EP1485526A1 - Procede de production de fibres creuses - Google Patents

Procede de production de fibres creuses

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Publication number
EP1485526A1
EP1485526A1 EP03743870A EP03743870A EP1485526A1 EP 1485526 A1 EP1485526 A1 EP 1485526A1 EP 03743870 A EP03743870 A EP 03743870A EP 03743870 A EP03743870 A EP 03743870A EP 1485526 A1 EP1485526 A1 EP 1485526A1
Authority
EP
European Patent Office
Prior art keywords
hollow fibers
pores
polymer
liquid
template
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP03743870A
Other languages
German (de)
English (en)
Inventor
Ralf Wehrspohn
Kornelius Nielsch
Martin Steinhart
Andreas Greiner
Joachim Wendorff
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Transmit Gesellschaft fuer Technologietransfer mbH
Original Assignee
Max Planck Gesellschaft zur Foerderung der Wissenschaften eV
Transmit Gesellschaft fuer Technologietransfer mbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Max Planck Gesellschaft zur Foerderung der Wissenschaften eV, Transmit Gesellschaft fuer Technologietransfer mbH filed Critical Max Planck Gesellschaft zur Foerderung der Wissenschaften eV
Publication of EP1485526A1 publication Critical patent/EP1485526A1/fr
Withdrawn legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/08—Hollow fibre membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0039—Inorganic membrane manufacture
    • B01D67/0069—Inorganic membrane manufacture by deposition from the liquid phase, e.g. electrochemical deposition
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0039—Inorganic membrane manufacture
    • B01D67/0072—Inorganic membrane manufacture by deposition from the gaseous phase, e.g. sputtering, CVD, PVD
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0081—After-treatment of organic or inorganic membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/08—Hollow fibre membranes
    • B01D69/081—Hollow fibre membranes characterised by the fibre diameter
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/12—Composite membranes; Ultra-thin membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/02—Inorganic material
    • B01D71/022—Metals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/02—Inorganic material
    • B01D71/022—Metals
    • B01D71/0221—Group 4 or 5 metals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/02—Inorganic material
    • B01D71/022—Metals
    • B01D71/0223—Group 8, 9 or 10 metals
    • B01D71/02231—Palladium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/02—Inorganic material
    • B01D71/022—Metals
    • B01D71/0223—Group 8, 9 or 10 metals
    • B01D71/02232—Nickel
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/28—Polymers of vinyl aromatic compounds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/28—Polymers of vinyl aromatic compounds
    • B01D71/281—Polystyrene
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/30—Polyalkenyl halides
    • B01D71/32—Polyalkenyl halides containing fluorine atoms
    • B01D71/34—Polyvinylidene fluoride
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/30—Polyalkenyl halides
    • B01D71/32—Polyalkenyl halides containing fluorine atoms
    • B01D71/36—Polytetrafluoroethene
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/40—Polymers of unsaturated acids or derivatives thereof, e.g. salts, amides, imides, nitriles, anhydrides, esters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/40—Polymers of unsaturated acids or derivatives thereof, e.g. salts, amides, imides, nitriles, anhydrides, esters
    • B01D71/401—Polymers based on the polymerisation of acrylic acid, e.g. polyacrylate
    • B01D71/4011—Polymethylmethacrylate
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/52—Polyethers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/52—Polyethers
    • B01D71/522—Aromatic polyethers
    • B01D71/5221—Polyaryletherketone
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/52—Polyethers
    • B01D71/522—Aromatic polyethers
    • B01D71/5222—Polyetherketone, polyetheretherketone, or polyaryletherketone
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D5/00—Formation of filaments, threads, or the like
    • D01D5/24—Formation of filaments, threads, or the like with a hollow structure; Spinnerette packs therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2323/00—Details relating to membrane preparation
    • B01D2323/08—Specific temperatures applied
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2323/00—Details relating to membrane preparation
    • B01D2323/08—Specific temperatures applied
    • B01D2323/082—Cooling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2323/00—Details relating to membrane preparation
    • B01D2323/24—Use of template or surface directing agents [SDA]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/00781—Aspects relating to microreactors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0065—Solid electrolytes
    • H01M2300/0068—Solid electrolytes inorganic

Definitions

  • the invention relates to a process for the production of hollow fibers, in particular for the production of mesotubes and nanotubes, in which the tubes or hollow fibers are preferably oriented in one direction with an inner diameter in the nano to micrometer range, and the use thereof.
  • This invention further relates to the hollow fibers or tubes produced by the process and porous composite materials containing them.
  • Tubes or hollow fibers with an inner diameter of ⁇ 0.1 mm are also referred to as mesotubes or nanotubes.
  • nanotubes made of polymer materials in particular have become important because they can be used for various purposes, e.g. For storing or transporting gases or liquids, in fuel cells, in near-field optics, in nanoelectronics and in combinatorial chemistry, as well as in the areas of catalysis and drug delivery.
  • Regular arrangements of nanotubes are of particular interest since they e.g. are also suitable for use in filtration, hydrogen storage, tissue production or for photonic crystals.
  • nanotubes for separation purposes is also known, for example in medical dialysis, for gas separation or osmosis in aqueous systems, for example for water treatment (see Kirk Othmer, Encyclopedia of Chemical Technology, 4 Ed. Vol 1 3, p. 31 2 -31 3).
  • the tube material mostly consists of polymers, which can also have pores, ie properties of semipermeable membranes.
  • the for separation purposes The hollow fibers used usually have a surface area of 100 cm 2 / cm 3 volume with an inner diameter of 75 ⁇ m to 1 mm.
  • Superconducting fibers with a diameter of approx. 60 ⁇ m are produced here by filling hollow fibers made of polymers with a mass which, after thermal degradation of the polymer, has superconducting properties (JCW Chien, H. Ringsdorf et al., Adv. Mater., 2 (1 990), p. 305).
  • Tubes with an inner diameter of 2 ⁇ m or larger can be produced by extrusion spinning processes.
  • a number of extrusion spinning processes are described in Kirk-Othmer, Encyclopedia of Chemical Technology, 4th Ed. Vol. 1 3, p. 31 7-322. The production of hollow fibers with smaller inner diameters is not possible with this process.
  • US-A-4,689,186 describes an electrospinning process for the production of tubular products with a rotating spindle, in which an auxiliary electrode is used to deposit a part of the fibers in the stretched state oriented in the direction of the circumference of the circle, so that after removing the rotating spindle by pulling the tensioned together Fiber jacket a smaller diameter of the tube is achieved.
  • this process is complex and limited in terms of the materials suitable for it.
  • nanotubes can be polymerized in the pores of nanoporous materials, the polymerization beginning on the walls of the pores and, depending on the duration of the polymerization, tubes with a defined wall thickness or compact, filled nanofibers being obtained, such as by C.R. Martin in Science 266 (1 994), p. 1 961 ff.
  • the shape of the template is reproduced.
  • thin fibers are produced as a template by means of an electrospinning process, which e.g. be coated with polymers by chemical vapor deposition.
  • the fibers used as a template are removed by pyrolysis or extraction.
  • Nanotubes made from poly-p-xylylene By coating the template fibers by means of spin coating, nanotubes can be made from a variety of polymers.
  • Such a process for the production of hollow fibers describes e.g. DE 100 23 456 A1.
  • Both known template processes are relatively complex because they require either a polymerization step within the template or a gas phase deposition step on the template.
  • the processes are also restricted to certain feedstocks.
  • the process is also intended to enable the processing of a large number of materials, the controlled setting of properties of the resulting hollow fibers, for example with regard to shape and size, material composition, morphology, structuring, and the controlled regular arrangement of hollow fibers with lateral dimensions down to the square centimeter range.
  • This object is achieved by a method for producing hollow fibers from non-polymeric materials with external diameters from 10 nm to 100 ⁇ m, preferably 10 nm to 50 ⁇ m, which contain at least one polymer, comprising the steps
  • Another object of the invention is a method for producing hollow fibers from non-polymeric materials with outer diameters from 10 nm to 100 ⁇ m, comprising the steps: (a) providing a porous template material,
  • hybrid materials containing hollow fibers which are obtainable by solidifying the polymer-containing liquid in the pores of the template material, and the hollow fibers obtainable by at least partially removing the template material, which are preferably essentially free of the template material.
  • the hollow fibers can optionally have a plurality of polymer components in predetermined mixing ratios and / or areas of different material composition. If mixtures which contain selectively removable polymers and non-polymeric material are used to wet the template, nanotubes can be produced from the non-polymeric material by removing the polymers. This can be converted chemically if necessary. Such nanotubes preferably contain transition metals or their oxides as wall material.
  • the hollow fibers can have structured, porous or / and incomplete, for example channel-shaped, jacket surfaces.
  • Another object of the invention is arrangements of hollow fibers, characterized in that several hollow fibers are arranged in parallel, in particular regular arrangements of hollow fibers, preferably in hexagonal, trigonal, square or graphite grids, particularly preferably over lateral areas from 1 ⁇ m 2 to 500 cm 2 , in particular from 25 mm 2 to 10 cm 2 .
  • An advantage of the method according to the invention is that both functionalized and non-functionalized polymers can be used to produce hollow fibers. It is even possible to use polymers which have additives, polymer mixtures and polymers with special molecular architectures, such as, for example, block copolymers, dendrimers, graft copolymers or polymer brushes.
  • non-polymeric materials are metal-containing compounds such as metal salts, e.g. Compounds of platinum, palladium, nickel, silver, ruthenium, manganese, titanium, chromium or another transition metal or combinations of different transition metals.
  • Design of the molecular weight distribution can be freely selected within wide limits when using the method according to the invention. Another advantage is that no complex polymerization step or gas separation step on the template is necessary. Another one
  • the advantage is that the properties of the hollow fibers can be controlled over a wide range, preferably through those that are brought about in a targeted manner
  • the degree of crystallinity of the hollow fibers can be adjusted by choosing suitable process parameters. In case of
  • Processing of material mixtures can be done in the filled Te mpl ate ndu rc h H e rb e u r u ng th ermischindu rt r phase separation processes and differently long ripening times specifically produce binodal or spinodal segregation morphologies. Phase transitions can also be brought about by changing the composition of the liquid material, preferably by evaporating a volatile component. Structured hollow fibers of this type can be further functionalized. For example, individual phases can be selectively removed or selectively crosslinked from hollow fibers in which phase separation is present in amorphous and crystalline regions and / and regions of different material composition. If there are substances in the wall material which contain metal atoms or ions, for example salts or organometallic precursor compounds, these can be converted into the metals by means of suitable methods, for example by reduction and / or pyrolysis.
  • the hollow fibers can also have structured outer surfaces and a cylindrical or other cross-section, depending on the template used.
  • the process is particularly suitable for the production of hollow fibers which have a high surface / volume ratio, which is of great interest, for example, for applications in the field of catalysis or for storage media, of hollow fibers with specific wetting and adhesive properties or of hollow fibers with areas of different material composition and hollow fibers, the properties of which are modified by low molecular weight additives.
  • viscous polymer-containing liquids penetrate into porous template materials in such a way that at least over a large area of the template material the walls are wetted without simultaneously completely filling the pores. It was therefore surprising that when a polymer-containing liquid is introduced into a porous template material, the pores are initially wetted by a thin film and the processes of wall wetting and the complete filling of the pores can be dissolved in time. To the complete To prevent filling of pores, the liquid source can be removed and / or the filling process can be interrupted, for example, by thermal quenching, for example cooling or evaporation of solvents.
  • FIG. 1 shows snapshots of such a wetting process. It can be seen that when the liquid penetrates the pores, a thin film initially forms which covers the surface. Depending on the material and the material properties, the thickness of the film can range from less than 100 nm, even down to a few angstroms, in the range of a molecular monolayer. The film thickness is particularly dependent on the interactions between the liquid forming the film and the surface substrate. Therefore, combinations of liquid and substrate are preferably used which have a contact angle close to zero. The pore walls are then completely wetted very quickly.
  • the method according to the invention is characterized in that the pores of a template are wetted by a liquid material which has at least one polymer and the liquid material is solidified after the wetting.
  • the solidification comprises passing through the glass transition of at least one polymer component contained in the liquid.
  • the solidification comprises crystallization if the liquid contains at least one polymer component capable of crystallization. Crystallization can be brought about, for example, by changing the material composition of the liquid material, for example by evaporating a solvent, or / and by changing the temperature.
  • the template material is a body that has pores.
  • the template preferably has pores arranged in parallel or almost in parallel.
  • Templates with parallel pores are particularly preferred.
  • the aspect ratio of the pores is preferably 1 to 20,000, particularly preferably from 10 to 20,000 and very particularly preferably from 1,000 to 20,000.
  • the aspect ratio is the quotient of the length of the pores by the average width (average internal diameter) of the pore.
  • Templates which have pores with an average pore width of 10 nm to 100 ⁇ m, preferably 10 nm to 50 ⁇ m, particularly preferably 10 nm to 5 ⁇ m and very particularly preferably 50 nm to 1 ⁇ m.
  • the template used preferably has pores which have a deviation from the mean pore width of ⁇ 5%, particularly preferably ⁇ 2% and very particularly preferably ⁇ 1%.
  • Templates are preferably used for the method in which the arrangement of the pores has a short-range order, particularly preferably templates in which the arrangement of the pores has a short-range order and a long-range order.
  • the process according to the invention preferably produces hollow fibers which have a wall thickness of ⁇ 1 ⁇ m, preferably from 1 nm to 1 ⁇ m, particularly preferably from 5 nm to 500 nm and very particularly preferably from 10 nm to 100 nm.
  • the template Before wetting the template with the polymer-containing liquid, it can be advantageous if the template is cleaned. This can be done in a manner known to the person skilled in the art. So can a cleaning through The template material is brought into contact with a suitable cleaning agent, for example by means of an acid, a base, an organic solvent, water or combinations thereof, with the proviso that the template material itself is not destroyed by the cleaning agents used.
  • a suitable cleaning agent for example by means of an acid, a base, an organic solvent, water or combinations thereof, with the proviso that the template material itself is not destroyed by the cleaning agents used.
  • Suitable template materials are porous solids based on organic and / or inorganic materials, such as porous organic polymer membranes, porous metal oxides, porous ceramics, porous metals or semimetals, and porous semiconductors. Templates made of porous aluminum oxide or porous silicon are particularly preferably used, the templates preferably meeting the abovementioned conditions with regard to pore size.
  • suitable templates is known, for example, from microsystem technology, semiconductor technology and metal oxide alloy. With standard procedures, e.g. Plasma etching can be used to display templates that have pores with an aspect ratio of ⁇ 50.
  • Commercially available materials that are suitable as templates are e.g. porous aluminum oxide or polycarbonate membranes. These usually have pore diameters of 10 nm to 250 nm.
  • Porous aluminum oxide materials that are produced by self-assembly are particularly suitable as templates.
  • the electrochemical production of suitable porous aluminum oxide by self-assembly with pore diameters from 10 nm to 400 nm is described, for example, by H. Masuda and K. Fukuda (Science, 268 (1 995), p. 1466).
  • the deviation of the average pore size is less than 10%.
  • nano-indentation H. Masuda et al., Appl. Phys. Lett. 71 (1997), p. 2770
  • AP Li et al. Electrochem. Sol.-State Lett 3 (2000), p.
  • porous aluminum oxide materials are available which are suitable as templates.
  • Templates based on porous silicon which can be produced, for example, by electrochemically etching silicon, are also suitable. Their preparation is described for example in US-A-4,874,484. Regular templates with very smooth pore walls are obtained, the pores having a perfect cylindrical shape.
  • the pores of the preferred versions of the silicon templates have diameters from 200 nm to 10 ⁇ m. It can be advantageous to thermally oxidize silicon templates during production, so that a 5 nm to 20 nm thick silicon oxide layer forms the pore wall. In this way, the surface can be made highly energetic and thus the adhesion of liquid materials can be improved. In addition, the thermal oxidation smoothes the pore surfaces.
  • hollow fibers with a wide variety of external shapes or cross sections can be produced. Pores can also be created with shapes that deviate from the cylindrical shape (H. Masuda, H. Asoh, M. Watanabe, K.
  • Template structures can also be produced which, starting from the main pores, have defect pores or connecting pores between the main pores.
  • the defect pores are used in the manufacture of the
  • templates e.g. Silicon template used, the defect pores originating from main pores, the diameter of which is smaller than that of the main pores.
  • Such hollow fibers have an increased surface / volume ratio, which is advantageous for a large number of applications. Modified adhesive, adsorption, adhesion and / or wetting properties are also found.
  • templates e.g. Silicon template used, which have connecting pores starting from the skin pores to other main pores, the diameter of which is preferably smaller than that of the main pores.
  • the hollow fiber arrangements obtained are distinguished after the removal of the template material in that the hollow fibers are connected to one another by images of the connecting pores. These connections stabilize the fiber arrangement and are particularly advantageous in the case of free-standing hollow fiber membranes.
  • the liquid can be introduced into the template material as a polymer-containing melt, for example as a melt of a polymer or a mixture of several polymers, which may contain further additives.
  • the melt can be made by heating the material to a temperature above the solidification temperature of the polymer or polymer blend.
  • the melt is very particularly preferably produced by heating the material to a temperature which is at least 2%, preferably at least 10% and very particularly preferably 30%, above the solidification temperature of the polymer or the polymer mixture.
  • films, powders or granules of a polymer for example powders of polystyrene
  • a porous template for example, films, powders or granules of a polymer, for example powders of polystyrene
  • This arrangement is brought to a temperature above the glass transition temperature of polystyrene and for a certain time the polymer is allowed to run into the pores and thereby the pore walls wetted. Before the pores themselves are filled with the polymer, the arrangement is quenched to room temperature, for example. It is also possible to melt the powder of the polymer so that a liquid material is formed and to immerse the template with the pore surface in the liquid material. By reducing the surface energy, the pore walls are also wetted here.
  • the liquid can be solidified by cooling the melt.
  • the solidification of the liquid material is preferably achieved by cooling to temperatures below 50 ° C., preferably below 30 ° C. and very particularly preferably by cooling or quenching to room temperature.
  • the entire template is usually cooled or quenched with the liquid material that wets the walls of the pores.
  • the degree of crystallinity can be set by selecting suitable cooling rates and by tempering the filled templates at a temperature above the glass transition temperature and below the melting temperature.
  • the polymer-containing liquid can also be used as a solution, suspension or / and emulsion of a polymer or a mixture of polymers, which may also contain additives, in a carrier or
  • Carrier mixture are introduced into the template material, the polymer-containing liquid preferably being present as a solution.
  • Carriers are suitable substances which dissolve, suspend or emulsify the polymer or the polymer mixture and, if appropriate, the additives, without destroying the materials used.
  • Examples of carriers are organic solvents such as ethanol,
  • Liquid can be immersed in the template with the porous surface or the solution can be dripped on.
  • the pore walls are wetted by the liquid material.
  • the inner walls of the pores are wetted even if liquid is dropped onto a rapidly rotating template.
  • the liquid material can be solidified by removing the carrier. It may be advantageous to support evaporation by using elevated temperatures. Ultrasound can be applied while the liquid is being introduced into the template. This leads to an additional structuring of the fibers.
  • the source of the liquid material must be removed after a predetermined period of time, after sufficient wetting of the walls of the pores has taken place. This can e.g. can be achieved by taking the template out of the liquid or by making the liquid medium in the solid state, e.g. by solidifying the melt and / or removing the carrier.
  • the polymer present in the liquid material has, for example, an average number average molecular weight (Mn) of more than 500 D, in particular more than 5,000 D, preferably more than 50,000 D, particularly preferably more than 100,000 D, even more preferably more than 500,000 D and most preferably more than 1,000,000 D. It can be selected from
  • organic polymers such as poly (p-xylylene), polyetherimides, polyaryl ether ketones, polysulfones, poly (phenylene sulfides), polyacrylamides, polyimides, polyesters, polyolefins, polystyrenes, pol ⁇ carbonates, polyamides, polyethers, polyphenylenes,
  • organic polymers such as poly (p-xylylene), polyetherimides, polyaryl ether ketones, polysulfones, poly (phenylene sulfides), polyacrylamides, polyimides, polyesters, polyolefins, polystyrenes, pol ⁇ carbonates, polyamides, polyethers, polyphenylenes,
  • Polybutylene terephthalate polymethacrylonitriles, polyacrylonitriles, polyvinyl acetates, neoprene, Buna N, polybutadiene, or halogenated polyolefins, e.g. Polyvinylidene fluoride or polytetrafluoroethylene as well as dendrimers, (ii) biological polymers such as polysaccharides, e.g. cellulose
  • Repeating units preferably in the form of block copolymers, graft copolymers or dendrimers, their homo- or
  • Copolymers or / and mixtures.
  • the liquid material according to the invention particularly preferably has a polymer selected from polystyrenes, polyamides or polymethyl methacrylates.
  • Polymers with special architectures such as, for example, block copolymers, dendrimers or graft copolymers, polymer brushes and / or mesogens-containing polymers can also be used.
  • a template with pores is first obtained, the walls of which are coated with a polymer-containing material. If the polymer-containing coating contains non-polymeric materials, the polymeric components can at least partially be removed selectively, so that a hybrid structure results, which is characterized by pore walls coated with the non-polymeric material. This non-polymeric material can still be chemically converted.
  • a thermally degradable polymer and a metal-containing compound which is preferably selected from components which (i) are a metal, in particular platinum, palladium, gold, silver, nickel, rhodium, ruthenium, manganese, titanium or Contain chromium, another main group or transition metal or combinations of different metals,
  • an organometallic compound or another metal-containing compound in particular platinum, palladium, gold, silver, nickel,
  • the metal-containing compound can then be converted by suitable methods, for example metal-containing compounds, such as organometallic compounds, can be converted into metals or metal oxides, or semiconductor precursors can be converted into semiconductor compounds. If a transition metal precursor is used as the metallic compound, the polymer can be removed by pyrolysis of the filled template or in some other way and the transition metal can be converted into the metallic state. The result is an array of metal-coated microcavities.
  • Hybrid structures of this type are suitable for a number of applications, for example as a microcuvette array in combinatorial materials and active ingredient research or as a photonic crystal.
  • the hybrid structures preferably contain uniform pores with a size that deviates from the mean pore size, less than 5%, particularly preferably less than 1%. A regular one can be particularly advantageous here Arrangement of the pores, for example in a hexagonal, trigonal or square grid or in a graphite grid, for example for the controllability of individual pores.
  • the method according to the invention is particularly suitable for processing materials which are liquid in the melt or in solution or emulsion and which are converted into a solidified state by suitable measures.
  • This also includes materials and material mixtures, the properties of which can be specifically adjusted during or / and after wetting the pores of the template. This can e.g. done by bringing about a phase transition.
  • a phase transition can be induced, for example, by changing the material composition of the liquid material, preferably by evaporating a volatile component.
  • a particularly advantageous method is to bring about a phase transition through a change in temperature. In this case, the process can be precisely controlled by controlling the process temperature.
  • phase transition can take place, for example, in the form of a transfer of a homogeneous material into a state in which areas of different material composition are present. Likewise, amorphous and crystalline areas can be formed from a homogeneous material. However, phase transitions can also affect changes in electrical or magnetic material properties. If the liquid material is a mixture of materials, a phase transition can also manifest itself through a changed wetting behavior with regard to the pore wall material.
  • a liquid material is used Material mixture that is subjected to a phase separation process. This creates areas of different material composition in the outer surfaces of the fibers.
  • An embodiment is preferred which leads to a spinodal segregation process. If segregation takes place in a phase of a non-volatile material and a volatile material, pores are formed from the regions in which the volatile material was located, for example after its disappearance.
  • the non-volatile material can, for example, have a polymer, the volatile material, for example, a low molecular weight carrier.
  • phase having at least one polymer can be selectively removed. This can preferably be done thermally, chemically, biologically, radiation-induced, photochemically, by plasma, ultrasound, microwaves or / and extraction with a solvent.
  • the morphology can mature.
  • spinodal segregation a state can exist immediately after the segregation has started, in which the two coexisting phases have interfaces to the pore wall and form a fine interpenetrating morphology.
  • a situation may have arisen in which, for example, a bowl-shaped morphology analogous to an interface-oriented spinodal segregation is present.
  • the ripening process can be frozen at a selected point in time, for example by a change in temperature.
  • hybrid hollow fibers are those hollow fibers, the inner surface of which made of a chemically resistant material and the outer surface of which consists of a mechanically stable material.
  • the template In order to be able to use the hollow fibers or nano or mesotubes without the template, the template has to be at least partially removed after the liquid material has solidified.
  • the template can be removed thermally, chemically, biologically, radiation-induced, photochemically, by plasma, ultrasound, microwaves and / or extraction with a solvent.
  • the template is preferably removed by chemical and / or thermal means
  • the template is removed e.g. with a
  • Alkali preferably with an aqueous potassium hydroxide solution or an acid, preferably H 3 P0 4 for aluminum oxide or HF / HN0 3 mixtures for silicon.
  • hollow fibers or hollow fiber arrangements are accessible.
  • the hollow fibers can be closed at both ends, open at one or both ends.
  • hollow fibers produced according to the invention can be used to produce nonwovens or fabrics.
  • Hollow fiber arrangements are obtained due to adhesive forces between the individual hollow fibers. It may be advantageous if the hollow fibers of the individual pores are connected to one another via polymer material, the connecting polymer material being residues of the polymer which has been applied to the template, melted and then solidified, or may result from the filling of the connecting pores located between the main pores of the template. Hollow fiber arrangements with a long-range order predetermined by the template with a lateral extension into the region of several can be used Create a square centimeter. Arrangements of hollow fibers represent nanostructured surfaces. Such surfaces have specific adhesive properties (K. Autumn, YA Liang, ST Hsieh, W. Zesch, WP Chan, TW Kenny, R. Fearing, RJ Gear, Nature 405 (2000), p. 681 ) and specific wetting properties (W. Chen, AY Fadeev, MC Hsieh, D. ⁇ ner, JP Youngblood, TJ McCarthy, Langmuir 1 5 (1 999), p. 7238).
  • hollow fibers according to the invention or manufactured according to the invention or arrangements of hollow fibers can be used as components in medical devices, e.g. artificial lungs, used in microelectronics as wire, cable or capacitance, as waveguide, in super lightweight construction technology, in medical separation techniques, in capillary electrophoresis, in scanning probe microscopy, in catalytic systems, in fuel cells, in batteries or in electrochemical reaction apparatus.
  • medical devices e.g. artificial lungs, used in microelectronics as wire, cable or capacitance, as waveguide, in super lightweight construction technology, in medical separation techniques, in capillary electrophoresis, in scanning probe microscopy, in catalytic systems, in fuel cells, in batteries or in electrochemical reaction apparatus.
  • hollow fibers according to the invention or those produced according to the invention are suitable for use as a sensor component, as a microreactor, as a protein store, as a drug delivery system, as a composite material, as a filler, as a mechanical reinforcement, as a heat insulator, as a dielectric, as an interlayer dielectric in chip production, as a separation medium, as a storage medium for gases, liquids or particle suspensions or as a material in the clothing industry.
  • the hollow fibers according to the invention can be used as heat insulators in clothing or sleeping bags, in photo- or thermochromic clothing by embedding dyes in the interior of the tube or as identifiers by markers in the interior of the tube.
  • the invention is explained in more detail by the following figures and examples, without being restricted to these embodiments.
  • FIG. 1A a template is shown, on the top of which there is liquid polymer. It can be seen in FIG. 1B that the polymer liquid has wetted the walls of the pores.
  • FIG. 1C shows the state in which the polymer liquid completely fills the pores. The state shown in Figure 1 c occurs when the liquid material has had too much time to penetrate the pores.
  • FIG. 2 shows graphically at which lattice constants of highly ordered pore structures which pore diameters are accessible.
  • the lattice constant is plotted on the X axis and the pore diameter on the Y axis.
  • FIG. 3a A porous template made of silicon is shown in FIG. 3a, the pores being arranged hexagonally.
  • Figure 3b shows a section through such a porous template.
  • FIG. 3c shows macroporous silicon, the main pores of which have defect pores.
  • FIG. 4 shows a template made of macroporous silicon (pore diameter 700 nm, pore length 100 ⁇ m), which was filled with polymethyl methacrylate (PMMA 40,000 D).
  • Figure 4a shows a larger area
  • Figure 4b shows a single pore. It can clearly be seen that the polymer has wetted the pore walls with a film a few tens of nanometers thick.
  • FIG. 5b and FIG. 5c each show an enlarged view of the ends of the top four parallel hollow fibers.
  • the hollow fibers from FIGS. 5a to 5c are made from the template shown in FIG. 3b porous silicon.
  • FIG. 5d shows hollow fibers made of the same material, which were obtained using a commercially available template made of aluminum oxide (Whatman Anopore, diameter of approx. 200 nm, depth of 50 ⁇ m).
  • the aspect ratio of the hollow fibers reproduces that of the template pores and is 250.
  • the aluminum oxide template (Whatman Anopore) had pores with a diameter of approx. 200 nm and a depth of 50 ⁇ m.
  • the aspect ratio of the hollow fibers is 250.
  • FIG. 7b fibers can be seen on the left and right edge of the image, which were produced from regions of the template in which the pore arrangement was irregular.
  • the regular hexagonal arrangement of the template is largely reproduced in the central area.
  • 7c and 7d show details.
  • FIGS. 8b-d show an arrangement of hollow fibers with a bimodal diameter distribution, which was obtained by using the template shown in FIG. 8a made of silicon with larger defect pores, after the selective removal of the template.
  • FIG. 9a shows a breaking edge with PVDF hollow fibers embedded in a template that has not yet been removed.
  • Figure 9b shows a cut PVDF hollow fiber.
  • FIG. 10 shows hollow fibers made of PMMA (80,000 D) / PS (500,000 D) 5: 1, which were obtained by dropping a solution in dichloromethane onto macroporous silicon. The top of the fibers is open (a), the bottom is closed (b).
  • Figure 1 1 shows porous hollow fibers made of polystyrene with a molecular weight of 500,000 D after the selective removal of the template. These were obtained by dropping a 2.4% polystyrene solution in dichloromethane onto an aluminum oxide membrane (Whatman Anodise, diameter approx. 200 nm, pore depth 50 ⁇ m).
  • FIG. 12 shows polymer hollow fibers after the selective removal of the template. These were obtained by dropping a mixture of 83% PMMA (80,000 D) and 17% polystyrene (150,000 D) dissolved in dichloromethane onto macroporous silicon, as shown in FIG. 3c. By imaging the defect pores that emanate from the main pores, hollow fibers with a rough or studded surface were obtained.
  • PMMA 80,000 D
  • polystyrene 150,000 D
  • FIG. 13 shows hollow fibers which are obtained by dropping a solution of polystyrene (8,000 D): polymethyl methacrylate (3,400 D) 7: 3 onto a template rotating at 3,000 rpm (aluminum oxide Whatman Anodise, pore diameter approx. 200 nm, pore depth 50 ⁇ m) were. The template was then selectively removed.
  • polystyrene 8,000 D
  • polymethyl methacrylate (3,400 D) 7 3
  • the template was then selectively removed.
  • Figures 14a-d show hollow fibers of PMMA (80,000 D) / PS (500,000 D) 5: 1, which were obtained by dropping a solution in dichloromethane on macroporous silicon under the action of ultrasound after the selective removal of the template. These hollow fibers have pores or undulations in the wall thickness.
  • Figure 15 shows trough-shaped residual fibers made of PMMA (800,000 D). These were obtained by dropping a homogeneous solution of polyethylene oxide (900,000 D) / PMMA (800,000 D) 5: 1 in dichloromethane onto an aluminum oxide membrane (Whatman Anodise, pore diameter approx. 200 nm, pore depth 50 ⁇ m). The filled template was at 23 h
  • FIG. 16 shows scanning electron micrographs of polytetrafluoroethylene nanotubes. An arrangement of hollow PTFE fibers is shown in FIG. 16a.
  • FIG. 16b shows a cross section along the tube axis of a PTFE fiber.
  • FIG. 17a shows a transmission electron micrograph of a polystyrene / palladium composite fiber, taken with an acceleration voltage of 1 MeV.
  • FIG. 17b shows an energy-dispersive X-ray microanalysis of a single composite fiber on a silicon substrate, it being possible to detect palladium.
  • FIG. 17c shows electron diffraction patterns of a single composite fiber which originate from palladium crystals, the size of which was estimated to be 2 nm by the Debye-Scherrer method.
  • FIG. 17a shows a transmission electron micrograph of a polystyrene / palladium composite fiber, taken with an acceleration voltage of 1 MeV.
  • FIG. 17b shows an energy-dispersive X-ray microanalysis of a single composite fiber on a silicon substrate, it being possible to detect palladium.
  • FIG. 17c shows electron diffraction patterns of a single composite fiber which originate from palladium crystals, the size of which was estimated to be 2 nm by the Deby
  • 17d shows an SEM image of a composite fiber that was treated with ultrasound for 30 min, so that part of the outer Pd layer was removed and the morphology of the composite fiber, consisting of an inner PS layer (dark area of the nanotube on the left in the image) and an outer Pd layer (light area on the right in the picture).
  • FIG. 18 shows scanning electron micrographs of palladium nanotubes with different morphologies, which are obtained by wetting the pores of an aluminum oxide template with a mixture of palladium acetate,
  • FIG. 18a shows an array of Pd nanotubes.
  • FIG. 18b shows Pd nanotubes with a rough, mesh-like and a smooth porous morphology
  • FIGS. 18c and 18d show cross sections through Pd nanotubes.
  • FIG. 19 shows polyether ether ketone (PEEK) nanotubes.
  • FIG. 19a shows an arrangement of PEEK nanotubes, while FIG. 19b shows a single PEEK nanotube with an opening.
  • PEEK polyether ether ketone
  • a pattern was applied to an n-type silicon wafer with a ⁇ 100> orientation using standard photolithography. Alkaline etching produced reverse-pyramidal holes on the surface, which serve as the starting pores. The wafer was then etched with hydrofluoric acid under anodic conditions and back exposure. The electronic holes created by the back exposure in the area of the back surface spread through the entire wafer and cause the silicon to dissolve at the tips of the reverse pyramidal holes.
  • a template was obtained which has pores with a diameter of 700 nm and a pore length of 100 ⁇ m.
  • Example 2 Coating the pore walls of macroporous silicon with polymethyl methacrylate (PMMA)
  • a template made of macroporous silicon (pore diameter 700 nm, pore length 100 ⁇ m) was cleaned for cleaning with nitric acid for 24 hours, then washed twice with deionized water and once with acetone and heated in a heating block at 200 ° C. in vacuo for 2 hours.
  • a vacuum was again applied and the polymer was kept in the liquid state at 200 ° C. for 60 minutes before quenching to room temperature at a cooling rate of 8 K / s.
  • the filled template obtained was examined by scanning electron microscopy.
  • the template produced according to Example 2 with PMMA-coated pore inner walls is shown in FIG. 4.
  • Example 3 Production of polystyrene (PS) hollow fibers by introducing polystyrene melts
  • Porous aluminum oxide templates (Whatman Anopore, diameter of approx. 200 nm, depth of 50 ⁇ m) were treated with deionized water, ethanol, acetone, chloroform and hexane in an ultrasonic bath.
  • Porous silicon templates (pore diameter 370 nm, pore depth 40 ⁇ m) were treated with nitric acid for several days and then washed with deionized water and acetone. The cleaned templates were heated on a heating block in a vacuum to a temperature of 200 ° C. and baked at this temperature for 2 h. Polystyrene powder was added to the top of the heated template.
  • the polymer was applied under argon as a protective gas.
  • the cell with heating block and templates was again placed under vacuum.
  • the temperature was chosen at 200 ° C so that the glass transition temperature of the polystyrene used was significantly exceeded and the liquid polymers could penetrate the pores.
  • the heating block with the template was quenched to room temperature within 20 s. To remove the template, it was treated with an aqueous potassium hydroxide solution.
  • Example 4 Production of polymethyl methacrylate (PMMA) hollow fibers by introducing PMMA melts
  • the templates were cleaned and baked out as described in Example 3.
  • PMMA powder was added to the top of the heated template under an argon protective gas.
  • the cell was again placed under vacuum with a heating block and templates.
  • the temperature was chosen at 200 ° C so that the glass transition temperature of the PMMA used was significantly exceeded and the liquid polymer could penetrate the pores.
  • the heating block with the template was quenched to room temperature within 20 s. To remove the template, it was treated with an aqueous potassium hydroxide solution.
  • PMMA hollow fibers with a wall thickness that varied from about 15 nm to 60 nm depending on the sample were obtained both with templates made of silicon and from aluminum oxide. The shape of the pores was reproduced exactly.
  • the nanotubes obtained were examined with a scanning electron microscope (SEM).
  • Example 4a PMMA hollow fibers were obtained by using a commercially available alumina template with an aspect ratio of 250.
  • a monodomain consisting of PMMA hollow fibers could be obtained, which reproduces the hexagonal arrangement of the pores in the template.
  • Example 4c Template used, which had defect pores that have a significantly larger pore diameter than the majority of pores. After dissolving the template, it became clear that the hollow fibers simulated both the normal pores and the defect pores with their outer diameter. It follows from this that the method according to the invention can be used to produce hollow fibers with an external shape which corresponds to the shape of the pores of the template.
  • the hollow fibers made of PMMA produced according to Example 4a are in FIG. 6, the hollow fibers made of PMMA produced according to Example 4b are shown in FIGS the hollow fibers made of PMMA produced according to Example 4c are shown in FIG. 8.
  • PVDF polyvinylidene fluoride
  • a template filled as described above was cooled in the heating block in a vacuum to 1 30 ° C. and annealed at this temperature for 1 h.
  • X-ray experiments showed that the polymer was partially crystalline and the crystallites were oriented.
  • the lamellar crystals were parallel or the individual chains in the lamellar crystals were arranged perpendicular to the pore wall. This could be concluded from the fact that only the 200 reflex was visible in the diffractogram, i.e. only the 200 network level contributed to the spread.
  • Example 6 Production of hollow fibers from a polymer mixture which are closed on one side and open on one side
  • a homogeneous solution of a mixture of 83% by weight of PMMA and 17% by weight of PS in dichloromethane was dripped onto a macroporous silicon template which, as shown in FIG. 3b, had pocket pores.
  • the liquid material solidified by evaporating the solvent.
  • the template was examined with the scanning electron microscope once from the side on which the pores of the template were closed and once from the opposite side on which the pores of the template were open.
  • the hollow fibers produced according to Example 6 are shown in FIG. 10.
  • Example 8 Production of hollow fibers with a rough surface
  • a homogeneous solution of a mixture of 83% by weight of PMMA and 17% by weight of PS in dichloromethane was dripped onto a macroporous silicon template which, as shown in FIG. 3c, had main pores, the lateral surfaces of which had defect pores.
  • the liquid material solidified by evaporating the solvent.
  • the template was removed selectively with aqueous potassium hydroxide solution.
  • the arrangement of hollow fibers obtained had hollow fibers, the lateral surfaces of which had structures with dimensions in the range of 100 nm, which were created by imaging the defect pores.
  • the hollow fibers were examined with a scanning electron microscope.
  • the hollow fibers produced according to Example 8 are shown in Figure 1 2.
  • Example 9 Production of hollow fibers by introducing the liquid material into a rotating template
  • Example 10 Production of hollow fibers by dropping polymer solutions under the influence of ultrasound
  • a homogeneous solution of a mixture of 83% by weight of PMMA and 17% by weight of PS in dichloromethane was dripped onto a macroporous silicon template (diameter of the pores 470 nm, pore length 50 ⁇ m), the template being ' in an ultrasonic bath Sonorex TK52H was.
  • the liquid material solidified by evaporating the solvent. Ultrasound was applied to the template during the dripping and for the following 5 minutes.
  • the template was removed selectively with aqueous potassium hydroxide solution.
  • the hollow fibers obtained were examined with a scanning electron microscope (SEM). They have periodic undulations of the wall thickness, recognizable from the contrast fluctuations in the SEM images or periodically occurring pores with diameters in the range of 100 nm.
  • SEM scanning electron microscope
  • Example 1 1 Production of hollow fibers with areas of different material composition and selective removal of one of these areas
  • the filled template was annealed at 200 ° C., that is above the solidification temperature of the components, in a heating block for 23 hours and then quenched to room temperature at a rate of 1,50 ° C./min. A segregation process and maturation processes of the segregation morphology occurred during this procedure.
  • the template was removed by treatment with aqueous potassium hydroxide solution. The fibers were then washed twice with water. During this procedure, the water-soluble PEO was completely dissolved. Channel-shaped continuous PMMA residual fibers were obtained, which with a Scanning electron microscope (SEM) were examined.
  • SEM Scanning electron microscope
  • Example 12 Production of hollow fibers from polytetrafluoroethylene
  • Porous aluminum oxide templates with a pore diameter of 460 nm and a pore depth of 40 ⁇ m were treated with deionized water, ethanol, acetone, chloroform and hexane in an ultrasonic bath.
  • the cleaned templates were heated in a heating block in vacuo to a temperature of 350 ° C. and baked at this temperature for 2 h.
  • Polytetrafluoroethylene powder was added to the top of the heated template.
  • the polytetrafluoroethylene was obtained from Aldrich and, according to the manufacturer, had a melting point of 321 ° C. In order to avoid chemical destruction of the polymer, the polymer was introduced under argon as a protective gas.
  • Example 13 Production of polystyrene hollow fibers with a molecular weight of 800,000 D.
  • Porous aluminum oxide templates with a pore diameter of 460 nm and a pore depth of 40 ⁇ m were treated with deionized water, ethanol, acetone, chloroform and hexane in an ultrasonic bath.
  • the cleaned templates were heated in a heating block in a vacuum to a temperature of 235 ° C. and baked at this temperature for 2 hours.
  • Polystyrene powder was added to the top of the heated template.
  • the cell was again placed under a vacuum using a heating block and templates.
  • the temperature was selected at 235 ° C so that the glass transition temperature of the polystyrene used was significantly exceeded and it could penetrate the pores.
  • the heating block with the template was quenched to room temperature within 20 s.
  • To remove the template it was treated with an aqueous potassium hydroxide solution.
  • Polystyrene hollow fibers with a wall thickness of about 30 nm were obtained, each of which reproduced exactly the shape of the pores.
  • the nanotubes obtained were examined with a scanning electron microscope (SEM).
  • the method according to the invention can be used for the functionalization of hollow fibers.
  • the production of palladium / polymer composite hollow fibers, which are important for catalysis or hydrogen storage, is described here by way of example.
  • a silicon template (pore diameter 900 nm) was wetted at room temperature with a solution which contained equal parts by weight of poly-L-lactide (PLLA) and palladium-II-acetate in dichloromethane as the solvent. After evaporation of the solvent, a PLLA / palladium-II acetate film covered the pore walls.
  • the template was then treated at 300 ° C. in vacuo. Under these conditions, PLLA is completely broken down and palladium is converted into the metallic state.
  • FIG. 7a shows a transmission electron micrograph of a Pd / PS composite fiber.
  • the outer cladding is formed by palladium crystallites with a domain size of a few nanometers.
  • Energy dispersive X-ray microanalysis (EDX) of individual composite fibers confirmed the presence of Pd ( Figure 1 7b).
  • the K ⁇ and K ß peaks of C as well as the L and L B peaks of Pd and a signal from the silicon substrate to which the composite fibers were applied for the investigation could also be detected.
  • the method according to the invention can be used for the production of arrays of metal-coated microcavities and of metal nanotubes.
  • the templates are wetted with a mixture of a metal precursor and a selectively removable polymer, an advantageous embodiment using a solvent as the carrier material.
  • a fine phase morphology can be generated by spinodal segregation.
  • the metal precursor is converted into the metal and the polymer is removed.
  • porous aluminum oxide templates are described as an example. These were cleaned as described in Example 3. A solution of polylactide and palladium acetate in dichloromethane was dripped onto the template. Evaporation of the dichloromethane first induced spinodal segregation, then the material solidified. The template was then heated in vacuo at temperatures up to 350 ° C for 1 h. The polylactide and the acetate were removed completely pyrolytically and the palladium, which was originally in the oxidation state + 2, was converted into metallic palladium. The result was a hybrid material in which the pore walls of the porous aluminum oxide were coated with palladium nanoparticles.
  • FIGS. 1 8c and 1 8d Transmission electron microscopy, energy-dispersive X-ray microanalysis and electron diffraction revealed that the tubes were made of metallic palladium.
  • a macroporous silicon template was wetted at 380 ° C. with poly (oxy-1,4-phenyleneoxy-1,4-phenylenecarbonyl-1,4-phenylene), a polyether ether ketone (PEEK). After cooling, the template was selectively removed to give PEEK nanotubes as shown in Figures 19a and 19b.
  • PEEK polyether ether ketone
  • the present invention provides a generally applicable method for producing hollow fibers, in particular in the form of ordered polymer hollow fiber arrangements.
  • the hollow fibers can be made with any polymer system that can be processed in the liquid state (e.g. as a melt or solution).
  • the production of hollow fibers by wetting porous templates with polymer-containing liquids can therefore be used for the production of hollow fibers for a wide range of applications in nanotechnology.

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Abstract

L'invention concerne un procédé de production de fibres creuses, en particulier pour produire des mésotubes et des nanotubes dont les tubes ou fibres creuses présentent un diamètre interne de l'ordre du nanomètre voire du micromètre et sont de préférence orienté(e)s dans une direction. Cette invention se rapporte en outre à l'utilisation desdites fibres creuses, aux fibres creuses ou tubes produit(e)s au moyen dudit procédé ainsi qu'aux matériaux composites poreux les contenant.
EP03743870A 2002-03-11 2003-03-11 Procede de production de fibres creuses Withdrawn EP1485526A1 (fr)

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US7297305B2 (en) 2004-04-08 2007-11-20 Research Triangle Institute Electrospinning in a controlled gaseous environment
DE102004053373A1 (de) * 2004-11-02 2006-05-04 Justus-Liebig-Universität Giessen Erfindung betreffend anisometrische Partikel in Form von Nano-/Meso-Fasern -Röhren, -Kabeln -Bändern und deren gekrümmte oder verzweigte Abwandlungen
DE102006035189B4 (de) * 2006-07-29 2011-06-22 Fachhochschule Kaiserslautern, 66482 Flächige Struktur, Vlies, Gewirk, Gewebe, Abstandsgewebe, Wärme- oder Schalldämmung sowie Hohlfaser zum Transport von Wärmeenergie
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