1°C, -2°C, -3°C, -4°C, - 5°C, -6°C, -7°C, -8°C, -9°C, -10°C, -11°C, -12°C, -13°C, -14°C, -15°C, -16°C, -17°C, - 18°C, -19°C, -20°C, -21°C, -22°C, -23°C, -24°C, -25°C, -26°C, -27°C, -28°C, -29°C, - 30°C, -31°C, -32°C, -33°C, -34°C, -35°C, -36°C, -37°C, -38°C, -39°C or -40°C; and (4) the solution is then concentrated by any appropriate means, such as rotary evaporation, optionally with one or more purification steps (e.g. filtration to remove by- products), and any further suitable steps, such as resolubilisation in an alternative solvent, acidification, further filtration steps, centrifugation, and desiccation, to obtain a dry macroCTA. The macroCTA prepared may be subjected to analysis by characterisation techniques, such as ¹ H NMR and size exclusion chromatography (SEC) to confirm the macroCTA that is produced by this method. [00067] The skilled person will appreciate that the appropriate temperature in step (2) may vary due to a number of factors, such as the particular combination of monomer, RAFT agent, radical initiator and solvent used, or the ratios thereof. For example, the temperature may be between about 20°C and 100°C or between about 40°C and 80°C such as 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C. In a preferred embodiment, step (2) includes heating the reaction to about 60°C. [00068] As the skilled person would appreciate, the method of forming the macroCTA agent may be optimisable, depending on the specific reagents used and the purification of the macroCTA agent that is desired. A non-limiting example of this method is provided in the Examples section below for illustration purposes. [00069] It will be appreciated that the average-number molecular weight of the macroCTA produced in this way is determined by the molar ratio of BA to RAFT agent. In some embodiments, the macroCTA has a number-average molecular weight (M _n ) (measured by ¹ H NMR spectroscopy), of between about 3 and 50 kg/mol or between about 3 and 47 kg/mol, or between about 3 and 7 kg/mol, or between about 6 and 13 kg/mol, or between about 12 and 24 kg/mol, or between about 23 and 47 kg/mol, for example about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49 or 50, or any number in between. In one preferred embodiment, the macroCTA has a M _n of about 3.3 kg/mol. In another preferred embodiment, the macroCTA has a M _n of about 6.4 kg/mol. In one preferred embodiment, the macroCTA has a M _n of about 12.3 kg/mol. In one preferred embodiment, the macroCTA has a M _n of about 23.3 kg/mol. In one preferred embodiment, the macroCTA has a M _n of about 46.4 kg/mol. Resin [00070] The resin of the present invention comprises a macroCTA as described above, a non- crosslinking monomer, a crosslinking monomer, and a photoinitator. As will be explained in more detail below, the chemical properties of each of the reactants can be selected so that when the resin is exposed to visible light (thereby exciting the photoinitiator and initiating polymerisation), the macroCTA undergoes chain extension with a polymer chain formed from the monomers extending from the reactive site of the macroCTA, such that the combination of polymer chain and macroCTA has a positive ΔG _mix parameter. In one particular arrangement, the macroCTA is PBA _n -CTA (which is relatively hydrophobic compared to the other reactants) and the polymer chain is relatively hydrophilic compared to the macroCTA. This contrast in physical properties leads to the material self-assembling during polymerisation to maximise thermodynamically favourable interactions between blocks with similar properties. However, simultaneous crosslinking between polymer blocks acts to kinetically arrest this emergent self- assembly structure, resulting in a morphology with two distinct microscale or nanoscale domains corresponding to the hydrophilic crosslinked polymer network and the hydrophobic macroCTA blocks. By adjusting the relative molecular weight of the macroCTA, a range of morphologies can be achieved, such as non-phase separated materials, discrete spherical or elongated domains, and phase separated bi-continuous domains. [00071] The resin of the present invention comprises the macroCTA described above. In preferred embodiments of the present invention, the monomer used in forming the macroCTA is BA as defined above. Accordingly, it is preferred that the macroCTA is a poly-BA (PBA)-based CTA (herein referred to as PBA _n -CTA). Without wishing to be bound by any theory, the inventors understand that PBA _n is a particularly suitable polymer for inclusion in the macroCTA of the present invention. In some embodiments, the resin of the present invention comprises or contains PBA _n -CTA at between about 5 wt% and about 63 wt% of the total mass of the resin, for example between about 10 and 20 wt%, or between about 25 and 35 wt%, or between about 40 and 50 wt%, or less than 63 wt% such as 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62 or 63 wt%, or any range in between of the total mass of the resin. macroCTA. In preferred embodiments, the resin comprises 16.5 wt% PBA _n -CTA, 28.2 wt% PBA _n -CTA or 43.9 wt% PBA _n -CTA. [00072] The resin of the present invention also comprises a non-crosslinking monomer and a crosslinking monomer. As will be described below, monomers based on acrylic chemistry may be particularly suitable due to their faster propagation rates compared to other polymerisation systems, such as those based on styrenic monomers. The inventors consider that fast propagation rates will be especially suitable for use in the present invention, as it will allow for faster curing of each layer in the light-based additive manufacturing process and therefore advantageous overall build speeds to be achieved. It is also understood that acrylic polymers, and particularly acrylic polymers with at least some degree of crosslinking, are particularly suitable as they lead to polymers with a high glass transition (Tg) temperature. [00073] The non-crosslinking acrylic monomer for use in the resin of the present invention is any monomer comprising only one carbon-carbon double bond. For example, it may be of general formula CH₂=CRCOOR, or CH ₂ =CRC(=O)R, or CH ₂ =CH-CN). As the skilled person would appreciate, acrylic monomers (either crosslinking or non-crosslinking) polymerize via a free radical addition reaction involving the carbon-carbon double bonds. Therefore, if an acrylic monomer has one carbon-carbon double bond, it can only polymerise in a linear chain (hence the use of the phrase “non-crosslinking acrylic monomer”). The non-crosslinking monomer may be acrylic or methacrylic. It may be, for example, a (meth)acrylic ester, a (meth)acrylamide, (meth)acrylic acid or some other non-crosslinking acrylic monomer (e.g. an alkoxymethacrylic ester). It may be, for example, acrylic acid, ethyl acrylate, ethylene-methyl acrylate, n-butyl acrylate, methyl methacrylate, 2-chloroethyl vinyl ether, 2-hydroxyethyl acrylate, 4- hydroxyethyl acrylate, behenyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, iso- butyl acrylate, tert-butyl acrylate, isobornyl acrylate, and 2-propylheptyl acrylate, or the like or any combination thereof. In a preferred embodiment, the non-crosslinking acrylic monomer is acrylic acid (AA). In some embodiments of the present invention, the resin comprises or contains the non-crosslinking monomer at between about 20 wt% and about 55 wt% of the total mass of the resin, or between about 25 and 35 wt%, or between about 35 and 45 wt%, or between about 40 and 50 wt%, or between about 25 and 45 wt%, or between about 35 and 50 wt% such as about 20, 20.521, 21.522, 22.5, 23, 23.5, 24, 24.5, 25, 25.5, 26, 26.5, 27, 27.5, 28, 28.5, 29, 29.5, 30, 30.5, 31, 31.5, 32, 32.5, 33, 33.5, 34, 34.5, 35, 35.5, 36, 36.5, 37, 37.5, 38, 38.5, 39, 39.5, 40, 40.5, 41.5, 42, 42.5, 43, 43.5, 44, 44.5, 45, 45.5, 46, 46.5, 47, 47.5, 48, 48.5, 49, 49.5, 50, 50.5, 51, 51.5, 52, 52.5, 53, 53.5, 54, 54.5 or 55 wt%, or any range in between, of the total mass of the resin. [00074] The crosslinking acrylic monomer is also based on acrylic acid chemistry but comprises at least two carbon-carbon double bonds. Given the free radical addition reaction polymerization of acrylic monomers (discussed above), if an acrylic monomer has two (or more) carbon-carbon double bonds (as is the case with the crosslinking monomer required by the present invention), these monomers have two (or more) sites that may polymerize (i.e., react with another monomer). When incorporated into an acrylic polymer, such monomers introduce branching and crosslinks to other polyacrylate chains (hence the use of the phrase “crosslinking monomer”). Preferably, the crosslinking monomer selected for use in the resin of the present invention is thermodynamically incompatible with the macroCTA, such that the crosslinking monomer provides the thermodynamic drive required to form the distinct domains during polymerisation. The crosslinking monomer may be a (meth)acrylic ester or a (meth)acrylamide. In the case of an ester, it may be an ester of a diol, a triol, a tetraol, a pentaol or some other polyol, i.e. it may be a diester, triester, tetraester or pentaester etc. In the case of an amide, it may have the structure HN((=O)C-CH=CH ₂ ) ₂ , N((=O)C-CH=CH ₂ ) ₃ or some other similar structure. It may be a di- acrylate (such as 1,6-hexanediol diacrylate, for example), a tri-acrylate (such as trimethylolpropane triacrylate, for example) or a tetra-acrylate. The monomer may be di- acrylate, a tri-acrylate or a tetra-acrylate-containing polymer based on a hydrophilic moiety. The hydrophilic polymer moiety may be a polyglycol (such as poly(ethylene glycol), poly(propylene glycol) or the like), a polysaccharide (such as dextran, alginate, agarose or the like), a peptide or derivatives thereof. The monomer may be a hydroxy functional monomer (such as ethylene glycol dimethacrylate, poly(ethylene glycol) diacrylate or the like). The monomer may be further substituted in order to increase the hydrophilicity of the monomer, for example it may be substituted with hydroxyl, amine or carboxyl groups. In a preferred embodiment, the crosslinking monomer is poly(ethylene glycol) diacrylate (PEGDA). In some embodiments of the present invention, the resin comprises or contains the crosslinking acrylate monomer at between about 15 wt% and about 45 wt% of the total mass of the resin, or between about 20 and 30 wt%, or between about 28 and 38 wt%, or between about 33 and 43 wt%, or between about 20 and 38 wt%, between about 28 and 43 wt% such as about 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44 or 45 wt%, or any range in between, of the total mass of the resin. [00075] Preferably, the crosslinking acrylic monomer and the non-crosslinking acrylic monomer are selected based on their properties when polymerised to form a polymer chain, whereby the properties of the polymer chain are preferably in contrast to the macroCTA. For example, when the macroCTA is relatively hydrophobic (such as PBA _n -CTA or PDMS _n -CTA or combinations thereof), monomers that lead to a polymer chain that is relatively more hydrophilic are selected so as to illicit spontaneous phase separation during polymerisation. [00076] Another material property that may contrast between the macroCTA and the polymer chain is the glass transition temperature (Tg). As the skilled person would appreciate, the Tg is a common term used in the art of polymer chemistry to define the temperature at which the molecules of an amorphous polymer reversibly change their mobility, such that at temperatures above the Tg it behaves “rubbery” (or less rigid) and at temperatures below the Tg it behaves “glassy” (or more rigid). In one preferred embodiment, the macroCTA, due to an absence of crosslinking, may have a low Tg, and the polymer chain, due to the presence of crosslinking, may have a high Tg. By “low Tg”, it is meant that the polymer (if prepared alone), would have a Tg lower than room temperature, such as less than about 20°C, or less than about 10°C, or less than about 0°C, or less than about -10°C, for example between about 20°C and -20°C, or between about 10°C and -30°C, or between about 0°C and -30°C, or between about -10°C and - 40°C, or between about -20°C and -50°C, or about 20°C, 15°C, 10°C, 5°C, 0°C, -5°C, -10°C, - 15°C, -20°C, -25°C, -30°C, -35°C, -40°C, -45°C or -50°C. By “high Tg”, it is meant that the polymer (if prepared alone), would have a Tg of greater than room temperature, such as greater than about 30°C , or greater than about 40°C, or greater than about 50°C, or greater than about 60°C, or greater than about 70°C, or greater than about 75°C, or between about 40°C and 120°C, or between about 50°C and 150°C, or between about 60°C and 80°C, or between about 80°C and 100°C, such as about 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, or more, or any range therein. As the skilled person would appreciate, once cured, the domain comprising the macroCTA having a low Tg could be considered to be the “soft” domain, and the domain comprising the polymer chain having a high Tg could be considered to be the “hard” domain. In a preferred embodiment, the hard domains of the article remain at a temperature below their Tg during storage (i.e., at room or ambient temperature). Preferably, the hard domains of the article also remain at a temperature below their Tg during use of the article. [00077] The resin of the present invention also comprises a photoinitiator. As the skilled person will appreciate, the photoinitiator initiates the chain extension of the PBA _n -CTA and subsequent polymerisation of the acrylic system, incorporating both crosslinking and non-crosslinking monomers. Any suitable photoinitiator that is excited by visible light can be used in the resin of the present invention. By “visible light”, it is meant that the electromagnetic radiation used is with a wavelength between about 380nm and about 700nm. The photoinitiator may be a Norrish type-I photoinitiator or it may be a Norrish type-II photoinitiator. Preferably, the photoinitiator used in the resin of the present invention can efficiently initiate RAFT polymerisation under open-air conditions. It may be, for example, 2,2-dimethoxy-1,2-diphenylethan-1-one, 1- hydroxycyclohexylphenyl-ketone, 2-hydroxy-2-methyl-1-phenylpropanone, diphenyl(2,4,6- trimethylbenzoyl) phosphine oxide (TPO) or the like. In one preferred embodiment, the photoinitiator is diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide (TPO). The photoinitiator is excitable at a visible wavelength, for instance it may be excitable at a wavelength between 380 nm and 500 nm, or between 400 nm and 600 nm, or between 600 nm and 700 nm, or between 400nm and 500 nm, such as 380, 385, 390, 395, 400, 405, 410, 415, 420, 425, 430, 435, 440, 445, 450, 455, 460, 465, 470, 475, 480, 485, 490, 495, 500, 505, 510, 515, 520, 525, 530, 535, 540, 545, 550, 555, 560, 565, 570, 575, 580, 585, 590, 595, 600, 605, 610, 615, 620, 625, 630, 635, 640, 645, 650, 655, 660, 665, 670, 675, 680, 685, 690, 695 or 700 or any suitable range therein. In a preferred embodiment, a violet coloured light at about 405 nm may be used. The light source may be a tuneable light source capable of producing a narrow band of electromagnetic wavelengths, or it may be a white light source that produces a wide range of electromagnetic wavelengths. Advantageously, as the non-crosslinking monomer and the crosslinking monomer are based on the same chemistry, the same photoinitiator initiates polymerisation reactions with both monomers, leading to the extension of the macroCTA chain and simultaneous chain branching, which leads to the preferred microscale or nanoscale co- continuous domains. The photoinitiator of the present invention may be found in the resin at concentrations of between about 0.1 and about 5.0 wt% of the total mass of the resin, such as between about 0.1 and 0.5 wt%, or between about 0.3 and 0.7 wt%, or between about 0.5 and 2.5 wt%, or between about 1 and 4 wt%, or between about 0.3 and 4.5 wt% such as about 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9 or 5.0 wt%, or any range in between. In one preferred embodiment, the photoinitator is present at about 0.3 wt% of the total mass of the resin. In another preferred embodiment, the photoinitator is present at about 0.5 wt% of the total mass of the resin. In another preferred embodiment, the photoinitator is present at about 0.7 wt% of the total mass of the resin. Accordingly, the molar ratio of photoinitiator to macroCTA may be between about 0.1:1 and about 2.4:1, such as between about 0.1:1 and 0.3:1, or between about 0.2:1 and 1:1, or between about 0.5:1 and 2:1, or between about 1:1 and 2.4:1, or about 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1 or 2.4:1 or any range therein. [00078] The inventors have found the properties of the self-assembled domains produced by the present invention can be tuned in a variety of ways. One such method is via incorporation of nonreactive homopolymer into the reaction mixture in order to fortify the domain formed by the macroCTA. In other words, a combination of both PBA _n -CTA and PBA _n may be used in the resin composition for example. The nonreactive homopolymer may be the same or different to the monomer used to prepare the macroCTA, so long as the properties (such as the hydrophobicity) are compatible. The nonreactive homopolymer of the present invention may be found in the resin at concentrations of between about 0 to 30 wt% of the total weight of the resin, or between about 0 and 20 wt%, or between about 5 and 15 wt%, or between about 10 and 20 wt%, or between about 7 and 35 wt%, for instance about 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30 wt% of the total weight of the resin. When incorporated into the cured resin, the inventors refer to the parameter r _macroCTA , which is defined by equation (1) below. where WPBA _n -CTA and WPBA _n represent the weight fractions of PBA _n -CTA and PBA _n respectively and n is as defined above. Accordingly, the r _macroCTA value for any cured resin may be between about 0.00 and 1.00, between about 0.00 and 0.50, or between about 0.25 and 0.75 or between about 0.50 and 1.00, or between about 0.75 and 1.00, for example, 0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95 or 1.00, or any range in between. In a preferred embodiment, the r _macroCTA is 0.75. In another preferred embodiment, the r _macroCTA is 1.00. As the skilled person will appreciate, equation (1) can be adapted for any resin, with the weight fraction of PBA _n -CTA and PBA _n substituted appropriately. Without wishing to be bound by any theory, the present inventors have found that in general, a higher r _macroCTA produced articles with greater strength, toughness and ductility. The inventors understand this to be due to a more efficient microphase separation rather than macrophase separation. [00079] Accordingly, in one embodiment of the present invention, there is provided a resin comprising: between about 5 and 55 wt% PBA _n -CTA, between about 20 and 55 wt% AA, between about 15 and 45 wt% PEGDA, between about 0.1 and 1.0 wt% TPO, whereby the r _macroCTA is between about 0.00 and 1.00. In another embodiment of the present invention, there is provided a resin comprising: between about 10 and 20 wt% PBA _n -CTA, between about 40 and 50 wt% AA, between about 33 and 43 wt% PEGDA, between about 0.1 and 0.5 wt% TPO, whereby the r _macroCTA is between about 0.00 and 1.00. In one embodiment of the present invention, there is provided a resin comprising: between about 25 and 35 wt% PBA _n -CTA, between about 35 and 45 wt% AA, between about 28 and 38 wt% PEGDA, between about 0.3 and 0.7 wt% TPO, whereby the r _macroCTA is between about 0.00 and about 1.00. In one embodiment of the present invention, there is provided a resin comprising: between about 40 and 50 wt% PBA _n -CTA, between about 25 and 35 wt% AA, between about 20 and 30 wt% PEGDA, between about 0.5 and 0.9 wt% TPO, whereby the r _macroCTA is between about 0.00 and 1.00. Uses [00080] The process of the present invention utilises additive manufacturing. As the skilled person would appreciate, the phrase “additive manufacturing” refers to a range of techniques for the construction of three-dimensional objects from a digital or CAD model, whereby the objects are manufactured through the selective deposition, joining or solidification of material (that is, addition) under the control of a computer. “Additive manufacturing” may also commonly be referred to as “3-D printing”. As the skilled person would appreciate, there are a wide variety of additive manufacturing techniques available, which generally fall into the categories of (1) vat photopolymerisation; (2) material jetting; (3) binder jetting; (4) material extrusion; (5) powder bed diffusion; (6) sheet lamination; and (7) directed energy deposition. The inventors have developed the present invention utilising vat photopolymerisation techniques, however it is envisioned that any technique that uses light-curable polymer resins, and particularly visible light-curable resins, would be suitable for use in the present invention. [00081] The process of the present invention uses a light-based additive manufacturing device, preferably a visible light-based additive manufacturing device. By “visible light-based device”, it is meant that the device uses visible light to form each layer of the article. This is distinguished from other additive manufacturing devices that utilise UV-light. The device may utilise a vat photopolymerisation technique, such as stereolithography (SLA), low force stereolithography (LFS) or digital light projection (DLP). In one preferred embodiment, the device may be a DLP device. As the skilled person will appreciate, a DLP device utilises visible light to cure a thin layer of a photocurable resin in a particular pattern controlled by a light projector. Advantageously, as DLP devices do not require components such as lasers or galvanometers (such as those required by SLA devices), they tend to be less expensive, although resins that can be cured with visible light are required. In one embodiment, the resin of the present invention as described herein is loaded into an additive manufacturing device and used according to convention for that device. By way of example, the resin may be loaded into a commercially available DLP 3D printer with a 405 nm light source and an intensity of 0.81 mW/cm ² and the article printed in slices of between about 10 μm and 100 μm in thickness with a cure time per layer of between about 60 seconds and 240 seconds. However, the skilled person will appreciate that layer thickness and curing time may be dependent on a range of factors, such as the specific components of the resin, the wavelengths of light absorbed by the components of the resin, speed of the polymerisation reaction and intensity of the projected light. It is anticipated that the parameters of the additive manufacturing device can be optimised by the skilled person to suit a particular resin. [00082] The resin of the present invention has been developed with the intention of forming robust articles with tuneable flexibility. By “robust” it is meant that the article can withstand significant stress before failure. Robustness may be measured by, for instance, the tensile stress at break of the material. The skilled person would understand that the tensile stress at break of a material is identified as the tensile stress applied at failure of the material, which is commonly known in the field of material science. Preferably, a robust article of the present invention has an tensile stress at break of at least 10 MPa, or at least 15 MPa, or at least 20 MPa, or at least 25, for example. [00083] By “flexible”, it is meant that the material is able to be bent, forced out of shape or deformed; put differently, flexible is the opposite of “rigid”. By “tuneable flexibility” it is meant that by modifying parameters of the resin, the flexibility can be either increased or decreased. The skilled person would appreciate that flexibility is measured by having a relatively high elongation at break, measured as the percentage extension of a material before failure when tensile load is applied, which is a commonly known parameter in material science. A “relatively high elongation at break” for the articles of the present invention is an elongation at break above about 30%, or above about 35%, or above about 40%, or above about 45%, or above about 50%, or above about 50%, such as between about 10% and 100%, or between about 20% and 80%, or between about 25% and 75%, or between about 20% and 50%, or between about 50% and 100%, for example about 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 100%. [00084] Preferably, the “3D printed” articles of the present invention are also transparent. By “transparent”, it is meant that at least some visible light can pass through such that objects behind can be easily seen. For clarity, the inventors do not intend that the article must be colourless (as components of the resin, such as the RAFT agent, may absorb some visible light wavelengths), the passage of light must not be significantly hindered or distorted. The article material of the present invention may be transparent, or substantially transparent, at a thickness of greater than 4mm, or greater than 5 mm, or greater than 7.5 mm, or between about 5 mm and about 10 mm, or about 4, 5, 6, 7, 8, 9, or 10 mm or any range therein. Transparency of an article may be measured by any suitable means known in the art. Generally, transparency (which may also be referred to as transmittance) is measured by comparing the amount of light that passes through a material relative to the amount of light provided to it (that is, the fraction or percentage of light that “successfully” passes through the article). The transparency or transmittance may be measured at any visible wavelength of light (that is, between about 400 nm and 700 nm in wavelength), however preferably it is measured at a wavelength that components of the article do not absorb (if the article is coloured). For example, if the article is yellow-coloured (and so likely to absorb wavelengths of light between 420 and 430 nm), the transmittance is best measured at the red end of the spectrum (i.e., between about 550 nm and 700 nm). The measured transmittance of a transparent article of the present invention may be at least about 20%, or at least about 30%, or at least about 40%, such as between about 10% and 80%, or between about 15% and 50%, or between about 20% and 100%, or about 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 99 or 100% or any range therein. In some embodiments, the transmittance may be between about 30% and about 50%. [00085] Articles produced by curing the resin of the present invention in an additive manufacturing process may be used for a variety of applications that require a combination of nanoscale or microscale structured materials and reproducible shapes. For example, it is envisioned that articles produced by the present invention may be used as nanoporous materials (such as a membrane) or as biomedical materials (such as drug releasing microneedles). The use of common additive manufacturing devices means that the articles produced by the present invention may be obtained in a cost-effective and commercially-advantageous manner. Examples [00086] The present invention will be further described with reference to the following non- limiting worked examples. Example 1 – Optimisation of macroCTA Materials [00087] Unless otherwise stated, all chemicals were used as received. The solvents were of either HPLC or AR grade; these included acetonitrile (RCI Labscan Limited, RCI Premium) and N,N-dimethylacetamide (DMAc, RCI Labscan Limited, HPLC). Aluminium oxide basic (Acros Organics, Brockmann I, 50–200 μm, 60A), 2-(n-butylthiocarbonothioylthio)propanoic acid (BTPA, Boron Molecular, >95%), diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (TPO, Sigma-Aldrich, >97%), 2,2’-azobis(2-methylpropionitrile) solution (AIBN solution, Sigma- Aldrich, 0.2 M in toluene), acrylic acid (AA, anhydrous, Sigma-Aldrich, 99%) and poly(ethylene glycol) diacrylate average Mn = 250 (PEGDA, Sigma-Aldrich, >92%) were used as received. n- butyl acrylate (BA, Sigma-Aldrich, ≥99%) was passed through a basic aluminium oxide column to remove inhibitor prior to use. Synthesis of PBA _n -CTA [00088] A general scheme for synthesizing PBA _n -CTA of the present invention is provided by Scheme 1 below: Scheme 1: Synthesis of PBA _n -CTA using RAFT polymerization of n-butyl acrylate. [00089] An exemplary method for synthesizing PBA24-CTA is provided below. This method can be adapted to produce PBA _n -CTA of varying lengths (hence values of n). [00090] BTPA RAFT agent (5.21 g, 2.2×10-2 mol), n-butyl acrylate (70 g, 0.546 mol) and AIBN (0.2 M solution in toluene, 16.4 mL, 3.3×10-3 mol) were dissolved in acetonitrile (125 mL). The mixture was deoxygenated by purging with nitrogen for 90 min, and then polymerized for 15 h at 60°C. The reaction was stopped by cooling inside a freezer (-20°C) for 30 min and exposing to air. The polymer solution was concentrated by rotary evaporation and used without further purification. Using the same protocol, other PBA _n -CTAs were synthesized. Characterisation [00091] Synthesized PBA _n -CTAs were characterized by Nuclear Magnetic Resonance (NMR) and size exclusion chromatography (SEC) by the following methods. [00092] NMR: All NMR spectra were recorded on Bruker Avance III 400 MHz spectrometer using an external lock (CDCl3). [00093] SEC: Analysis of the molecular weight distributions of the polymers were determined using a Shimadzu modular system composed of an SIL-20A auto-injector, a Polymer Laboratories 5.0 μm bead-size guard column (50 × 7.5 mm ² ) followed by three linear PL (Styragel) columns (105, 104 and 103), an RID-10A differential refractive-index (RI) detector, and a UV detector. The eluent was DMAc (containing 0.03% w/v LiBr and 0.05% w/v 2,6- dibutyl-4-methylphenol (BHT)) at 50°C, run at a flow rate of 1.0 mL/min. The SEC was calibrated using narrow polystyrene (PSTY) standards with molecular weights of 200 – 10 ⁶ g/mol. [00094] The characterizations for the synthesized PBA-CTAs are summarized in Table 1 below. Monomer conversion was calculated by ¹ H NMR by comparing integrals of polymers (4.05 ppm) and residual monomers (~ 6 ppm). M _n (theory) was calculated using the following equation: ([BA]/[BTPA]) × conv. (BA) × MW(BA) + MW(BTPA). The degree of polymerization (X _n ) of PBA-CTAs was calculated based on the integral value at 4.05 ppm, X _n = I _4.05 /2. Mn (NMR) was calculated using the following equation: X _n (PBA-CTA) × MW(BA) + MW(BTPA). End group fidelity was calculated using the following equation: f (%) = I _4.8 /(I _3.35 /2) × 100%, where I _3.35 and I _4.8 are integral values at 3.35 and 4.8 ppm, respectively. Table 1: Characterization of PBA-CTAs synthesized by RAFT-mediated polymerization of n- butyl acrylate in acetonitrile. [00095] Altogether, well-defined PBA-CTAs were successfully prepared by RAFT polymerization, allowing us to investigate the effect of PBA-CTA chain length on model polymerization kinetics. Material Analysis - Kinetics [00096] Subsequently, 15 resins were formulated by mixing AA, PEGDA, PBA-CTA and TPO in predetermined weight ratios to form homogeneous, transparent mixtures, as shown in Table 2 below.

Table 2: Resin formulations with varying degree of polymerization (X _n ) of PBA-CTA and corresponding conversions of 3D printed objects. The molar ratio of [AA]/[PEGDA] was fixed at 4:1. The degree of polymerization of PBA-CTA was determined by ¹ H NMR as above. Resin conversion (%) was measured by comparing printed samples to uncured resins using FTNIR analysis. [00097] The photopolymerization kinetics of each resin was then determined in open-air conditions. The molar ratio of [AA]/[PEGDA] was fixed at 4:1 and the mass loading of PBA- CTA in the resins was varied between 16.5, 28.2 and 43.9 weight percent (wt%). The concentration of TPO was kept constant for resins with the same PBA-CTA wt%, specifically at 0.3, 0.5 and 0.7 wt% for 16.5, 28.2 and 43.9 wt% of PBA-CTA, respectively. All resin formulations demonstrated gelation within 60 s without a noticeable inhibition period, however, resins that contained macroCTAs with lower chain lengths (X _n = 24 and 48) displayed slightly slower polymerization kinetics (Fig.2). For example, the resin loaded with 16.5 wt% of PBA24- CTA showed 29.9% double bond conversion (α) after 30 s of irradiation and α = 78.9% after 60 s (see Figure 3(a)). Comparatively, using PBA94-CTA at 16.5 wt% loading resulted in α = 77.8% and 87.0% after 30 and 60 s of irradiation, respectively. Further increasing the macroCTA chain length to 180 and 360 repeating units of BA negligibly affected double bond conversion profiles, with these systems reaching high monomer conversions after 30 and 60 s with α ≈ 84% and 91%, respectively. Similar trends in polymerization kinetics were observed for the 28.2 and 43.9 wt% systems (see Figure 3(b) and (c)). The slight reduction in polymerization rate for resins with low macroCTA chain lengths (X _n = 24 and 48) can be explained by the increased concentration of RAFT end-groups. Regardless, all resins demonstrated fast double bond conversion upon irradiation and appeared to be suitable for 3D printing. Material Analysis - Morphology [00098] A typical procedure for fabricating 3D printed objects is as follows: A 3D object was designed using Tinkercad 3D modelling software and the object was exported as an .stl file. The .stl file was opened using Photon Workshop where the Z lift speed was set to 3 mm/s and Z retract speed was set to 2 mm/s, while the Z lift distance was set to 6 mm. Printing parameters, such as layer thickness and exposure time, were defined in Photon workshop, sliced, and exported as .pws files for 3D printing. The .pws file copied to a flash drive for use with a masked DLP 3D printer (Anycubic Photon S) with a violet (λmax = 405 nm) light LED array (I ₀ = 0.4 mWcm ^-2 , as measured at the digital mask surface using a Newport 843-R power meter). For 3D printed samples for DMA and tensile tests, layer thickness was 100 μm, off time was 2 s, layer and bottom exposure times were 180 s, number of bottom layers was 2. Typical 3D printing resin formulations were prepared by combining the calculated amounts of PBAn-CTA, AA, PEGDA and TPO (see Table 2). It should be noted that the amount of inhibitor contained in AA and PEGDA was compensated by the addition of extra TPO in a 1:1 molar ratio. The resin was then added to the 3D printer vat, and the desired print program was run. After 3D printing was completed, the printed objects were separated from a build plate, washed with ethanol, air dried, and post-cured under violet light (λ _max = 405 nm) for 15 min. [00099] To investigate the effect of PBA X _n and wt% on the nanostructure of 3D printed materials, the 15 resins were applied to a commercial DLP 3D printer to fabricate model rectangular prisms (l × w × t = 40 × 8 × 2 mm). For comparison, the layer thickness and layer cure time for all the prints were set to 100 μm and 180 s/layer, respectively. All 3D printed materials were well-defined transparent rectangular prisms with high vinyl bond conversions (α > 91%) (see Table 2). After a 15 min post-cure treatment, the surface of 3D printed materials was examined by AFM to determine the formation of different microphase separated morphologies. PeakForce tapping mode was used to distinguish between domains with different mechanical properties, i.e., soft PBA domains (with a low modulus) and hard net-P(AA-stat- PEGDA) domains (with a high modulus). [000100] All AFM measurements were performed on the Bruker Dimension ICON SPM, with a Nanoscope V controller (software version 9.70). An OTESPA-R3 probe (from Bruker AFM probes) was used to perform the tapping mode measurements. Mechanical properties measurements were performed using peak force tapping mode on a top layer of printed object using the SCANASYST probe (from Bruker AFM probes). The scan size was set to 1 μm and 300 nm. The scan rate was set at around 0.6 to 0.7 Hz with a peak force of approximately 500 pN. The feedback gain was adjusted accordingly to optimize tracking of the specimen surface, without any significant feedback noise. The resolution of the image was set to 512 pixels per line for 1 μm scan size and 256 samples/line for 300 nm scan size. For peak force QNM measurements, the tip was calibrated using the thermal tunning method. AFM images were analysed using NanoScope Analysis software, version 1.7. For the statistical length analysis, at least 50 particles were carefully traced by hand to determine average domain size and domain spacing using ImageJ software. Histograms of the size distribution were constructed. Average PBA domain width (D), domain length (L) and domain spacing (d) were calculated using Equation 2: where N is the number of observations and d is the determined size for each measurement. [000101] SAXS experiments were performed on an Anton Paar SAXSPoint 2.0 system with a Cu Kα (λ = 0.154 nm) microfocus X-ray source (50 kV/1 mA) and Dectris Eiger 1M detector. Data was collected at room temperature, under vacuum for 5 min from a sample at a sample-to- detector distance of 0.575 m. Samples were 3D printed at the thickness of 2×100 μm layers. Data was reduced to 1D by radial averaging the 2D detector after converting pixel positions to q = (4π/λ)sinθ, where 2θ is the scattering angle). The domain spacing was calculated using Equation 3: [000102] The morphology of the 3D printed materials is summarized below in Table 3. Table 3: Summary of morphology characterization for 3D printed PIMS materials. Morphology of 3D printed materials determined by AFM. PBA domain width (D _PBA ), PBA domain length (L _PBA ) and domain spacing (d _AFM ) determined from AFM. d _AFM values for X _n = 24 were not reported due to difficulty in precise measurement. Domain spacing (d _SAXS ) determined from SAXS. [000103] As can be seen, a clear morphological evolution was observed upon increasing the X _n of the PBA block. For materials 3D printed with 16.5 wt% of PBA-CTA and with X _n = 24 and 48, we observed the formation of discrete globular PBA domains dispersed in the continuous net-P(AA-stat-PEGDA) network. Further increasing the X _n of the PBA block to 94 resulted in the formation of elongated PBA domains, while at X _n = 180 and 360, we observed bicontinuous morphologies. Close inspection of these AFM images revealed that the PBA domain width (D _PBA ) and domain spacing (d _AFM ) monotonically increased from 7 to 23 nm and from 19 to 55 nm, respectively, with increasing X _n of the PBA block. Similar morphological evolutions were observed upon increasing PBA-CTA X _n for materials 3D printed using resins with 28.2 and 43.9 wt% PBA-CTA. Materials with distinct globular PBA domains were observed when using PBA- CTA X _n = 24, while elongated globular aggregates of PBA domains were observed in materials 3D printed using PBA-CTA X _n = 48. When using resins with larger PBA-CTA chain lengths (X _n = 94, 180, and 360), materials with bicontinuous morphologies were obtained. [000104] As an overall trend for materials 3D printed using the PIMS process, as the X _n of PBA block increased from 24 to 360, D _PBA and dAFM increased from 7 to 22 nm and from 15 to 45 nm, respectively. In addition, tan δ profiles for the objects 3D printed using 28.2 and 43.9 wt% PBA- CTA exhibited two separate peaks at around −35 and 75 °C associated with the glass transitions of the PBA-rich phase and the net-P(AA-stat-PEGDA) phase, respectively, thus confirming the formation of microphase-separated morphologies. These materials also demonstrated a drop in the storage modulus (G’) near -40 °C due to the glass transition of the PBA domains. The gradual decrease in G’ continued with increasing temperature until the materials softened around 100 °C, likely due to passing through the glass transition of the net-P(AA-stat-PEGDA) domains. [000105] Altogether, AFM results showed a clear morphological transition from globular to more continuous morphologies, i.e., elongated domains, and further to bicontinuous morphologies with increasing PBA-CTA Xn. In PIMS processes, the material morphology is dictated by competition between the thermodynamic forces driving microphase separation of the chemically incompatible blocks and the kinetic arrest of the network due to the in-situ crosslinking and gelation. Material Analysis – Mechanical Behaviour [000106] Having demonstrated the effect of PBA-CTA chain length on nanostructured material morphologies, the bulk mechanical properties of the 3D printed materials were examined according to the following methods. [000107] Tensile testing: Dog-bone specimens were designed using Tinkercad 3D modelling software by modifying ASTM D638 Type I specimen and the object was exported as an .stl file. Specimen dimensions were thickness (T) = 2.04 mm, width overall (WO) = 8.38 mm, length overall (LO) = 50.3 mm, distance between grips (D) = 36 mm, gage length (G) = 15.79 mm, width at the centre = 6 mm. The mechanical tensile stress tests were performed using a Mark–10 ESM303 with a 1 kN force gauge model M5–200. The speed of testing was 1.1 mm/min. All tensile results were performed in triplicate. The tensile stress was calculated from the applied force divided by the initial cross-sectional area of the gage section. The strain was determined as the change in gage length relative to the original specimen gage length, expressed as a percent. Toughness was determined by calculating the area under a stress-strain curve using the trapezoidal rule. [000108] The results of these mechanical tests are shown in Table 4 below.

Table 4: Summary of mechanical properties for 3D printed PIMS materials. Tensile stress at break was reported as the maximum tensile strength immediately before break. Elongation at break was reported as the maximum elongation of the sample immediately before break. Toughness was determined by calculating the area under a stress-strain curve using the trapezoidal rule. [000109] As can be seen from Table 4, upon increasing PBA-CTA X _n from 24 to 94, the materials 3D printed using the method above and with 28.2 and 43.9 wt% of PBA-CTA demonstrated similar values of stress at break (σ _B ), while the material 3D printed with 16.5 wt% of PBA-CTA showed increased σ _B from 38.7 to 48.1 MPa. Within the same range of PBA-CTA X _n , the elongation at break (ε _B ) for all materials increased, with the highest increase from 40.7 to 91.4 % observed for the material 3D printed with 16.5 wt% PBA-CTA. Consequently, the toughness of this material increased by nearly three-fold, from 13.3 to 35.5 MJ m ^-3 , whereas materials 3D printed with higher loadings of PBA-CTA (28.2 and 43.9 wt%) exhibited slightly increased toughness. The improvement in material mechanical properties, particularly notable for materials 3D printed with a lower loading of PBA-CTA (16.5 wt%), can be attributed to the morphology transition from discrete globular PBA nanodomains dispersed in the net-P(AA-stat- PEGDA) matrix, to more continuous, interpenetrating soft PBA and hard net-P(AA-stat- PEGDA) nanodomains, thus allowing a more even distribution of stress throughout the material. Further increasing the PBA-CTA X _n from 94 to 360 resulted in an overall reduction in mechanical properties, with the higher PBA-CTA wt% materials showing a more pronounced decrease. For example, while the 16.5 wt% PBA-CTA system showed only marginal decreases in σ _B from 48.1 to 47.0 MPa upon increasing X _n from 94 to 360, the 43.9 wt% system showed a larger decrease from 15.6 to 10.1 MPa. The ε _B also dramatically decreased for the 43.9 wt% PBA-CTA material, from 99.5% for the PBA ₉₄ -CTA material, to 55.0% for PBA ₃₆₀ -CTA material. Consequently, the material toughness decreased more significantly for the 43.9 wt% system compared to the 28.2 and 16.5 wt% systems. We postulated that the mechanical properties changes that occurred with changing X _n and PBA-CTA wt% were related to the domain size variations. To more closely examine this, σB, ε _B and toughness were plotted as functions of D _PBA and domain d _SAXS for two types of interpenetrating morphologies, i.e., elongated domains and bicontinuous morphologies. [000110] The decrease in the mechanical properties of the 3D printed materials with bicontinuous phase structure correlated with an increase in d _SAXS . For example, the material 3D printed with 43.9 wt% of PBA ₉₄ -CTA exhibited a bicontinuous morphology with d _SAXS = 18 nm; σB, ε _B , and toughness of this material were 15.6 MPa, 99.5% and 12.4 MJ m ^-3 , respectively. As the d _SAXS values increased to 43 nm for the bicontinuous material 3D printed using 43.9 wt% of PBA ₃₆₀ -CTA, σ _B decreased to 10.1 MPa while ε _B and toughness decreased to 55.0% and 4.4 MJ m ^-3 , respectively. The same correlation of material mechanical properties with D _PBA was observed. These results are as expected and can be explained as follows: at a fixed weight loading of PBA-CTA, an increase in domain size and domain spacing reduces the interfacial area between soft and hard domains. This consequently reduces the efficiency of localized stress dissipation from hard to soft domains and lowers the amount of absorbed deformation energy required to cause fracture of a material. [000111] Altogether, the mechanical properties of 3D printed materials with interpenetrating soft and hard domains, i.e., elongated domains and bicontinuous morphology, with length scales of D _PBA ~13 nm and d _SAXS ~20 nm were higher than similar materials with globular morphologies. However, further increasing in the d _SAXS of bicontinuous materials resulted in reduced mechanical properties due to reduced interaction between soft and hard domains and lower dissipation of localized stress throughout the material. Material Analysis – Macroscale Geometric Control [000112] To demonstrate the capability of RAFT-mediated PIMS 3D printing to fabricate complex objects that are challenging to produce via traditional manufacturing approaches, a cubic lattice structure with target strut width of 0.9 mm was designed and 3D printed as per the method above. Three PIMS resins were formulated with the molar ratio of [AA]/[PEGDA] = 4:1 and 28.2 wt% of PBA-CTA with X _n = 48, 94 and 180. The layer cure time was set to 25 s/layer and the layer thickness was 100 μm, which represents a reasonably practical build rate of 1.44 cm h ^-1 . For all formulated resins the 3D printed cubic lattice structures replicated the original CAD model with high printing fidelity. The measured strut width of the 3D printed lattice was 0.8 mm as measured by a digital calliper, which is slightly lower than the target value of 0.9 mm. This is due to volume layer shrinkage commonly observed for acrylate resins. Example 2 – Nanoscale Control Materials [000113] The solvents were of either HPLC or AR grade; these included acetonitrile (RCI Labscan Limited, RCI Premium) and N,N-dimethylacetamide (DMAc, RCI Labscan Limited, HPLC). Aluminium oxide basic (Acros Organics, Brockmann I, 50–200 μm, 60A), 2-(n- butylthiocarbonothioylthio)propanoic acid (BTPA, Boron Molecular, >95%), diphenyl (2,4,6- trimethylbenzoyl) phosphine oxide (TPO, Sigma-Aldrich, >97%), 2,2’-azobis(2- methylpropionitrile) solution (AIBN solution, Sigma-Aldrich, 0.2 M in toluene), acrylic acid (AA, anhydrous, Sigma-Aldrich, 99%) and poly(ethylene glycol) diacrylate average Mn = 250 (PEGDA, Sigma-Aldrich, >92%) were used as received. n-butyl acrylate (BA, Sigma-Aldrich, ≥99%) was passed through a basic aluminium oxide column to remove inhibitor prior to use. Synthesis of PBA ₄₈ -CTA [000114] A general scheme for synthesizing PBA _n -CTA of the present invention is provided by Scheme 2 below. Scheme 2: Synthesis of PBAn-CTA (n = 24, 48, 94) using RAFT polymerization of n-butyl acrylate. [000115] An exemplary method of preparing a macroCTA via RAFT-mediated polymerisation of n-butyl acrylate with BTPA is given below. Although this method is for PBA ₄₈ -CTA (where n=48), it will be appreciated that the skilled person could adapt this method to any n value by adjusting the relative amount of BA and BTPA. [000116] PBA ₄₈ -CTA was synthesized as follows: n-butyl acrylate (100 g, 0.78 mol), BTPA RAFT agent (3.72 g, 1.6×10-2 mol) and AIBN (0.2 M solution in toluene, 11.7 mL, 2.3×10 ^-3 mol) were dissolved in acetonitrile (190 mL). The mixture was deoxygenated by purging with nitrogen for 90 min, and then polymerized for 14.5 h at 60°C. The reaction was stopped by cooling inside a freezer (-20°C) and exposing to air. The polymer solution was concentrated by rotary evaporation and used without further purification. Using the same protocol, other PBA _n - CTAs (n = 24, 94) were synthesized. Five PBA _n -CTAs prepared by adapting the above method and their characterisation is summarized in Table 5. Table 5: Characterization of PBA _n -CTAs synthesized by RAFT-mediated polymerization of n- butyl acrylate in acetonitrile. Material Preparation [000117] Samples were prepared to determination of reaction kinetics and for suitability for use in a 3D printing device, as set out below. [000118] A range of resin formulations were prepared according to the method of the present invention, as shown in Table 6. Resins 1-4 shown below illustrate compositions with varying amounts of PBA ₄₈ -CTA, resins 5-6 illustrate compositions using PBA ₂₄ -CTA and PBA ₉₄ -CTA as the macroCTA, resins 7-12 are comparative resins absent the macro-CTA and resins 13-15 use various ratios of PBA ₄₈ -CTA to unreactive PBA ₄₈ (variable r _macroCTA values). The conversion % was measured by comparing printed samples to uncured resins using FTNIR analysis. Table 6: Resin formulations for RAFT mediated PIMS 3D printing with increasing wt% of PBA ₄₈ -CTA (unless otherwise defined) and corresponding conversions of 3D printed objects.

Materials analysis - Kinetics [000119] For the reaction kinetics experiments, typical polymerization solutions were prepared as follows: 0.267 g of PBA ₄₈ -CTA (0.041 mmol, 1 eq.) was weighed in a 1.5 mL Eppendorf tube, followed by addition of 0.337 mL AA (4.9 mmol, 120 eq.) and 0.277 mL PEGDA (1.23 mmol, 30 eq.) followed by the addition of 5.1 mg of TPO (0.012 mmol, 0.3 eq.). It should be noted that the amount of inhibitor contained in AA and PEGDA was compensated by the addition of extra TPO in a 1:1 molar ratio. The reaction mixture was then covered in aluminium foil, vortexed for 20 s prior to irradiation using the protocol described in section 4.3. Resins with different formulations were prepared using the same method while the amount of TPO was varied to obtain desired ratios. [000120] The photopolymerization kinetics of each resin formulation was investigated to ensure reasonable build speeds could be achieved during 3D printing. In the kinetics experiments, a 20 μL droplet of resin was irradiated with a Thorlabs mounted LED with a collimation adapter (λmax = 405 nm, I0 = 2.06 mW cm-2) for 2 min. The resin was scanned at 15 s intervals between 0 to 2 min using ATR-FTR spectroscopy. The conversion was determined by observing disappearance of the vinyl bond (=C−H) peak at 1630 cm ^-1 (see Figure 4). Incrementally increasing the TPO concentration resulted in an increased polymerization rate, with the 0.3 equiv. TPO system showing the fastest vinyl bond conversion (α) after 30 and 60 s with α = 81% and 92%. The concentration of TPO was not increased further to ensure sufficient light penetration through the resin and restrict the generation of free P(AA-stat-PEDGA) copolymers. Pleasingly, each of the resins tested showed a high conversion (α > 80%) after 60s of irradiation (see Table 6), which indicates suitable processability with a light-mediated 3D printing setup. Materials Analysis - Mechanical Properties [000121] The bulk mechanical properties of the 3D printed materials were also examined by tensile testing, with the materials featuring phase-separated morphologies displaying consistently higher toughness and elongation at break (ε _B ) values compared to the non-phase-separated materials formed via terpolymerization. [000122] A typical procedure for fabricating 3D printed objects is as follows: A 3D object was designed using Tinkercad 3D modelling software and the object was exported as an .stl file. The .stl file was opened using Photon Workshop where the Z lift speed was set to 3 mm/s and Z retract speed was set to 2 mm/s, while the Z lift distance was set to 6 mm. Printing parameters, such as layer thickness and exposure time, were defined in Photon workshop, sliced, and exported as .pws files for 3D printing. The .pws file copied to a flash drive for use with a masked DLP 3D printer (Any cubic Photon S) with a violet (λmax = 405 nm) light LED array (I0 = 0.81 mWcm-2, as measured at the digital mask surface using a Newport 843-R power meter). For 3D printed samples for DMA and tensile tests, layer thickness was 100 μm, off time was 2 s, layer and bottom exposure times were 180 s, number of bottom layers was 2. Typical 3D printing resin formulations were prepared by combining the calculated amounts of PBA ₄₈ -CTA, PBA ₄₈ , BTPA, AA, BA, PEGDA and TPO (see Scheme 3). It should be noted that the amount of inhibitor contained in AA and PEGDA was compensated by the addition of extra TPO in a 1:1 molar ratio. The resin was then added to the 3D printer vat, and the desired print program was run. After 3D printing was completed, the printed objects were separated from a build plate, washed with ethanol and post-cured under violet light (λmax = 405 nm) for 15 min. Scheme 3: Photoinitiated RAFT copolymerization of AA and PEGDA in the presence of PBAn- CTA and TPO, as performed in the DLP 3D printer. [000123] Tensile strength measurements were carried out as per the method provided in Example 1 above. The results of these analyses are in Table 7, whereby resin # corresponds to the same resins as in Table 6.

Table 7: Summary of morphology characterization and mechanical properties for 3D printed PIMS materials and corresponding control materials. Resulting morphology of 3D printed materials, as determined by AFM in tapping mode; average size of PBA domains and PBA inter- domain distances was determined by carefully measuring at least 50 particles. Tensile stress at break was reported as the maximum tensile strength immediately before break. Elongation at break was reported as the maximum elongation of the sample immediately before break. Toughness was determined by calculating the area under a stress-strain curve using the trapezoidal rule. [000124] For example, materials 3D printed with 16.5 wt% PBA48-CTA showed an εB of 71.2% and a toughness of 24.9 MJ m ⁻³ , which was significantly higher than the corresponding material 3D printed with the macroCTA free formulation, which showed an ε _B of 50.8% and a toughness of 12.0 MJ m ⁻³ . The bicontinuous nanostructured materials 3D printed with 28.2 wt% and 43.9 wt% PBA ₄₈ -CTA also showed enhanced toughness and elongation at break values compared to their non-phase separated counterparts. Moreover, nanostructured materials containing PBA (resins 1-3) exhibited better mechanical properties compared to materials printed in the absence of PBA (resins 9-12), demonstrating an increase in εB, from 40.5% to 63.0%, and a 24% increase in toughness to 16.7 MJ m ⁻³ . In addition, the bulk mechanical properties of these 3D printed materials can be tuned by changing the PBA ₄₈ -CTA weight percentage in the resins. Lowering the loading of PBA ₄₈ -CTA from 28.2 wt% to 16.5 wt% resulted in materials with increased tensile stress at break (σB) from 31.2 to 40.7 MPa, slightly increased εB from 63.0% to 71.2%, and a correspondingly increased toughness, from 16.7 to 24.9 MJ m ⁻³ . Higher loadings of PBA ₄₈ -CTA(43.9 wt%) also significantly improved the material ductility, with this material showing the highest εB value of any tested sample (94.7%), albeit at the cost of a reduced σB. [000125] Having successfully demonstrated the 3D printing of nanostructured materials via PIMS, we turned our attention to the fabrication of larger materials with more complex macroscale architectures. Indeed, the ability to fabricate geometrically complex materials has largely driven the widespread adoption of 3D printing and is considered a basic requirement for new systems. To demonstrate this concept, a 7.2 cm tall continuous gyroid egg sculpture was 3D printed using the formulation of Resin #3 described above in Table 6. The slicing thickness and layer cure time were set as 100 μm per layer and 60 s; this represents a practical build speed of 6.0 mm h ⁻¹ . Pleasingly, the 3D printed gyroid egg provided a faithful reproduction of the original design, including fine curvature at the edges of the material and throughout the continuous macroscale architecture. To demonstrate the ability to form sub-millimetre sized features using this commercial 3D printer, a resolution test was performed for the two systems which displayed bicontinuous morphologies, that is, systems with 28.2 wt% and 43.9 wt% PBA ₄₈ -CTA. Both resins were capable of producing segregated pillars, ridges, and valleys, with characteristic lengths on the order of 200 μm. Under the tested printing conditions the higher viscosity 43.9 wt% PBA ₄₈ -CTA resin was able to produce smaller protruding features more accurately, while the lower viscosity 28.2 wt% PBA ₄₈ -CTA resin was more effective for the fabrication of sunken features. Regardless, both systems were capable of producing submillimeter features, which can be further miniaturized via the use of higher resolution 3D printers. Material Analysis – Controlling Nanostructures [000126] Another series of resins with varied weight ratios of PBA ₄₈ -CTA to unreactive PBA ₄₈ were prepared (resins 13-15). The ratio of PBA _n -CTA to PBA (r _macroCTA ) is calculated per Equation 1 above, whereby Resin 7 has a r _macroCTA value of 0, Resin 13 has a r _macroCTA value of 0.25, Resin 14 has a r _macroCTA value of 0.5, Resin 15 has a r _macroCTA value of 0.75 and Resin 2 has a _rmacroCTA value of 1. [000127] A rectangular prism 3D printed using only a mixture of PBA48 with BTPA (r _macroCTA = 0.00) was essentially opaque, indicating macrophase separation between the PBA and net-P(AA- stat-PEGDA) domains. At r _macroCTA value of 0.25 the 3D printed rectangular prism showed slightly increased transmittance, while the samples with r _macroCTA > 0.50 showed high transparency. These observations are consistent with previous work reported for cross-linked monoliths prepared by bulk RAFT polymerization and are explained by changes in the characteristic length scale of phase-separated structures from microdomains to nanodomains upon increasing r _macroCTA from 0.00 to 1.00. [000128] To investigate the phase separation behaviour, tanδ profiles of the rectangular prisms from −70 to 150 °C were evaluated via dynamic mechanical analysis. DMA was performed using a single cantilever bending test. The sample dimensions were 40 mm (length) × 8 mm (width) × 2 mm (thickness). The analysis was performed using a TA instruments Q800 dynamic mechanical analyser which was equipped with a TA instruments liquid nitrogen gas cooling accessory (GCA) for temperature control. Initially, the 3D printed sample was measured using digital callipers and placed into the single cantilever clamp. The clamp was then tightened using a torque wrench with a force of 5 in lb. All experiments were conducted using the following method: equilibration at -70°C, isothermal for 3 min, temperature ramped to 150°C at a rate of 2°C/min, constant frequency of 1 Hz and displacement of 15 μm. Glass transition temperature was determined using the temperature at the peak of the tan δ curve. [000129] Two distinct peaks attributed to net-P(AA-stat-PEGDA) phase (high Tg) and the PBA- rich phase (low Tg) were observed in all cases, indicating the formation of phase-separated domains (see Figure 5). The low temperature tanδ peak showed significantly decreased intensity upon increasing rmacroCTA, suggesting the presence of soft domains with smaller size. The changes in the tanδ curves with increasing rmacroCTA can be attributed to nanoscale morphology variations in the 3D printed materials. To corroborate this, AFM was used to characterize the materials 3D printed using the resins with various rmacroCTA. For the system with r _macroCTA = 0.00, micron-sized agglomerates of PBA-rich domains in net-P(AA-stat- PEGDA) matrix were observed, confirming macrophase separation for this sample. As r _macroCTA increased to 0.25, the PBA phase formed micron-sized clusters consisting of smaller, 66 nm PBA agglomerates, while further increasing rmacroCTA to 0.50 resulted in the generation of discrete and distributed PBA domains with elongated appearance and an average size of 12 nm. SAXS analysis of material 3D printed with rmacroCTA = 0.50 revealed a domain spacing of 24 nm, which is in agreement with AFM analysis. Samples with r _macroCTA of 0.75 and 1.00 showed interconnected PBA domains, forming a bicontinuous structure with average PBA domain sizes of 9 and 7 nm, respectively, and average PBA interdomain distances of 15 and 18 nm, respectively. It should be noted that these values showed some variability and were similar within the margin of error. SAXS analysis of these materials confirmed nanostructural features on the same order as AFM. The material 3D printed with r _macroCTA = 0.75 demonstrated a single broad SAXS peak with the peak position at q* = 0.36 nm ⁻¹ , which corresponds to domain spacing of 17 nm. At r _macroCTA = 1.00, the peak position was observed at q* = 0.45 nm ⁻¹ with a domain spacing of 14 nm. [000130] The differences in phase-separated morphologies and domain sizes with varied r _macroCTA can be explained by variations in the PIMS process during 3D printing, particularly the ability for selective swelling of PBA domains to occur. For samples with r _macroCTA = 1.00, the PIMS process can be considered ideal; the PBA ₄₈ -CTA is efficiently chain extended to form diblock copolymers which begin to microphase separate, forming bicontinuous structures until the morphology is arrested by cross-linking. For systems containing PBA ₄₈ in small amounts, that is, for r _macroCTA = 0.75, the unreactive PBA ₄₈ selectively swells PBA nanodomains generated during PIMS, resulting in a slightly increased domain spacing as observed by SAXS. This trend continues for the r _macroCTA = 0.50 system, however, there is some partial loss of continuity in the PBA phase. At r _macroCTA = 0.25, there is a drastic change in morphology with the formation of PBA agglomerates. In this case, as the high concentration of PBA ₄₈ cannot be accommodated in microphase separated nanodomains, macrophase separation with P(AA-stat-PEGDA) occurs during polymerization; this is reflected in visual observations of opacity in this sample. At r _macroCTA = 0.00, the P(AA-stat-PEGDA) and PBA ₄₈ undergo macrophase separation via a polymerization induced phase separation mechanism until the disordered morphology is kinetically trapped by cross-linking. [000131] Finally, the mechanical and optical properties of the tuneable materials 3D printed using resins with variable r _macroCTA were investigated (see Table 8). Table 8: Summary of morphology characterization and mechanical properties for 3D printed materials as a function of r _macroCTA . [000132] As shown in Table 8, the material 3D printed using only the mixture of PBA ₄₈ and BTPA (r _macroCTA = 0.00) exhibited very poor mechanical properties with ε _B of 8.8% and toughness of 0.3 MJ m ⁻³ . By contrast, the addition of PBA ₄₈ -CTA in even small quantities, that is, r _macroCTA = 0.25, provided significantly stronger, more ductile, and tougher materials, a trend which continued as the r _macroCTA was further increased. At r _macroCTA = 1.00, the material showed high strength (σ _B of 31.2 MPa), ductility (ε _B of 63.0%), and toughness (16.7 MJ m ⁻³ ). These values were only marginally higher compared to the materials 3D printed with r _macroCTA = 0.75, which reflects the similarities in the material morphologies and domain sizes and spacing. The improvements in material toughness with increasing in r _macroCTA are attributed to the increased capability for efficient stress transfer throughout the material. As expected, materials with bicontinuous hard and soft domains are capable of stress transfer among the domains, resulting in more uniform stress distribution and thus alleviation of stress concentration to avoid premature failure. [000133] The 3D printed articles of Table 8 were also analysed optically for their transmittance. Analysis was carried out on a Varian Cary 300 spectrophotometer at wavelengths of between 400 and 700 nm and is summarised in Figure 6. As can be seen, good transmission was recorded to articles of r _mactoCTA values of 0.50 or more, which correlates to the different phase types in these articles (whereby macrophase separation is understood to lead to greater dispersion of light). Example 3 – Polysiloxane CTAs [000134] The macromolecular chain transfer agent may also be based on a polysiloxane polymer chain, as described above. Examples of producing a PDMS _n -CTA and PDMS _n -b-PBA _n -CTA are described below. PDMS-based CTA Synthesis [000135] To from a macroCTA comprising only PDMS, the following exemplary method was used. A solution of N-(3-(dimethylamino)propyl)-N′-ethylcarbodiimide hydrochloride (EDC·HCL; 1.07 g, 5.6 mmol) in dichloromethane (40 mL) was added dropwise to a solution of PDMS-OH (20.0 g, 4.0 mmol), BTPA (1.42 g, 5.96 mmol), and DMAP (0.073 g, 0.6 mmol) in dichloromethane (16 mL) at <10 °C. Following addition, the reaction was allowed to stir for 24 h at room temperature. The red/orange solution was washed with Milli-Q water (5 × 50 mL). The organic layer was dried over MgSO ₄ , concentrated under vacuum, and precipitated in methanol (MeOH). The precipitated product was washed with MeOH twice. The purified product was concentrated under vacuum to afford the product as yellow oil. [000136] To form a co-block polymer macroCTA, the following exemplary method was used. n- butyl acrylate (6.4 g, 0.05 mol), PDMS ₆₇ -CTA as prepared above (2.98 g, 5.0×10 ^-4 mol) and AIBN (0.2 M solution in toluene, 0.4 mL, 7.5×10 ^-5 mol) were dissolved in 1,4-dioxane (12.4 mL). The mixture was deoxygenated by purging with nitrogen for 60 min, and then polymerized for 17 h at 60°C. The reaction was stopped by cooling inside a fridge (0°C) and exposing to air. The polymer solution was concentrated by rotary evaporation and used without further purification. [000137] The PDMS _n -CTA and PDMS _n -b-PBA _n -CTA produced were characterized with ¹ H NMR (as described above), as shown in Figures 7 and 8. [000138] A range of resins were prepared as described in Table 9 below and articles prepared using a typical 3D printing technique as described above. Table 9 also provides the morphological characterisation of these PDMS-CTA-based articles, using AFM and SAXS techniques also as described above. Table 9. Summary of morphology characterization for 3D printed PIMS materials using PDMS- CTAs and PDMS ₆₇ -b-PBA ₈₀ -CTA. ^a – AFM analysis is not reliable due to very low modulus of PDMS phase. Microphase separation was confirmed by SAXS. Abbreviation: IBA – Isobornyl acrylate; HDDA - 1,6-Hexanediol diacrylate; TMPTA - trimethylolpropane triacrylate; AA – Acrylic acid; PEGDA - Poly(ethylene glycol) diacrylate (average M _n 250 g/mol). [000139] As can be seen, macroCTAs based on PDMS (either alone or in a co-block polymer arrangement with PBA) can also form separate domains (as evidenced by the d _SAXS data). Notably, when PDMS is used alone, the material produced can be relatively soft (which prevented AFM measurements being taken), even with the selection of relatively rigid acrylate monomers as the opposing domain. However, this example is a “proof of concept” for the use of polysiloxane-based macroCTAs in an additive manufacturing process. [000140] In conclusion, polymeric multi-materials with nanoscale structuration were successfully fabricated by exploiting PIMS in a commercial DLP 3D printer. The resulting materials, which are inaccessible through traditional synthetic approaches, display tuneable domain spacing and sub-10 nm domain sizes. The mechanical performance of 3D printed materials with analogous chemical compositions was found to be significantly enhanced upon the generation of microphase-separated morphologies, for example, the randomly distributed spherical or bicontinuous. The addition of unreactive homopolymer in conjunction with a macroCTA also affected the in-situ phase separation process, allowing control over 3D printed material nanoarchitectures and resulting material stress–strain behaviour. The strategy presented here represents a versatile and highly attractive process to generate multi-component polymer materials with various morphologies and bulk properties via 3D printing. Due to the versatility of the PIMS approach and the tunability of block copolymer composition and structures, preparation of a rich variety of 3D printed objects with various properties should be possible through this cost-effective and highly accessible approach. This may result in the production of 3D printable electrically conductive polymer composites, nanoporous materials for biomedical applications, functional membranes, and materials for engineering applications, among others. [000141] Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms in particular features of any one of the various described examples may be provided in any combination in any of the other described examples. Various modifications and alterations to this invention will become apparent to those skilled in the art without departing from the scope and spirit of this invention. It should be understood that this invention is not intended to be unduly limited by the illustrative embodiments and examples set forth herein and that such examples and embodiments are presented by way of example only with the scope of the invention intended to be limited only by the claims set forth herein as follows.