Solvation

Field of the Invention

The present invention relates to the use of dihydrolevoglucosenone (hereafter referred to by its trade name, Cyrene™) and ternary mixtures thereof, for the enhanced production of polymer nanocomposite materials due to dispersion and solvation of polymers and dispersion of inorganic nanoparticles in the Cyrene™ or ternary mixtures thereof.

More particularly, the invention relates to the use of Cyrene™ as herein described and ternary mixtures comprising Cyrene , water and the geminal-diol of Cyrene .

Background of the Invention

A solvent is a fluid substance, or mixture of fluid substances, that dissolves, or otherwise disperses, any other chemically distinct substance(s) [known as the solute(s)] to create a solution, dispersion or suspension. Additional benefits of solvents include mixing, viscosity modification, and temperature regulation. Applications of solvents include cleaning, extraction, and synthesis. An organic solvent is a solvent that is also an organic compound containing carbon atoms. The properties of solvent mixtures, including ternary mixtures, can be controlled by varying the ratio of the contributing components.

Switchable solvents are solvents that are normally chemically modified with carbon dioxide to reversibly change a hydrophobic amine solvent into a water miscible ammonium bicarbonate salt. ¹ Solvent mixtures of an amine and an alcohol also exhibit the same behaviour when treated with carbon dioxide. ² Switchable solvents are themselves a type of tuneable solvent, a class that includes supercritical fluids, near critical fluids, and gas expanded liquids. ³

Global consumption of solvents is significant, on the scale of tens of millions of metric tons per year, and is expected to increase. From an environmental and regulatory perspective, solvents cause issues relating especially to environmental pollution and human toxicity. The impact of solvent use can be reduced by (1) using less volatile or less toxic organic solvents and (2) using lesser volumes of solvent.

Cyrene™ is a bio-based solvent. A bio-based solvent is defined herein as one in which the carbon content originating from a bio-based source exceeds 25% w/w: ⁴ in the case of Cyrene™ the carbon content originating from a bio-based source is 100% w/w. Cyrene™ (dihydrolevoglucosenone or (l S,5R)-6,8-dioxabicyclo[3.2.1]octan-4- one) can be made in one step from levoglucosenone ((l S,5R)-6,8- dioxabicyclo [3.2.1 ]oct-2-en-4-one) .

Cyrene™ has the ability to interact with water to form a ternary mixture of water, Cyrene™, and the latter's geminal diol ((l S,5R)-6,8-dioxabicyclo[3.2.1]octan-4,4- diol), hereinafter referred to as "the geminal diol". The structure of Cyrene™ (left) and the geminal-diol form (right) are shown in Figure 1. When Cyrene™ is mixed with water the geminal diol of Cyrene™ forms instantaneously, in a proportion dependant, inter alia, upon the quantity of water present.

Dihydrolevoglucosenone (l S,5R)-6,8-dioxabicyclo[3.2.1]octan-4,4-diol (Cyrene™ germinal diol)

Figure 1

A geminal-diol (or gem-diol for short) is defined as any organic compound having two hydroxyl functional groups (-OH) chemically bonded to the same carbon atom.

Cyrene™ is regarded as a green solvent because it is not known to be toxic to humans, or damaging to the environment. ⁵ It is not considered to be a flammable liquid according to the requirements established by the Globally Harmonized System of Classification and Labelling of Chemicals (GHS). ⁶

A major application of solvents is the dispersion of different solid materials. A dispersion is a chemical system in which particles are separated throughout a continuous phase of a different composition (or state). There are three principle forms of dispersion: suspensions, colloids, and gels.

A suspension is a heterogeneous mixture containing solid particles that are sufficiently large for sedimentation. Usually they must be larger than one micrometre. Suspensions are unstable from a thermodynamic perspective. Colloids, in chemistry, are otherwise known as colloidal systems. The term is defined by IUPAC to imply that the molecules or polymolecular particles dispersed in a medium have, at least in one direction, a dimension that is roughly between 1 nm and 1 μπι, or that, in a system, discontinuities are found at distances of that order. Hence, a colloidal system is a mixture in which one substance of microscopically dispersed insoluble particles is suspended throughout another fluid substance. To qualify as a colloid, the mixture must be stable, or otherwise take a very long time to show appreciable settling. Colloids have a wide industrial use, and are used in applications such as paints, the food industry, inks, water treatment etc. One of the most important types of colloidal dispersions is gels and sols.

A gel is defined as a three-dimensional polymer network swollen by large amounts of solvent. Gels have found use in areas such as thickening agents in foods and personal care products, to cushioning agents, as well as in polymer chemistry.

A sol is a colloidal suspension of very small solid particles in a continuous liquid medium. Sols are quite stable and show the Tyndall effect. Examples include blood, pigmented ink, cell fluids and paint. Artificial sols may be prepared by dispersion or condensation.

In some applications it is advantageous to combine a gel and a sol in one state, such as, for polymer nanocomposites where the nanoparticles (prepared as a sol dispersion) need to be well integrated and spread uniformly within the polymer matrix (prepared as a gel), using a single solvent system or processing step.

The polymer industry is expected to grow with a Compound Annual Growth Rate (CAGR) of 3.9% over 2015-2020. The demand for polymers is driven by growth in end use markets, such as packaging, automotive, infrastructure, transport and telecommunication mainly from emerging economies. Polymers are continually being employed as substitutes for traditional materials such as metals, glass, paper, and other traditional materials in various applications due to its light weight and strength and the design flexibility polymers offer brand owners along with low-cost. This polymer industry sector can be divided into both thermoplastic and thermosetting plastics, where the incorporation of nanoparticles is a well-established strategy to extend polymeric materials applications and usage. The bio-polymer market has grown rapidly over the last few decades and is predicted to continue to increase due to the circular economy and the need for non-resource limited commodities. However, these bio-polymers have a number of deficiencies. They typically exhibit lower thermal stability and poorer mechanical properties than is desirable; and their low resistance to environmental conditions can limit their wider appeal. The synthesis of nanocomposites is a viable strategy to reduce the limitations of bio-polymers, whilst retaining their green characteristics.

The most abundant bio-polymer is cellulose, which is an attractive basis for the development of nanocomposites. ⁷ However, it is very difficult to dissolve cellulose in common solvents due to its highly extended hydrogen bonded structure. ⁸ In fact, the major problem when preparing cellulose hydrogels, for further processing of cellulose, is the lack of appropriate solvents that operate under sufficiently mild conditions. Conventional methods of dissolving cellulose require harsh conditions, with the following negative issues: low availability, toxicity, corrosivity, or volatility, which all make use and recovery challenging or impractical. ⁹ A solvent system of lithium chloride dissolved in N,N-dimethyl acetamide is known, but the latter is a reprotoxic solvent. ¹⁰

Recently, new developments with solvents such as N-methylmorpholine-N-oxide ( MMO), ¹¹ various ionic liquids (ILs), ¹² and alkali/urea (or thiourea) aqueous systems, ¹³ have also been shown to dissolve cellulose and/or to form a gel with cellulose.

Xylan is a dominant hemicellulose component found in plants and in some algae. Xylan makes up about 10-15% w/w of softwoods, about 10-35% w/w of hardwoods and about 35-40% w/w of the total mass in the residues of annual plants, such as oat hulls or spelts. The structure of xylan is more complex than that of cellulose, and has been summarised in several reviews. Xylan is actually a group of hemicelluloses that are found in plant cell walls and some algae. Xylans are polysaccharides made from units of xylose (a pentose sugar). Xylans are almost as ubiquitous as cellulose in plant cell walls and contain predominantly β-D-xylose units linked as in cellulose.

A simplified structure of hemicellulose in annual plants is shown in Figure 2.

Figure 2 A typical procedure for making a xylan (hemicellulose) gel requires harsh processing conditions, with a minimum of 5% w/w, of sodium hydroxide solution and temperatures around 80°C. ¹⁴ The use of salts in a dissolving medium inevitably leads to surplus waste, which is intensified by the need to neutralise the caustic solution first.

Chitin is a long-chain polymer of an N-acetylglucosamine, a derivative of glucose, and is found in many places throughout the natural world. It is a characteristic component of the cell walls of fungi, the exoskeletons of arthropods, such as crustaceans (e.g. crabs, lobsters and shrimps) and insects, the radulae of molluscs; and the beaks and internal shells of cephalopods, including squid and octopuses; and on the scales and other soft tissues of fish and lissamphibians. The structure of chitin is comparable to the polysaccharide cellulose, forming crystalline nanofibrils or whiskers. In terms of function, it may be compared to the protein keratin. Chitin has proved versatile for several medicinal, industrial and biotechnological purposes. Chitin is often converted to chitosan by N-deacetylation with alkali. ¹⁵ Chitin gels can be obtained in dilute acetic acid or by acylation of chitosan with various anhydrides in aqueous alcoholic acetic acid solutions. ¹⁶ Further, neutralisation of acetic acid produces waste materials therefore increasing the product cost. Chitin is known to be very difficult to dissolve.

The nano material known as graphene has generated substantial interest in recent years due to its unique mechanical, electrical, thermal and optical properties, ¹⁷ making it an interesting material for a vast number of varied applications, including nanocomposites with polymers and bio-polymers. ¹⁸

Liquid phase exfoliation methods for producing nanosheets, such as graphene, are cheap, versatile and simple to execute, and thereforescalable. ¹⁹ ' ²⁰ However, one of the limiting issues is that yields (weight of nanomaterial per volume of solvent) can be low, ²¹ and strategies to increase yield usually compromise quality. ²² Another problem with liquid phase exfoliation and dispersion (relevant to sonication and shear methods) is that the preferred solvents pose quite severe health risks. For the liquid phase exfoliation of graphite, the graphene dispersion is typically formed in reproductive toxicants (reprotoxics) such as N-methyl-2-pyrrolidone ( MP) and

23 24 25

dimethylformamide (DMF). ' ' Both solvents been placed on the candidate list of "Substances of Very High Concern" (SVHC), which is a prerequisite step to any substance becoming restricted and subject to authorization under the European REACH regulation (Regulation (EC) No. 1907/2006) before use or import into Europe is permitted. ²⁶ Safer solvent systems can be used, but the amount of graphene obtained in dispersion is significantly reduced, ²⁷ or these still require the graphene to be transferred from a suspension in NMP. ²⁸ Summary of the invention

We have now found that Cyrene™ mixed with water forms a ternary mixture in equilibrium with the geminal diol. Hereinafter reference to "geminal diol" shall be understood to mean the geminal diol formed from Cyrene™ in water. This effect has

29 30 31

been described on three occasions in the older literature, ' ' but no reference has ever been made to the existence of a ternary mixture of Cyrene™, the geminal diol and water. This ternary mixture (see Table 1 herein) may advantageously act as a solvent for making polymer gels/ solutions, nanoparticle sols and their homogeneous combination to produce nano-composite materials. The invention relates to the use of the sustainable solvent, Cyrene™ and mixtures of Cyrene™, the geminal diol and water; and their application for the dispersion of nanoparticles, bio-polymers and, subsequently, for the production of composites.

Thus, according to a first aspect of the invention there is provided a nanocomposite material comprising a dispersed phase and a continuous phase wherein the continuous phase comprises Cyrene™.

Cyrene™ is aprotic, meaning it is unable to act as a Bransted acid. However, the geminal diol is protogenic, meaning it is a proton donor and it is a Bransted acid. In the presence of water, Cyrene™ and the geminal diol are in a dynamic equilibrium that is very sensitive to its surroundings. This surprising feature allows the solvent system to adapt to stabilize materials with contrasting properties. Therefore the invention relates to a new tuneable solvent or dispersed phase system that is created under mild conditions (meaning ambient temperature, ambient atmosphere and ambient pressure).

Thus, in one aspect of the invention, the continuous phase may consist of Cyrene™. In another aspect of the invention the continuous phase may comprise a ternary system consisting of combinations of Cyrene™ (>0% w/w) in water (<100% w/w) and the resulting geminal diol (>0% w/w). Furthermore, the ternary system may be varied depending, inter alia, upon the nature of the dispersed phase. Table 1 herein refers (first column) to how much Cyrene™ (wt%) was added to water; the 3 ^rd and 4 ^th columns show respectively how much (mols) geminal diol is formed and how much (mols) water is left when normalizing to 1 mol of Cyrene™. Essentially the 3 ^rd and 4 ^th columns of Table 1 herein illustrate respectively the molar ratio of geminal diol: Cyrene™ and the molar ratio of water: Cyrene™ that results from adding a given amount of Cyrene™ (wt%) to water. Thus, in one embodiment the molar ratio of geminal diol: Cyrene™ may be from about 1 :0.1 to about 1 : 10; or from about 1 :0.5 to about 1 :9; or from about 1 : 1 to about 1 :8; or from about 1 :2 to about 1 :7; or from about 1 :3 to about 1 :6; or from about 1 :4 to about 1 :5. In another embodiment the ratio of water: Cyrene™ may be from about 1 :0.3 to about 1 : 1,000, by weight; or from about 1 : 1 to about 1 :500; or from about 1 :2 to about 1 :400; or from about 1 :5 to about 1 :300; or from about 1 : 10 to about 1 :200; or from about 1 :50 to about 1 : 100. In a particular embodiment of the invention, the ternary system may comprise from about 25% w/w to about 50% w/w water and from about 75% w/w to about 50% w/w Cyrene™.

It will be understood that in the ternary mixture described herein the amount of the geminal diol is unspecified as it is formed in equilibrium from the Cyrene™. It will also be understood that the ternary system may be varied depending, inter alia, upon the desired use of the continuous phase, e.g. to form a gel, solution or sol.

Thus, the dispersed phase may be a polymer or may be an inorganic material. The inorganic material may be a carbon based material, such as a carbon based nanoparticle or a non-carbon based inorganic material, e.g. a 2D metal dichalgogenide, particularly a transition metal dichalgogenide (TMDC), a boron nitride, etc. When the dispersed phase is a polymer it may be a synthetic polymer, for example, poly(vinyl alcohol) (PVA) or poly(ethylene oxide) (PEO); and mixtures thereof. Alternatively, the polymer may be a bio-polymer, including mixtures of bio-polymers. Bio-polymers may include, for example, chitin, hemicelluloses, cellulose, synthetic bio-based polymers such as polylactides (e.g. PLA), polyhydroxyalkanoates (e.g. PHB), etc. Desirably the polymer may form a gel.

When the dispersed phase is a carbon based material it may comprise a product of graphite, exfoliated graphite, carbon nanotubes and nanofibres, fullerenes, etc. Exfoliated graphite may comprise graphite flakes, nanoparticles of graphene, functionalised graphene, graphene oxide, partially reduced graphene oxide; and mixtures thereof. When the dispersed phase is a product of exfoliated graphite it may desirably be in the form of a gel or sol.

In a particular aspect of the invention nanocomposite material is produced in the form of a film, such as a bio-polymer film or a synthetic polymer film or a graphene film.

In another aspect of the invention nanocomposite material is produced in the form of a film, comprising a composite of a polymer e.g. a bio-polymer and carbon nanotubes. Thus, according to a further aspect of the invention there is provided a method producing a polymer film or a graphene film or a composite film as herein described, wherein said method comprises forming a dispersion of a polymer and/or a graphene in a ternary system as herein described; and evaporating the continuous phase. According to this aspect of the invention the film may be formed by pouring the dispersion onto a fluoropolymer film, e.g. a PTFE film. In addition, according to this aspect of the invention the film may comprise a bilayer film.

According to a further aspect of the invention there is provided the use of Cyrene™ as a continuous phase for producing a nano-composite material as herein described.

The use according to this aspect of the invention may comprise the use of a ternary system as a continuous phase, said continuous phase consisting of combinations of Cyrene™ in water and the resulting geminal diol.

The manufacture of nanocomposite materials is commonly achieved through wet impregnation techniques. To do so, a continuous phase is required to create a colloidal solution of the nanomaterial, that is added to a macromolecular gel and the continuous phase later removed.

One aspect of the invention is the dispersion of polymers, specifically bio-polymers to make a stable gel, in a continuous phase system consisting of combinations of Cyrene™ (>0%) in water (<100%) and the resulting geminal diol of Cyrene™ (>0%) to create a ternary system. Another aspect of the invention is the combination of a polymer matrix in solid, molten, gel, solution form etc., where the polymer is non-bio-derived etc. and the continuous phase system consists of combinations of Cyrene™ (>0%) in water (<100%) and the resulting geminal diol of Cyrene™ (>0%) to create a ternary system, added to a nanomaterial sol, where the nanomaterial is produced by graphite exfoliation to give monolayer graphene, few-layer graphene, multi-layer graphene, graphite flakes, or mixtures thereof, or the nanomaterial consists of functionalized graphene, graphene oxide, partially reduced graphene oxide or other carbon nanomaterials (nanotubes, fullerenes) and the continuous phase is Cyrene™, or a continuous phase system consisting of combinations of Cyrene™ (>0%) in water (<100%) and the resulting geminal diol of Cyrene™ (>0%) to create a ternary system.

According to a further aspect of the invention there is provided the use of Cyrene™ as a continuous medium for producing a dispersion of a nano-composite material.

Another aspect of the invention is the combination of a polymer matrix in solid, molten, gel, solution form etc., where the polymer can be synthetic or bio-derived and the continuous phase system consists of combinations of Cyrene™ (>0%) in water (<100%) and the resulting geminal diol of Cyrene™ (>0%) to create a ternary system, added to a nanomaterial sol, where the nanomaterial is produced by graphite exfoliation to give monolayer graphene, few-layer graphene, multi-layer graphene, graphite flakes, or mixtures thereof, or the nanomaterial is functionalized graphene, graphene oxide, partially reduced graphene oxide or other carbon nanomaterials (nanotubes, fullerenes), and the continuous phase is Cyrene™, or a continuous phase system consisting of combinations of Cyrene™ (>0%) in water (<100%) and the resulting geminal diol of Cyrene™ (>0%) to create a ternary system.

Another aspect of the invention is the combination of a bio-polymer gel, where the bio-polymer is cellulose, hemicellulose, alginic acid, polysaccharides, chitin, chitosan, chitosan derivatives, keratin from wool or polyvinyl alcohol; and the continuous phase system consists of combinations of Cyrene™ (>0%) in water (<100%) and the resulting geminal diol of Cyrene™ (>0%) to create a ternary system, added to a nanomaterial sol, where the nanomaterial is produced by graphite exfoliation to give monolayer graphene, few-layer graphene, multi-layer graphene, graphite flakes, or mixtures thereof, or the nanomaterial is functionalized graphene, graphene oxide, partially reduced graphene oxide or other carbon nanomaterials (nanotubes, fullerenes), and the continuous phase is Cyrene™, or a continuous phase system consisting of combinations of Cyrene™ (>0%) in water (<100%) and the resulting geminal diol of Cyrene™ (>0%) to create a ternary system.

In another aspect of the invention, the aforementioned combinations of polymer / bio- polymer solid, melt, gel, solution and nanomaterial sol are dried by removing the continuous phase to produce nanocomposite materials.

The invention creates nanocomposite materials that are characterized by a process where the continuous phase system consists of common components (Cyrene™ or the ternary system described herein) for both the bio-polymer and the nanomaterial, and the properties of the nanocomposites are linked to the processing method. The amount of residual Cyrene™ in the system may depend upon, inter alia, the strength of the vacuum, the number of freeze drying or evaporation cycles, the nature of the disperse material, etc. Generally, the nanomaterials may be characterized by a residual Cyrene™ value of from about 0% to about 5% by weight of the total material.

According to a further aspect of the invention there is provided a method of preparing a nanocomposite material which comprises:

• preparing a dispersion comprising a dispersed phase and a continuous phase wherein the continuous phase comprises Cyrene™; and · evaporating the continuous phase.

According to this aspect of the invention there is also provided a film prepared according to the method herein described. Detailed description of the invention

The addition of water to Cyrene™ instantaneously creates a reproducible proportion of geminal diol, decided by the ratio of Cyrene™ to water present. Figure 3a shows the ¹³ C NMR spectrum of neat Cyrene™ while Figure 3b shows the ¹³ C NMR spectrum of 10 wt% Cyrene™ in D ₂ 0 displaying predominately the six unique peaks for the Cyrene™ geminal diol. Figure 3c) shows a 1H NMR of 65% w/w Cyrene™ in D ₂ 0 showing the presence of both Cyrene™ and the geminal diol, the ratio of Cyrene™: geminal diol: D ₂ 0 is 1 : 2.29: 9.05. The 1H NMR determines the molar ratio of gem diol to Cyrene™ by setting the area under the Cyrene™ peak to 1 and recording the area under the gem diol peak. The amount of residual water then needs to be calculated: one knows how much water is initially present and one can subtract the amount of gem diol (= water used) from it.

As also shown in Figure 4 (based on NMR data), the addition of 20% w/w Cyrene by weight in water creates the largest proportion of geminal diol, more than ten times the amount of remaining Cyrene™. Cyrene™ molecules become more populous than the geminal diol only when water content is below 25% w/w.

Table 1*

: wt% cyrene ; Cyrene Geminal Diol ; Free H20

93.99 1.00 0.14 0.38

90.44 l.oo; 0.26; 0.69;

85.26 l.OOi 0.45; I.33;

80.19 1.00 0.74 2.32

74.30 l.oo; 1.151 4. I4;

69.77 1.00 1.64 6.49

65.24 1.00 2.24 10.04

59.41 l.oo; 3.36; 17.83;

55.08 l.oo; 4.34; 26.63;

50.15 1.00 5.57 40.88

44.86 l.oo; 6.73; 60.85;

40.00 l.oo; 8.Ο9; 88.90;

35.26 1.00 8.95 121.00

30.03 l.oo; 9.49; 164.36;

25.20 l.oo; 9.5i; 212.36;

20.21 1.00 10.06 300.40

15.38 1.00 8.90 378.61

10.17 l.oo; 8.82; 608.20;

5.02 l.oo; 5.97; 931.03;

* Amounts of H ₂ 0 and the Cyrene geminal diol normalized to 1 mol of Cyrene for different initial amounts of Cyrene™ in H ₂ 0 (in wt % Cyrene™ in H ₂ 0) (all percentages are w/w and were derived from 1H NMR measurements). Table 1 is illustrated graphically in Figure 4 herein. In Table 1 herein, column 1 is a percentage so the numerical value weight for weight percentage. The values in columns 2, 3 and 4 are molar quantities. Cyrene™ is conveniently set to 1 in the 1H MR, the amount of geminal diol is recorded from the 1H NMR and free H ₂ 0 is calculated.

The invention will now be described by way of example only and with reference to the accompanying figures in which:

Figure 3a) is a ¹³ C NMR spectrum of neat Cyrene™;

Figure 3b) is a ¹³ C NMR spectrum of 10 wt% Cyrene™ in D ₂ 0 showing predominately the characteristic peaks of the Cyrene™ geminal diol;

Figure 3c) is a 1H NMR spectrum of 65 wt% Cyrene™ in D ₂ 0 exemplifying the presence of both Cyrene™ and the geminal diol;

Figure 4 illustrates the amounts of H ₂ 0 and the Cyrene™ geminal diol (in mol) normalized to 1 mol of Cyrene™ for different initial amounts of Cyrene™ in H ₂ 0 (in wt % Cyrene™ in H ₂ 0) (data from Table 1 );

Figure 5 is a typical Raman (514nm) spectrum of graphene cast from a dispersion (sol) in Cyrene™;

Figures 6 a) - c) illustrate the a) change in concentration of dispersed graphene in Cyrene™ with different starting graphite concentration after 15 mins of sonication; b) the change in concentration of dispersed graphene in Cyrene™ (starting graphite concentration, 1.5mg/ml) with different sonication times, and; c) the change in the A _D /AG ratio of dispersed graphene in Cyrene™ (starting graphite concentration, 1.5mg/ml) with different sonication times; Figure 7a) illustrates the dispersion of graphene in Cyrene™ after 15 mins sonication; figure 7b) illustrates dispersions of Cyrene™-graphene after various sonication times, and after one month illustrating the dispersions stability;

Figure 8 illustrates the yellowing of Cyrene™ in the presence of graphite;

Figures 9 a-c) illustrates the formation of a gel;

Figure 10a) illustrates poly-L-lactide (PLLA) and polymer composite dispersions in a Teflon® mold;

Figure 10b) illustrates PLLA nanocomposite film with well dispersed graphene;

Figure 10c) is a scanning electron microscopy image of the PLLA-graphene composite, two graphene flakes are indicated in dashed circles; they are well dispersed with a size of 580 nm {bottom left-hand corner) and 430 nm {top right-hand corner) respectively;

Figure lOd) is a scanning electron microscopy image of the PLLA-graphene composite, two smaller graphene flakes {as previously shown in Figure 10c)) are visible, as is one larger flake with a size of 3.31 μπι, a hole is evident where a graphene flake has been pulled out during fracture with a size of 2.17 μπι;

Figure lOe) illustrates PFIB and polymer composite dispersions in a Teflon® mold;

Figure lOf) illustrates poly-[(R)-3-hydroxy-butyrate] (PFIB) films showing some agglomeration of the graphene;

Figure lOg) are pictures of the bilayer PHB/graphene composite, images: edge on

{left) and lying flat {right), a schematic of the construction of the composite is also provided {centre); and

Figure lOh) is a scanning electron microscopy image of the PFIB/graphene bilayer composite. Examples

Example 1

General method of making nanomaterial dispersions (full range of % wt. Cyrene™)

Nanoparticles created by the exfoliation of graphite in Cyrene™ (containing 1-3 mg of graphene in 1 ml of continuous phase) were generated as a dispersion by applying ultrasound treatment during variable time from 2 to 20 minutes to a mixture of graphite and a continuous phase, followed by 10 minutes of centrifugation at 7000 rpm. The graphene sol consists of nanoparticle flakes with thickness ranging from monolayer to few layers of graphene.

The time range chosen is known to be sufficient to aid graphene-continuous phase dispersion, but also low enough to limit reductions in nanoparticle size and defects, and continuous phase degradation and subsequent formation of oligomers or polymers that can then adhere or radically graft to the nanoparticle surface, further stabilizing them in solution. ³² ' ³³

The concentration of dispersed graphene in the supernatant was then measured using UV spectroscopy in accordance with established methods as defined by Coleman et

The graphene dispersions were visually checked and are found to be stable over several weeks. Example 2

General method of making bio-polymer gel (full range of %Cyrene™)

A mixture of Cyrene™, the geminal diol and water is created by the addition of water (<100%) to Cyrene (>0%), in any ratio. 0.01-0.2 grams of bio-polymer were mixed at room temperature with 2-4 millilitres of the prepared continuous phase mixture under intense agitation during 24-96 hours. Afterwards the mixture was left a duration from 4-96 hours at room temperature.

The gel quality of the obtained suspensions was estimated using a standard transparency test and a pour point test.

Example 3

General method of combining sol and gel to prepare nanocomposite precursors

Sol of graphene and gel solution of bio-polymer obtained by the above described methods are combined at room temperature under very intense agitation. Final nanoparticle loading is controlled by the sol-gel ratio, where a highly concentrated sol produces a higher nanoparticle loading in the final nanocomposites.

Example 4

Preparation of highly concentrated graphene dispersion

Cyrene was added (3 mL) to a vial containing 4.5 mg of graphite (Aldrich, <45 micron, 99.99%, B.N. 496596-113.4G). The mixture was treated with an ultrasonic probe during 15 minutes and the dispersions were centrifuged at 7000 rpm for 10 minutes. The supernatant was isolated by pipette. The concentration of the graphene dispersion was 0.24 mg-ml ^"1 . Increasing sonication time to 120 min, the final dispersion concentration was 0.70 mg-ml ^"1 . Using an initial graphite concentration of 10 mg-ml ^"1 with 15 min sonication, the concentration of the graphene dispersion reached 0.99 mg-ml ^"1 . In all cases the dispersion showed good stability, over several weeks.

Example 5

Preparation of a time stable graphene sol

10 mg graphite (Aldrich, <45 micron, 99.99%, B.N. 496596-113.4G) was dispersed in 2 mL water/ 2 mL 25 wt% Cyrene™ in water/ 2 mL 50 wt% Cyrene™ in water / 2 mL 75 wt% Cyrene™ in water / 2 mL pure Cyrene™. All solvent combinations were stirred prior to the addition of the graphite. The resulting graphite dispersions were stirred for 48h and the dispersion rested.

10 mg of graphite (Aldrich, <45 micron, 99.99%, B.N. 496596-113.4G) was added to a vial containing Cyrene™ (75% of total liquid) and water (25% of total liquid). The mixture was stirred for 48 hours and the dispersion rested.

Example 6

Preparation of cellulose gel

200 mg microcrystalline cellulose powder [20 μπι Aldrich catalogue number: 31-069- 7] was dispersed in 2 mL water/ 2 mL 25 wt% Cyrene™ in water/ 2 mL 50 wt% Cyrene™ in water / 2 mL 75 wt% Cyrene™ in water / 2 mL pure Cyrene™. All solvent combinations were stirred prior to the addition of the cellulose. The resulting cellulose dispersions were stirred for 48h and the dispersion rested. An improved dispersion was achieved with water, 75% Cyrene™ compared to the dispersion with pure Cyrene™.

Example 7

Preparation of hemicellulose gel

200 mg hemicellulose (Xylan from beechwood, Sigma Aldrich, Catalogue number X4252-100G) was dispersed in 2 mL water/ 2 mL 25 wt% Cyrene™ in water/ 2 mL 50 wt% Cyrene™ in water / 2 mL 75 wt% Cyrene™ in water / 2 mL pure Cyrene™. All solvent combinations were stirred prior to the addition of the hemicellulose. The resulting hemicellulose dispersions were stirred for 48h and the dispersion rested. Again, an improved dispersion was achieved with water present.

Example 8

Preparation of chitin gel

50 mg chitin [from crab shells, Sigma Aldrich, catalogue number C-7170 (100g)] was dispersed in 2 mL water/ 2 mL 25 wt% Cyrene™ in water/ 2 mL 50 wt% Cyrene™ in water / 2 mL 75 wt% Cyrene™ in water / 2 mL pure Cyrene™. All solvent combinations were stirred prior to the addition of the chitin. The resulting chitin dispersions were stirred for 48h and the dispersion rested. Again, an improved dispersion was achieved with water present.

Example 9

Preparation of a bulk nanocomposite of graphene and PLLA

The bio-polymer poly-L-lactide (PLLA) was dissolved in Cyrene™ at a concentration of 98 mg per 3 mL under stirring conditions at a temperature of 120 °C, after which a further 4.15 mL of Cyrene™ was added and the mixture left stirring for a further 30 minutes. Then graphene dispersed in Cyrene™ was added (4.15 mL, equivalent to approximately 2 mg of dispersed graphene), to produce a PLLA-graphene composite at approximately 1 wt% loading of nanoparticle. The mixture was then poured into Teflon® moulds (see Figure 10a)). Once prepared the samples were placed in a vacuum oven set at 120 °C for 24 hours to ensure complete removal of the continuous phase.

The PLLA composite showed no visible sign of nanoparticle agglomeration which was further verified with SEM (see Figure 10c) and Figure 10d)).

From the SEM analysis of the PLLA/graphene nanocomposite (Figure 10d)) it can be seen that the graphene flakes are well dispersed and not agglomerated, with flake sizes ranging from 430 nm to 3.31 μπι. Overall it can be seen that the preparation of biopolymer composites using the bio-derived continuous phase Cyrene™ as a dispersing agent for graphene (and to solubilise the polymer) can be achieved efficiently and without the need of other continuous phases, thus minimising the environmental impact during the preparation stage. There is potential at larger scales for continuous phase recovery, but this was not pursued at this stage.

Example 10

Preparation of a bulk nanocomposite of graphene and PHB

The bio-polymer PHB was dissolved in Cyrene™ at a concentration of 98 mg per 3 mL under stirring conditions at a temperature of 120 °C, after which a further 4.15 mL of Cyrene™ was added and the mixture left stirring for a further 30 minutes. Then graphene dispersed in Cyrene™ was added (4.15 mL, equivalent to approximately 2 mg of dispersed graphene), to produce a PHB-graphene composite at approximately 1 wt% loading of nanoparticle. The mixture was then poured into Teflon® moulds (see Figure 10e)). Once prepared the samples were placed in a vacuum oven set at 120 °C for 24 hours to ensure complete removal of the continuous phase.

It was found whilst preparing the films that for the PFIB composite some agglomeration of the graphene was present in the final film as shown in Figure lOf. Improvements were found when the amount of continuous phase used was reduced, significantly increasing the viscosity of the medium, and hence preventing self- association of the prepared dispersed graphene nanomaterial. Example 11

Preparation of a bilayer nanocomposite material of graphene and PHB

The bio-polymer PHB was dissolved in Cyrene™ at a concentration of 196 mg per 6 mL of continuous phase under stirring conditions at a temperature of 120 °C. A graphene dispersion was prepared but was not centrifuged to maximise the quantity of dispersed graphene/graphite present (5 ml). This was then deposited on a 0.2 μιη Fluoropore™ membrane during suction to leave behind a graphene/graphite film on the membrane. Afterwards, the polymer solution was poured on top and left to cool, creating a bilayer film. The sample on the membrane was then placed in a vacuum oven at 120 °C for 24 hours to remove any residual continuous phase still present.

The DC-conductivity value of the prepared non-centrifuged graphene layer (~ 84% graphitic, 16% graphene) of the composite was >2.1 S cm ^"1 . This use demonstrates potential for another application of the use of highly concentrated Cyrene™-graphene dispersions in non-toxic based applications.

The PFIB/graphene bilayer is shown in Figure lOg), where the central schematic provides exact information on its construction. SEM images (Figure 10h)) were obtained, and show that the polymer (brighter region) and graphene/graphite layers (darker region, bottom image) are in intermittent contact at the interfacial region, yet sufficient to signify good compatibility and bonding, important for potential application in sensor appliances etc.

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