The present invention also relates to a method for manufacturing a fiber comprising at least one self-organized polymer, with the method comprising the following steps: Preparing a spinning solution comprising at least one organic solvent and at least one self-organized polymer, and spinning the self-organized polymer into the fiber by an electrostatic spinning method in such a manner that the spinning solution is fed through a capillary having a first potential towards a receiving area having a second potential.

The present invention also relates to a fibrous structure, which has free space between fibers forming a network.

In some technical fields, such as filtration, in which fibers are used there has in recent years been an attempt to find a way to produce fibrous products having a high surface area compared to their weight, e. g. >200 m2/g. Nano-scale fibers (diameter at the most ca. 1 micron) are one useful solution. However, from a practical viewpoint, the nano- scale fibers are difficult to manufacture and further process because of their small dimensions.

Besides the nano-scale fibers, certain polymer concepts lead to controlled nanostructures. Self-organization leads to well defined nanostructures due to competing interactions (M. Muthukumar, C. K.

Ober, and E. L. Thomas, Competing Interactions and Levels of Ordering in Self-Organizing Polymeric Materials, Science, 1997.277 : p. 1225). A well-known example in the prior art is based on block copolymers where mutually repulsive polymeric blocks are covalently connected within the same polymer chain (I. W. Hamley, The physics

of block copolymers, 1998, Oxford University Press). In diblock copolymers, eg. lamella, cylindrical, or spherical self-assembled nanodomains are obtained of the sizes of ca. 1-150 nm and more complicated structures are rendered when more blocks are used, such as triblock, tetrablock, pentablock and the like. The structures in bulk or films have amply been described in the said prior art. By contrast, there have been few efforts to prepare nanoscale fibers of less than ca. 1 micron diameter using self-assembling block copolymers. Styrene- butadiene-styrene triblock copolymer has been electrospun to render <BR> <BR> nano-scale fibers (Fong and Reneker, J. Polym. Sci. , Polym. Phys. Ed., 1999,37 : p. 3488.) Nanoporous materials in bulk or film phase have been prepared e. g. by self-organizing block copolymer with a block, which can be degraded.

Well defined structures are achieved e. g. incorporating diblock copolymers, which consist self-organized polystyrene, and polymethyl methacrylate domains where the latter domains are afterwards degraded using UV-radiation (see eg. T. Thurn-Albrecht, J. Schotter, G. A. Castle, N. Emley, T. Shibauchi, L. Krusin-Elbaum, K. Guarini, C. T.

Black, M. T. Tuominen, T. P. Russell : Ultrahigh-density Nanowire Arrays Grown in Self-Assembled Copolymer Templates, Science, 2000,290 : p. 2126). It would be desirable to combine porosity due to self- organization and nano-scale fibers, to further increase the surface area and combine with functionalities. However, no concept is described to render nanoporous nano-scale fibers based on block copolymers and selective emptying, removal or degradation of one or more self- organized domains within the fibers.

Another concept to achieve porous materials in bulk or films is based on sol-gel process of block copolymers and inorganic materials where the block copolymer serves as a template for self-organized nanostructures for the inorganic material and nanostructured ceramic material is rendered. By heat treatments, nanoporous materials in bulk or films have been described (P. F. W. Simon, R. Ulrich, H. W. Spiess, U.

Wiesner: Block Copolymer-Ceramic Hybrid Materials from Organically <BR> <BR> Modified Ceramic Precursors, Chem. Mater. , 2001,13 : p. 3464).

Importantly, no concept to prepare nano-scale porous fibers has been disclosed based on such methods.

Still another concept to render self-organized materials is based on using mutually repulsive oligomeric or polymeric constituents, which are physically bonded together by complementary physical interactions, such as hydrogen bonds, coordination, proton transfer and the like. Use of such interaction has been described (J. -M. Lehn, Supramolecular Chemistry, 1995, Weinheim, VCH). In the prior art, diblock copolymers are used where amphiphilic oligomers are physically bonded within one block by hydrogen bonding, coordination, or proton transfer thus leading to structural self-organizational hierarchy (O. Ikkala, G. ten Brinke : Functional Materials based on Self- Assembly of Polymeric Supramolecules, Science, 2002,295 : p. 2407) Polystyrene-block-poly (4-vinylpyridine) has been used in combination with the amphiphilic pentadecylphenol which forms self-organizing hydrogen bonded complexes with poly (4-vinylpyridine) or zinc dodecylbenzene sulfonate which forms self-organizing coordinated complexes with poly (4-vinylpyridine). The amphiphile can be removed or cleaved afterwards from the structure by solvent treatment, dialysis, thermal treatment or the like, thus leaving open porous framework with cylindrical or sheet-like cavities or voids, whose typical dimensions are ca. 1nm-150nm, depending on the molecular weights of the used polymers (R. Mäki-Ontto, K. de Moel, W. de Odorico, J. Ruokolainen, M. Stamm, G. ten Brinke, and O. Ikkala,"Hairy Tubes" : Mesoporous Materials Containing Hollow Self-Organized Cylinders with Polymer Brushes at the Walls. Adv. Mat. , 2001.13 : p. 117; Valkama, S. , T.

Ruotsalainen, H. Kosonen, J. Ruokolainen, M. Torkkeli, R. Serimaa, G. ten Brinke, and O. Ikkala, Structural Hierarchy Based on Block Copolymers Coordinated to Amphiphiles as a Template for Mesoporous Materials. Macromolecules, 2003.36 : p. 3986). The concepts in the prior art disclose methods for bulk or film samples but no concept to render nano-scale fibers has been described. In another modification, the length of the polystyrene block in polystyrene-block- poly (4-vinylpyridine) has been selected to be shorter which leads to polystyrene cylinders of diameter ca. 10 nm within the matrix consisting of poly (4-vinylpyridine) hydrogen bonded with pentadecylphenol (G.

Alberda van Ekenstein, E. Polushkin, H. Nijland, O. Ikkala, and G. ten Brinke, Shear Alignment at Two Length Scales: Comb-Shaped Supramolecules Self-Organized as Cylinders-within-Lamellar Hierarchy. Macromolecules, 2003.36 : p. 3684). Upon dialysing the pentadecylphenol off, individual polystyrene fibers with poly (4- vinylpyridine) corona are split from the original bulk (sic) material.

Importantly, no concept to use nano-scale fibers is disclosed.

A general concept to functionalize surfaces is to use so-called polymer brushes that can be grafted onto or grafted from the surface (see eg.

R. A. L Jones, Soft Condensed Matter. 2002, Oxford : Oxford University Press).

Fong & Reneker (H. Fong and D. H. Reneker, Elastomeric Nanofibers <BR> <BR> of Styrene-Butadiene-Styrene Triblock Copolymer. J. Polym. Sci. ,<BR> Polym. Phys. Ed. , 1999.37 : p. 3488) described electrostatic spinning of styrene-butadiene-styrene tri-block copolymers in order to prepare non-woven fabric. They observed anomalies on fiber surface, but they aimed to remove them by means of annealing, as the target was to prepare homogeneous elastomeric fiber material.

A generally known technology is to manufacture non-wovens using microfibers of sizes ca. 1-2 micron, thus rendering advantageous properties like facile cleaning, leather-like appearance, and high <BR> <BR> filtration capability. (Adnadur, S. , Handbook of Industrial Textiles, Technomic Publishing Company 1995). Combination of non-woven material with sub-micron fibers leads to superior properties, as a very large ratio between area to volume is achieved, thus improving their physical properties and chemical activity. As very high dielectric constant and high surface absorption can be achieved, the materials are useful e. g. in filter applications (Albrecht, W. et. al., Non-Woven Fabric, Wiley-VCH, 2003).

Melt blowing technology is a commonly used method for manufacturing very fine filaments of diameter of ca. 2 micrometers or greater. US Patent Application 6,481, 638 to Schulz discloses a method and a nozzle to produce fine powders based on molten material using gases.

Similarly, the Nanoval technology allows to manufacturing ca. 0.7-4 micrometer fibers based on ultrasonic melt blowing with cooled air (L.

Gerking, Chemical Fibers International 52 (2002) 6,424-426).

Electrostatic spinning allows manufacturing of polymeric nanofibers with diameters as low as ca. 50 nm (Doshi, J. , Reneker, D. H. , Journal of Electrostatics 1995,35, 151-60). This technique is used to produce filter materials where a thin layer of nanofibers is deposited on a substrate of spun-bond or melt-blown fabric. The product is useful through its large surface area and ability to collect static charges, thus improving dust removal in the filter. (International Fiber Journal February 2004, p. 48) The method and the apparatus for electrostatic spinning is claimed already early in the US Patent 1,975, 504 to Formhals. Continuous non- woven type web by means of electrostatic spinning is claimed in US Patent 4,143, 196 to Simms. Various improvements for the technology have been made since then, and a feasible process for manufacturing such nanofiber web coated products is disclosed recently e. g. in application WO 03 004735 to Hag-Yong Kim.

US Patent Application 6,183, 670 to Torobin et al. proposes a composite filtration medium web of fibers which contain a mixture of sub-micron and greater than sub-micron diameter polymer fiber. The filtration medium produces a single high velocity two-phase solids-gas jet of discontinuous fibers entrained in the air.

Microfiber webs are well known in various patents and publications, like US Patent 3,849, 241 to Butin et al., and Naval Research Laboratory Report 4364 by Wendt et al. Superfine microfiber non-woven web can be produced according to US Patent 5,935, 883 to Pike by means of extruded and melt blown bi-component fibers, where at least one component is hydrophilic to enable splitting into microfiber, which are typically higher than micron size.

Another approach to produce nanofiber is based on fibrillation linear cellular structured fiber such as cellulose into sub-fibers of fibrils with

nano-sized dimension. KX Industries has presented several articles on this subject where easily fibrillated Lyocell fibers were used to produce nanofibers but the fiber varies greatly in size and formation. Spunbond fabric from island-in-the-sea fibers has been delivered up to 360 islands in fiber, leading down to 500 nm unit fiber size. (International Fiber Journal February 2004, p. 48).

Controlled splitting of nanofibers from self-assembled or self-organized bulk material has been described by de Moel et al. in Chem. Mater., 2001,13, 4580-4583, and G. Alberda van Ekenstein et al. in Macromolecules 2003,36, 3684-3688.

In the following, problems related to the prior art are explained: The melt blowing method has not been successfully applied if several starting materials have to be used, such as in the bicomponent situation, to render truly nanofibers where the diameter would be in range of 5... 400 nm. Neither the fiber size is well controlled.

Electro-static spinning can be used as a coating process for a non- woven substrate but it has a limited production speed. Also the coating layer formed through electro-static spinning is mechanically weak and typically not well bonded to the non-woven substrate. A nonbonded nanofiber remaining during and after the manufacturing process may cause problems in work environment hygiene and in the final application.

A practical method for post process nano-scale fibers from self- organized polymers in industrial scale is missing.

The present invention solves the problems related to the existing technology.

The method for manufacturing a fibrous structure is characterized in that the material is split into finer structures after forming the fibrous pre-structure. The method solves problems by means of controlling the size of the formed sub-micron fibers to be released in the non-woven

structures and providing a simple manufacturing method to locate the sub-micron fibers in the non-woven structures.

The method for manufacturing ai fiber is characterized in that nano- domains in the fiber are controlled after the self-organized structure is formed. The method provides an industrially applicable manufacturing method for high surface area material through porous fibrous structures.

The fibrous structure of the invention is characterized in that the free space includes fibers formed of at least one self-organized polymer.

In the following, the method for manufacturing the fibrous structure is explained: The fibrous structure is typically woven, knitted, or non-woven material, preferably it is a non-woven. Non-woven structures are products manufactured typically of staple fibers by means of dry-laying, wet- laying, or mechanical carding processes. The non-woven materials are useful for several kinds of technical and clothing applications, such as filtration, hygienic, medical, composite, and protective clothing, among several other applications. The fibrous structure is a cloth material, which comprises fibers or fragments, which have a diameter of less than 400 nm, preferably less than 200 nm, but in certain cases it is possible to produce fibers and fragments having even a diameter which is between 5 and 50 nm. The fibrous structure comprises at least a portion of material, which include self-assembled nano-domains. The material including self-assembled nano-domains may be for example a fiber, a particle, a film, or a coating. Preferably the material including self-assembled nano-domains is a fiber. In this application, the term self-assembled is used as a synonym of the term self-organized.

The self-assembled nano-domains are formed so that blocks, which repel each other, are chemically connected together and in certain conditions they start to organize themselves. For example, when a spinning solution including self-assembling nano-domains is under a shear force the self-assembling starts.

The material including self-assembled nano-domains is first brought in or onto a fibrous pre-structure and then the material including self- assembled nano-domains is split in such a manner that finer structures are formed. The finer structures may be nano-scale fibers obtained from a fiber having a conventional diameter, or from a film, which is split. The nano-scale fibers have typically a diameter, which is less than 400 nm. Preferably the diameter is less than 200 nm. The finest fibers may have a diameter, which is between 5 and 50 nm.

The present invention is a practical method for manufacturing non- woven material comprising of a mixture of sub-micron and greater than sub-micron diameter polymer fibers, which form a useful structure that forms a macro web where porosity is formed due to distributed sub- micron or nanofiber material achieved by splitting nano-scale fibers of substructures from self-assembled templates. Furthermore, the invention discloses the process and suitable material useful for the web-product. In addition, the invention gives examples of such web- products, their materials and manufacturing.

In the preferred embodiment, a macro-sized filament comprises self- assembled or self-organized material, and split in a post-processing step into nanofibers or substructures, when the formed nanofibers or substructures remain attached and supported in product structure.

The macro-sized filament comprises self-assembled or self-organized material, which can be produced by means of electro-static spinning collecting one or more fibers in bundle. In the embodiment the self- assembling polymeric material is electro-statically spun with or without a supportive polymer from a separate spinneret on a drum and collected as a nano-filament yarn.

Alternatively the cladding layer can be produced by means of electro- static spinning. The self-assembling polymeric material is spun on a surface of a core, which can be a conventional fiber. In the embodiment the continuous filaments are drawn through electro-static field and coated thereby.

In the separate embodiment the self-assembling polymeric material is extruded in a form of fiber, or in a form of bicomponent fiber. In another embodiment, a macro-sized filament comprises self-assembled or self- organized surface layers that are split in a post-processing step into nanofibers or substructures, where the thus formed nanofibers or substructures do not remain attached to the supporting macrofiber after the splitting. In still another embodiment, a self-assembled or self- organized macro-sized filament is split in a post-processing step into nanofibers. A staple fiber, which is able to split, is produced and used to manufacture the nano-woven by means of dry-laying, wet-laying, mechanical carding or other suitable means, split after the manufacturing of the fabric. The splitting to nanofibers takes place after the actual manufacturing of the non-woven.

Finally the self-assembling polymeric material can be co-spinned out of same solution of a compatible polymer forming the actual supportive structure.

The monofilaments or yarns including self-assembled nano-domains are cut in the later process to staple fibers. The staple fibers are used for manufacturing of the non-woven. In the final manufacturing step the staple fibers are split by a suitable manner.

For manufacturing of the non-woven product can be used for example the wet laying technique which resembles the paper making process. A suspension comprising conventional fibers and material including self- assembled nano-domains is fed on a forming web. Water is removed through the forming web, and thus the fibrous pre-structure is formed.

The pre-structure is pressed, dried and bonded by a suitable method, such as bonding fibers or adhesive agents. The material comprising self-assembled nano-domains is split after the pre-structure is formed.

The splitting can take place concurrently with the drying process, or it can take place before or after the drying process but it is essential that the fibrous pre-structure is already formed before the splitting because the split structures must be entrapped by the pre-structure.

The material including self-assembled nano-domains may vary a lot.

Specific block copolymers can be used which contain degradable blocks, which allow post-processing with e. g. UV-radiation, reactive ioning etching, biological degradation or the like, to allow splitting of nanofibers or substructures therefrom. Typical degradable block is polymethylmethacrylate that can be degraded by ultraviolet radiation, certain unsaturated polymers, such as polybutadiene that can be reactive etched, or polylactic acid that can be biodegraded. Such processes render a situation that the polymer chains within certain nano-scale domains undergo controlled and selective scission into short length entities that leads to splitting of the essentially nondegraded nanoscale domains. In another embodiment, certain blocks of block copolymers have been swollen with oligomeric additives that are easily removable due to their low molecular weight, either by selective solvent treatment or vacuum treatment, thus causing splitting into nanofibers or substructures. The self-assembled polymers may vary widely, comprising functional groups such as ethers, esters, sulphonamides, amides, amines, acrylates, sulfonates, sulfonic acids, carboxylic acids, carboxylates, phosphates, and the like, such as polyethylenoxide, polyalkyethers with alkyl chain lengths from e. g. 1 to 20 methyl units, polyamides, polypeptides, aromatic polyamides, polyimides, polylactides, polyesters, polyethylene imines, polyurethanes, polyisocyanates, cellulosics, starch, chitosans, phenolics, conjugated polymer, polypeptides, or proteins. For example, a diblock polymer can be formed of polyethylenoxide in combination with polyamide, polystyrene, polyethylene, polypropylene ; or polystyrene with polymethylmethacrylate, polyacrylic acid or polylactide ; or polyamides with polyalkylethers. It is possible to increase the number of blocks, or incorporate different architectures.

Feasible block copolymers include also polyamide-polyalkyether segmented block elastomers (registered trademark PEBAX), polyester- block-polyethyleneoxide (registered trademark SYMPATEX), poly (styrene-d-butadiene) and poly (styrene-b-hydrogenated butadiene (ethylene propylene)) (registered trademark KRATON), segmented polyurethane elastomers, and polystyrene-block-polyacrylic acid. It is also anticipated that one or more additives, such as amphiphiles, surfactants, plasticizers, high boiling point oligomers, or

homopolymers are selectively bonded or swollen within one or more blocks of block copolymers to form an integral part of the self- assembled nanostructure within the fiber. The material self-assembles spontaneously and finally the additive, such as the amphiphile is cleaved off either by solvent extraction, dialysis, or thermal treatment.

For example, a polystyrene-block-poly (4-vinylpyridine) with the amphiphiles such as alkylphenols, or zinc dodecylbenzene sulphonates can be used.

The additives may vary widely, and must be selected by their bonding and swelling capability to the specific domains of the self-assembling materials where they form the integral part of the nanostuctures during the spinning process. Therefore their flashpoint has to be high enough to withstand the electrospinning. However, they must be separately removable after the spinning. Hydrogen bonding additives include substituted phenols, substituted di-or trihydroxybenzenes, substituted gallates, sulfonamides, surfactants such as aliphatic or aromatic alkyl sulfonates or alkyl sulfonic acids or phosphates or cationic or nonionic surfactants, polyglycolic compounds, such as glycerol, metal salts, and the like. Even low molecular weight homopolymers can be used to selectively bond to selected nano-domain and can be removed after the electrospinning.

The fibrous structure may include supporting fibers. They can vary widely from cellulosic, and modified fiber to man made fiber, not excluding mineral, metallic, or glass fiber. Also the processing can vary widely. Conventional spinning can be made by means of melt-spinning, wet-spinning or dry-spinning. Also electro-static spinning can be used.

The splittable fibers may include nanostructures, which are for example lamella or tubular. The splittable fiber can be micron or several microns thick, but after cleaving by means on chemical, irradiation, thermal, or other means it will split into nano-scale fibers or other finer structures.

The splittable fiber forming nanostructures can be collected on the macrofibers by means of introducing the macrofiber in the spinning

prosess of the splittable fiber. The macrofibers in the case are acting as a carrier for the splittable fiber.

Futher the nanostructured fibers based on self-assembled material can be bundled together. The yarns of nanostructured fibers are forming dimensions similar to the macrofiber in the application. The nanofiber yarns can be formed collecting product of several spinneret through a round orifice as a counter electrode. Alternatively the yarn can be collected on a rotating drum.

One possible alternative for manufacturing a nano-scale fiber is to use electrostatic spinning. The fibers which are produced by the electrostatic spinning method are usable in the method for manufacturing the fibrous structure. The method for manufacturing a nano-scale fiber comprises at least one self-organizing polymer with an internal nanostructure, where the said self-organized internal nanostructure within the fibers can be at least partially emptied by removing, cleaving, or degrading selectively at least one of the self- organized nanodomains, thus opening cavities or voids within the nanofibers, or splitting the said nanofibers into two or more distinct subfibers of even smaller diameters. It is also an object of the present invention that the self-organization within the nano-scale fibers comprises complementary physical interactions, such as hydrogen bonding acceptor-hydrogen bonding donor complexes, coordinative complexes, proton acceptor-proton donor complexes and the like. It is still an object of the present invention that the self-organized internal nanostructure within the nano-scale fibers comprising physical complementary interactions is partially emptied by removing, cleaving or degrading molecules selectively from at least one of the self- organized nanodomains within the fibers, thus opening cavities or voids within the said nanofibers, or splitting the said nanofibers into two or more distinct subfibers of even smaller diameters.

The method of the invention is a continuous process in which a fiber from a self-organized polymer can be manufactured rapidly and cost- effectively. Astonishingly a self-organized polymer is able to organize itself during a short period of time, typically 1/1000-1/10000 s, under

an influence of an electric field, which is formed between the capillary and the receiving area. It is possible that the self-organizing behavior starts in the spinning solution, continues in the capillary and finishes after the droplet has left the capillary. It is also possible that the self- organized is-not complete; There can be discontinuities in the structure.

The used electrospinning method has certain typical characteristics.

The strength of the required electric field is between 1 and 4 kV/cm, the diameter of the hole in the capillary is 0.5-3 mm, the distance between the tip of the capillary and the receiving area is between 100 and 1000 mm, and the voltage of the electrode pairs can be for example +95 kV/0 kV or +45 kV/-45 kV. Usually the voltage of the electrode is at the most 150 kV. The self-organized polymer organizes itself during processing in such a manner that when an electrically charged droplet of a spinning solution flows out of the capillary, the electric field between the capillary and the receiving area have an effect on the droplet, and the droplet stretches to a fiber and at the same time an organized structure is formed. Before stretching to a fiber the droplet becomes conical at the tip of the capillary ; This phenomenon is known as a Taylor cone. In order to increase the production capacity the capillary can be pressurized or subjected to centrifugal force.

The organized structure develops instantly after the droplet leaves the capillary ; It is observed that only approximately 25 mm is required for the organizing of the structure. However, the distance between the capillary and the receiving area shall be longer than the mentioned 25 mm because the solvent must evaporate from the fiber at least partially before the fiber reaches the receiving area. The evaporation speed of the solvent can be adjusted by changing pressure or gas surrounding the fiber during drawing. A normal pressure, a vacuum, a partial vacuum, or an elevated pressure are possible pressure variations. The gas can be for example air or nitrogen. It is possible that some drying means is required. In addition to the above-mentioned, it is possible that the self-organizing behavior already starts in the spinning solution, continues in the capillary and finishes after the droplet has left the capillary.

Raw materials of the electrostatic spinning solution can vary widely, comprising e. g. one or more self-organized polymers comprising covalently connected blocks, e. g. di-or triblock copolymers are preferred, but even multiblock copolymers are anticipated. Such polymers include chemically connected blocks, which repel each other, and tend to organize themselves in such a manner that a characteristic structure forms. The characteristic structures include for example lamella, cylindrical, or helical structures, or cavities inside the fiber. In cylindrical structures, it is possible that annular layers are formed outside the core of the fiber. One or more blocks can be degradable by UV radiation, reactive etching, or biodegradable. In another embodiment, selected nanodomains of the block copolymers are swollen with high boiling point plasticizers or homopolymers which remain in the nanodomains during the electrospinning but can be removed during a post-processing step by solvent treatment, dialysis, or thermal treatment or the like. Still, in another embodiment, the repulsive groups, as required for self-organization, are physically connected using hydrogen bonding, coordination, or proton transfer or the like. Without limiting the generality, such situation can be achieved by e. g. physically bonding amphiphilic oligomers along a polar polymer backbone or a block of a block copolymers. It is also possible to obtain fibers that have side chains, which protrude from the outer surface of the fiber giving a hairy impression of the surface of the fiber. Common to the fiber structures is that their specific surface area is large, typically 100-200 m2/g, but specific surface areas even up to 2000 m2/g are possible. In other words, the structure of the fiber comprises porous nanostructures. Typically those nanostructures are tubular or lamella. On one hand, by the method of the invention it is possible to manufacture the above-mentioned porous nanostructures, which may exist in a fiber having a conventional diameter. It is possible that the fibers having the conventional diameter can be split in later processing.

On the other hand, by the method of the invention, it is possible to manufacture from self-organized materials fibers, which diameters are equal or less than 1 micrometer. Further, fibers having at least one hollow tube in the length direction of the fiber, and having a diameter

between 1 and 20 nanometer can be manufactured by the method of the invention.

One important embodiment is to spin the nanostructured fibers in such a manner that the formed fibers become trapped into a fibrous structure, such as a nonwoven fabric (for example, a nonwoven fabric having a grammage between 10 and 30 g/m2 and comprising fibers, whose fineness is between 0,7 and 2,0 dtex), before they reach the receiving area. When a fibrous structure is placed in front of the receiving area, the formed fibers penetrate into the porous fibrous structure and at the same time they loose their kinetic energy and become trapped into the fibrous structure. In addition to the nonwoven fabric, the fibrous structure can be any structure, which is at least partially formed of fibers, such as a woven fabric, or a knitted fabric.

A central embodiment within the invention is post-processing, where selected domains of self-organized nano-structure are partially or totally emptied, cleaved, or degraded after the nano-scale fiber spinning.

The above-mentioned structures can be used for example to filtration.

The coarse fibers forming the basic fibrous structure form a mechanically strong network. The network comprises pores in which the fibers formed of at least one self-organized polymer remain. The above-mentioned fibers offer a large specific surface area to the filtration but they have a minor effect on the filtration speed. In other words, liquids or gases, which are due to be filtered, can easily permeate the filter.

The filters may be multilayered structures, which have fibrous sheet- like structures on top of each other. Each layer may include fibers formed of at least one self-organized polymer but the structure of the filter may include layers, which do not include such fibers. For example, coarse particles can be filtrated by a coarse fibrous structure, and after that the fluid can penetrate into a fibrous structure comprising fibers formed of at least one self-organized polymer. The layers of the filter can be attached to each other, or they can be loosely on top of each

other. The fibers formed of at least one self-organized polymer can be used also for adjusting electrical properties of the filter.

Besides the filtration, the structure comprising a fibrous network and fibers formed of at least one self-organized polymer can be utilized in various other uses, such as carriers for drugs, perfumes, or cosmetic substances, or functional structures in clothing and packaging.

In the electrostatic spinning method block copolymers can be used as raw materials. It is also anticipated that one or more additives, such as amphiphiles, surfactants, plasticizers, high boiling point oligomers, or homopolymers are selectively bonded or swollen within one or more blocks of block copolymers to form an integral part of the self- organized nanostructure within the fiber. The material self-organizes spontaneously and finally the additive, such as the amphiphile is cleaved off either by solvent extraction, dialysis, or thermal treatment.

For example, a polystyrene-block-poly (4-vinylpyridine) with the amphiphiles such as alkylphenols, or zinc dodecylbenzene sulfonates can be used. The self-organized polymers may vary widely, comprising functional groups such as ethers, esters, sulfonamides, amides, amines, acrylates, sulfonates, sulfonic acids, carboxylic acids, carboxylates, phosphates, and the like, such as polyethylenoxide, polyalkyethers with alkyl chain lengths from e. g. 1 to 20 methyl units, polyamides, polypeptides, aromatic polyamides, polyimides, polylactides, polyesters, polyethylene imines, polyurethanes, polyisocyanates, cellulosics, starch, chitosans, phenolics, conjugated polymer, or proteins. For example, a diblock polymer can be formed of polyethylenoxide in combination with polyamide, polystyrene, polyethylene, polypropylene; or polystyrene with polymethylmethacrylate, polyacrylic acid or polylactide ; or polyamides with polyalkylethers. Increasing the number of blocks and different architectures is fully anticipated. It is also anticipated that the block copolymer contains degradable blocks, which allow post processing with e. g. UV-radiation, reactive etching, biological degradation or the like, to open internal voids within the nano-scale fiber. Feasible block copolymers include also polyamide-polyalkyether segmented block

elastomers (so-called PEBAX), segmented polyurethane elastomers, and polystyrene-block-polyacrylic acid.

The additives may vary widely, and must be selected by their bonding and swelling capability to the specific domains of the self-organizing materials where they form the integral part of the nanostuctures.

Therefore their boiling point has to be high enough to withstand the electrospinning. However, they must be separately removable after the electrosopinning. Hydrogen bonding additives include substituted phenols, substituted di-or trihydroxybenzenes, substituted galates, sulfonamides, surfactants such as aliphatic or aromatic alkyl sulfonates or alkyl sulfonic acids or phosphates, polyglycolic compounds, such as glycerol, metal salts, and the like. Even low molecular weight homopolymers can be used to selectively bond to selected nanodomain and can be removed after the electrospinning.

The spinning solution comprises a solvent. The solvent can be any solvent, which is suitable for use in combination with the self-organized polymer in question. Suitable solvents include co-solvents, for example water, alcohols, acids, bases, or organic solvents. The spinning solution comprising the self-organized polymer and the solvent can have different viscosities, for example the spinning solution can be a gel. In addition to conventional solvents, monomers of each component of the block polymer can be used as the solvent. The spinning solution comprises typically 2-25 wt. -%, preferably 5-15 wt. -% of polymer.

The amount of the polymer depends on its molarity and desired viscosity.

The viscosity of the spinning solution is at least 125 cP, preferably it is between 200 and 1000 cP measured typically in process conditions of a processable spinning solution. Exceeding 1000 cP and finally 4000 cP increase the risk of the capillary blocking. An electrolyte or electrolytes may be added to reach higher conductivity in the electrostatic spinning process. To enhance the flowing properties, it is possible to use elevated temperatures, or add more solvent.

In the method of the invention, the spinning solution is prepared from at least one self-organized polymer and at least one solvent. The spinning solution may also contain more than one self-organized polymer, for example mixtures of two different self-organized polymers, each polymer having a specific internal organization and structure. The at least one self-organized polymer is allowed to unfoil in the solvent. The solvent swells the polymer, and the polymer chains start to open.

Typically, the spinning solution is first thin and running but when the unfoiling process proceeds further, the spinning solution changes into a gel or a jelly. The unfoiling process of the polymer can be promoted by stirring the solution.

According to the present invention the nano-domains can be produced in a controlled way in the sub-micron fiber. The polymer properties, especially the block length defines the structures to be formed and enables the control of the structures. The specific fibers can be produced by means of electrostatic spinning and can be post- processed further by means of selectively removing at least part of the fiber. Finally the controlled nano-domains can be utilized in various ways of preparation of advanced nano-structures. The structures are useful in applications such as precursors for nano-tubes, controlled textured surfaces, and porous structures and systems suitable to be used in nano-devices, selective filters, catalysts, drug delivery materials, sensors, and other application where the nano-domains should be prepared in controlled manners.

Alternatively the fiber structure can be fragmented simply mechanically, or thermally separating the phases from each other.

In the following, the invention is described by referring to examples and figures in which Figs. 1 and 2 show schematic views about an apparatus for performing the method for manufacturing a fiber, and Fig. 3 shows a cross-sectional view of a fiber manufactured by the method of the invention.

In a process according to figure 1, a spinning solution is fed through a capillary 2. Outside the capillary 2 the spinning solution forms a conical shape due to an electric field prevailing between the capillary 2 and the receiving area 5. The capillary 2 is in a first potential, which is provided by a high voltage power supply 1.

A receiving area 5, which is in a second potential (for example, grounded-grounding is denoted in the figure by the number 6), collects formed fibers. A continuous fiber, which is spun through the capillary 2 spreds to staple fibers 4 due to the electric field.

In a process according to figure 2, a spinning solution is fed through a capillary 2. The capillary 2 is in a first potential, which is provided by a high voltage power supply 1.

In front of a receiving area 5, which is in a second potential (for example, grounded-grounding is denoted in the figure by the number 6), there is a fibrous structure 7, such as a nonwoven fabric, which collects formed fibers on its surface. In the figure 2, there is a batch process but also a continuous process according to the same principle is possible. In the continuous process it is possible for example to attach different layers together in the same process step.

Figure 3 describes a transmission electron microscope picture of electrospun diblock copolymer polystyrene-block-poly (4-vinylpyridine) where pentadecyl phenol molecules are hydrogen bonded to the latter block, thus controlling the self-organization due to their mutual physical bonding. Importantly and astonishingly, the example shows that physically bonded self-organized materials can be electrospun, i. e. that physical interactions can be selected to withstand the harsh electrospinning conditions. Secondly, the internal self-organized nanostructure is evident, showing self-organized nanodomains of sizes of ca. 20 nm. This is compatible with the molecular weights of the used polymer blocks. Finally, the pentadecyl phenol molecules can be selectively cleaved from the (dark) domains, thus leaving an open framework with substantial internal porosity.

Example 1.

Polystyrene-block-poly (4-vinyl pyridine) (PS-block-P4VP) with the polydispersity of 1.23 was provided by-Polymer Source Inc. and has molecular weights of the PS-and P4VP-blocks of 238 100 g/mol and 49 500 g/mol, respectively. 3-n-pentadecylphenol (PDP) obtained from Aldrich (purity 98 wt %) was further purified by recrystallizing twice using petrol ether. From the prior art, it is known that pentadecylphenol hydrogen bonds to the poly (4-vinyl pyridine) chains, leading to self- organization in the bulk and film phase. In the present case, solutions of concentrated PS-block-P4VP (ca. 12 wt %) and PDP (ca. 16 wt %) were first made using N, N-dimethylformamide (DMF) (Riedel-de-Haen, purity 99 wt %). The solutions consisting of PS-block-P4VP and PDP were mixed to render PS-block-P4VP (PDP) 1.0 where nominally one PDP molecule corresponds to each pyridine group. The concentration of the solution is 13 wt %, which yielded high enough viscosity for electrospinning.

A capillary having an inner diameter of 1,6 mm and length of 27 mm was used. The distance between the tip of the capillary and the receiving area was 175 mm. The receiving are was perpendicular to the length direction of the capillary. The potential of the capillary was 10 kV and the potential of the receiving area was-10 kV. The measured strength of the electric field was 1,1 kV/cm.

Optical microscopy showed pearl necklace type of fibers.

Example 2.

The example 1 was repeated, but the potential of the capillary was 20 kV and the potential of the receiving area was-20 kV. The measured strength of the electric field was 2,3 kV/cm.

More uniform fibers were achieved.

Example 3.

As example 1 but the potential of the capillary was 30 kV and the potential of the receiving area was-30 kV. The measured strength of the electric field was 3,4 kV/cm In this case, uniform nano-scale fibers were produced with a diameter of ca. 400 nm. The fibers were embedded in epoxy and cured. After microtoming, the cross-section was inspected using transmission electron microscopy and self-organized domains were observed, see Fig. 3. In this picture, the dark colours represent the poly (4-vinyl pyridine)/pentadecyl self-organized nanodomains, which have sizes of the order 20 nm. The bright colour inside the circular fiber periphery is due to polystyrene which appears in the figure similar as the epoxy background outside the periphery.

It is crucially important to verify that the oligomeric pentadecyl phenol, controlling the self-organization, will remain hydrogen bonded to the poly (4-vinylpyridine) even after the extreme conditions of electrostatic spinning. Therefore, electrospun fibers were inspected using NMR whether the presence of the amphiphiles could be verified. A clear evidence is given in 1H NMR spectrum as the methyl peak (8=0, 89 (CH3, PDP) ) provides estimation of the complexation stage in reasonable accuracy, when the integral of aromatic hydrogen is compared to integral of hydrogen locating methyl groups. It is astonishingly concluded that most of the pentadecyl phenol remains in the sample after electrospinning. One can conclude that physically bonded self-organized polymers can be electrospun.

However, the pentadecylphenol can be removed from the poly (4- vinylpyridine)-containing self-organized nanodomains by exposing the nanoscale fiber in methanol for extended periods of time, e. g. for several days. Therefore, very open and porous internal structure is obtained.

Example 4.

As example 3 but a nonwoven fabric was placed between the capillary and the receiving area in such a manner that the nonwoven fabric is parallel to the plate serving as the receiving area.

Thin fibers formed of a self-organized polymer, in this case polystyrene-block-poly (4-vinylpyridine)/pentadecylphenol, were observed after each trial described in the examples 1-4. The sample, which was obtained from a process described in example 4, included fibers formed of a self-organized polymer between the conventional fibers of the nonwoven fabric.

Finally, it is totally anticipated that electrospun fibers with internal structure can be prepared e. g. from polystyrene-block- polymethylmethacrylate or polystyrene-block-polylactic acid and by degrading the polymethylmethacrylate or polylactic acid domains after the spinning process in such a manner that porous fibers can be made.

The examples are not used to limit the generality of the present invention.

Example 5 Polystyrene-block-poly (4-vinylpyridine) (PS-block-P4VP) with the polydispersity of 1.23 was provided by Polymer Source Inc. and has molecular weights of the PS-and P4VP-blocks of 238 100 g/mol and 49 500 g/mol, respectively. 3-n-pentadecylphenol (PDP) obtained from Aldrich (purity 98 wt %) was utilized, after purification e. g. after recrystallizing PDP twice out of petrol ether. From the prior art, it is known that pentadecylphenol hydrogen bonds to the nitrogen in poly (4-vinyl pyridine) chains, leading to self-assembly in the bulk and film. In the present case, solutions of concentrated PS-block-P4VP (ca.

12 wt %) and PDP (ca. 16 wt %) were first made using N, N- dimethylformamide (DMF) (Riedel-de-Haen, purity 99 wt %). Thereafter solutions consisting of PS-block-P4VP and PDP were mixed to render PS-block-P4VP (PDP) 1. 0, where nominally one PDP molecule corresponds to each pyridine group. The concentration of the solution was 13 wt %, which yielded high enough viscosity for electrospinning.

A capillary used in the electrostatic spinning has an inner diameter of 1,6 mm and length of 27 mm. The distance between the tip of the capillary and the receiving area was 175 mm. The receiving are was perpendicular to the length direction of the capillary. The potential of the capillary was 30 kV and the potential of the receiving area was-30 kV. The measured strength of the electric field was 3,4 kV/cm.

In this case, uniform nano-scale fibers were produced with a diameter of ca. 400 nm. And within the fibers supramolecular entities self- assembled to nanostructures where P4VP (PDP) as a minor phase formed nano-domains in to the polystyrene matrix. The pentadecylphenol can be removed from the poly (4-vinylpyridine) domains by exposing the nano-fibers in methanol for extended periods of 48 fours. This example shows that the substructures can be cleaved selectively by a solvent treatment.

Example 6 Three differentiated polystyrene-block-poly (4-vinylpyridine) were applied according to the table below. The PS-block-P4VP diblock copolymers were hydrogen bonded stoichiometric with respect to the number of pyridine groups with the pentadecylphenol, to obtain PS-b- P4VP (PDP) 1. o. PS-block-P4VP (PDP) I. o supra-molecules were made out of concentrated N, N-dimethylformamide (DFM) solutions. The solutions were supplied to 18 gauge needle having voltage of 30 kV... 50 kV according the table below. The electrospun fibers were collected onto polyimide film attached on the edge of the rotating disc collector. The distance between the tip of the needle and the surface of the collector disc was 100 mm. The surface speed of the collector for each material was 29m/sec and 35 m/sec respectively. The formed fiber ribbons can be further processed (as described in the example 1) to produce porous fibers or sub-fibers by means of fibers cleavage.

Raw materials, spinning conditions and formed sub-structures are presented in table 1.

Table 1. Raw materials, spinning conditions and formed sub-structures. Sample Material Mw Mw (P4VP) Polymer Voltage Surface Sub (PS) g/mol in DFM KV speed Structure g/mol wt % m/sec 3.1. 1 PS-b-365 29400 15 30 29 <20 nm P4VP (PDP) 1. 0 000 fiber 3.1. 2 PS-b-365 29400 15 30 35 <20 nm P4VP (PDP) 1.0 000 fiber 3.2. 1 PS-b-301 19600 15 30 29 <20 nm P4VP (PDP) 1.0 000 fiber 3.2. 2 PS-b-301 19600 15 30 35 <20 nm P4VP (PDP) 1.0 000 fiber 3.3. 1 PS-b-56 300 43 500 15.30 29 <20 nm P4VP (PDP) 1. 0 fiber 3.3. 2 PS-b-56 300 43 500 15 50 35 <20 nm P4VP (PDP) 1. 0 fiber

Example 7 Polyamide 6.6 was dissolved in formic acid to form a 10 wt-% solution.

The viscosity of the solution was 235 cP. The solution was supplied to the 18-gauge needle having voltage of 35 kV. The electrospun fibers were collected on to the edge of the rotating collector. The distance between the tip of the needle and the surface of the collector disc was 150 mm. The surface speed of the edge was 22 m/sec. Fibers were partially oriented in the ribbons formed. The ribbons were cut and treated mechanically. The ribbons fractured and formed a nano-fiber net.

Example 8 Polystyrene-block-polymethylmethacrylate PS-b-PMMA is electrospun. After the spinning process the polymethylmethacrylate domains are selectively degraded by means of intensive UV-radiation, for example with mercury UV lamp with maximum emission at 254 nm.