Chemically resistant fluorinated multiblock polymer structures, methods of manufacturing and use

Abstract

Multi-block isoporous structures for non-aqueous and/or harsh chemical media having at least one of high separation specificity, chemical resistance, and antifouling properties, methods of manufacturing and use, for replacements or alternatives to existing separation membrane technologies.

Description

FIELD OF THE INVENTION

The invention relates to multi-block isoporous structures resistant to non-aqueous and/or harsh chemical media, where the structures have at least one of high flux, high separation specificity, chemical resistance, and antifouling properties, and methods of manufacturing and use, as replacements or alternative to existing separation membrane technologies.

BACKGROUND OF THE INVENTION

Membranes have been manufactured to be resistant to chemicals, heat, and radiation, by reacting fluorine containing monomers, e.g., tetrafluoroethylene, vinylidene fluoride to produce polytetrafluoroethylene (PTFE) or poly(vinylidene fluoride), which are hydrophilic or by providing a hydrophilic fluorine surface. These fluorine containing polymers are not isoporous, not produced by self-assembly, and do not self-assemble. Block copolymers containing fluorinated blocks have been used to create dense ion-conducting membranes, for liquid/liquid separations, or in gas/gas separations. Similarly, these fluorinated block copolymers are non-isoporous, and lack the pore tuning properties associated with self-assembled polymers and flow characteristics.

Fluoropolymer membranes are described in U.S. Pat. No. 5,130,024, where PTFE membranes are coated with hydrophilic fluorine containing copolymers on pores. Other examples of surface modified membrane are described in U.S. Pat. No. 5,928,792, where the porous membrane surface is modified with perfluorocarbon copolymer, and U.S. Pat. No. 6,354,443 where the membrane surface is coated with hydrophilic fluorinated copolymers.

In addition, fluorine-containing graft copolymers and adhesive composed essentially of the copolymer and a composite membrane of a support and the copolymer are taught in U.S. Pat. No. 4,666,991. In the U.S. Pat. No. 4,666,991, a fluorinated polymer is grafted to another polymer. Whereas other prior art techniques involve applying a fluorinated graft copolymer to existing membranes physically, e.g., dip coating, spin coating, etc.

Hollow fiber, porous membranes, with layers formed from polyethylene, polypropylene, poly (4-methylpentene-1), poly (vinylidene fluoride) or polyoxymethylene, are disclosed in U.S. Pat. No. 6,379,796. The porous layers are interposed with layers of a homogeneous thin film. The homogeneous film can include two material, where the first material is a polymer blend composed of a styrene-based thermoplastic elastomer and a polyolefin. Where the styrene-based thermoplastic elastomer and be “A block copolymer in which the hard segments comprise a styrene polymer and the soft segments comprise a polymer derived from at least one monomer selected from butadiene, ethylene-butylene isoprene and ethylene-propylene” or “A random copolymer composed of two or more types of constitutional units formed from styrene and at least one of butadiene, ethylene-butylene, isoprene and ethylene-propylene,” none of which includes a fluorinated component. The second material disclosed in the patent is a copolymer of (2, 2-bistrifluoromethyl-4, 5-difluoro-1, 3-dioxole) and tetrafluoroethylene, but is not a block copolymer.

Copolymers of fluorinated polydienes and sulfonated polystyrenes are disclosed in U.S. Pat. No. 7,619,036, where the block copolymers include sulfonated polystyrene blocks A along with fluorinated blocks B, having the general diblock structure AB, and triblock structure ABA.

Existing fluorinated porous membranes that contain block copolymer components include a coating of a fluorine-containing polymer/copolymer. In addition, some chemistries in these block copolymer have undesirable fouling characteristics (e.g. undesirable physical and chemical interactions) with components of the feed stream.

However, as described, the predominant technique for surface modification involves providing a coating of a fluorine containing material, which coated product can have imperfections, such as pin-holes in the coating, or be susceptible to separation or delamination. In addition, isoporous block copolymer membranes are typically formed from vinyl-derived polymers that are soluble or unstable in many organic solvents. These features typically limit their use of vinyl-derived polymers to aqueous solutions and thus their overall utility. Thus, a need exists for chemically resistant isoporous structures without the drawbacks and limitations of existing polymer membranes (e.g., chemically resistant without needing a coating), chemically resistant to harsh chemical materials, (e.g., organic materials, inorganic and organic acids and bases), and provides a structure that self-assembles to provide a pore tunable structure that is suitable for separation processes involving organic materials, inorganic and organic acids and bases.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 (A) is a schematic of an isoporous portion of material (10).

FIG. 1 (B) is a schematic of fluorinated (20) portions of an isoporous portion of material (20) formed directly from a fluorinated copolymer.

FIG. 1 (C) is a schematic of an isoporous portion of material (10) undergoing a chemical reaction (30) to fluorinate the isoporous material, yielding fluorinated (20) material.

SUMMARY OF THE INVENTION

Multiblock copolymers of the invention achieve self-assembled isoporous structures that permit high flux contemporaneously with solvent-resistance. The materials allow for multi-functionality of the isoporous materials, wherein at least one block can impart significant chemical resistance (if fluorinated, for example) while the other blocks provide other functionalities, e.g. mechanical integrity. These materials are particularly useful as chemically resistant and antifouling membranes for separations.

In the context of the invention, isoporous means having a substantially narrow pore diameter distribution. In the context of the invention, mesopores are defined as having a diameter of about 1 nm to about 200 nm. The isopores may also be mesoporous.

The invention relates to isoporous fluorinated block copolymer structures where at least one of the blocks is chemically modified to impart antifouling and/or chemical resistance properties to harsh solvent conditions from organic, acidic or basic materials, and other blocks provide mechanical integrity to the structure, to enhance its suitability for various environments. In an approach, at least one block is fluorinated prior to polymerization with other blocks. In an alternative approach, the multiblock polymer is chemically modified after the formation of the multiblock polymer.

The multiblock isoporous structures are of particular use for stocks comprising non-aqueous and/or harsh chemical media having at least one of high separation specificity, chemical resistance, and antifouling properties as replacements or alternatives to existing separation membrane technologies.

The present invention relates to block copolymer structures where at least one of the blocks is chemically fluorinated to impart chemical resistance to harsh solvent conditions from organic, acidic or basic materials.

The present invention relates to fluorinated polymer material with at least two distinct polymer blocks, wherein at least one of the blocks contains at least one of macro, meso, or micro pores, at least some of which are isoporous, wherein at least a portion of at least one polymer block is fluorinated. The mesopores are of about 1-200 nm in size and macropores are at least 200 nm or greater in size. The material is asymmetric or symmetric. The material contains at least one of macroporous domains and mesoporous domains. The block copolymer may comprise fluorinated portions either before or after isoporous material formation, or any combination of fluorination before or after isoporous material formation.

The present invention provides methods of preparing fluorinated polymer material with at least two distinct polymer blocks, by forming an isoporous structure of a multiblock copolymer, and then fluorinating at least a portion of at least one unfluorinated block with a post functionalization reaction.

The present invention provides methods where the isoporous material is formed by dissolving a polymer in at least one chemical solvent; dispensing a polymer solution onto a substrate or mold, or through a die or template; removing at least a portion of chemical solvent during which at least a portion of the polymer self-assembles; exposing the self-assembled material to a nonsolvent causing precipitation of at least a portion of the polymer; and optionally, washing the treated material.

The invention also includes a process of maintaining the integrity of an isoporous block polymer structures by chemically modifying at least one of the blocks with a fluorochemical moiety, and then forming an isoporous multiblock polymer structure.

The invention also includes separating an analyte of interest with high permeability and excellent selectivity, the membrane has uniform porosity, by contacting a non-aqueous liquid containing an analyte of interest with an isoporous fluorinated block polymer structures with at least two distinct polymer blocks.

One or more polymer blocks, or the overall polymer or polymers, may comprise complex polymer architectures, so long as the block copolymer self-assembles to generate the isoporous material. In this context, a “complex” block structure or polymer architecture signifies more than one monomer, chemistry, configuration, or structure in at least one block, or adjacent to blocks. A combination of different block copolymer starting materials is another complex architecture.

The invention also includes separating an analyte of interest with high permeability and excellent selectivity from a harsh chemical mixture generated by organic, acidic or basic liquids and the analyte of interest, by contacting the mixture with an isoporous fluorinated block polymer structure.

DETAILED DESCRIPTION OF THE INVENTION

The invention is an isoporous structure, e.g., a membrane, film, fabric, monolith, which comprises at least one multiblock polymer where at least one block comprises at least a portion that contains fluorine atoms (“fluorinated”). The incorporation of fluorine atoms imparts chemical resistance and antifouling properties to the isoporous block copolymer structure. This combination of fluorinated polymer blocks in a multiblock copolymer (e.g. A-B, A-B-C, A-B-C-D, or A-B-C-D-E) structure, produced by self-assembly, results in a high permeability and high selectivity isoporous structure for separations in non-aqueous liquid media, e.g., organic or harsh liquid media. Additionally, the fluorination adds antifouling behavior to the material.

Table 1 below provides non-limiting examples of block copolymer architectures.

Different letters denote different chemistries, where A, B, C, D and E are respectively polymer blocks formed from the same monomer, and -co- indicates a mixture of chemistries in a specific block. The distribution of mixtures of chemistries may be periodic (ordered), random/statistical, or graded within the block.

TABLE 1
                    Formula
[A]-[B]             I
[A]-[B]-[C]         II
[A]-[B]-[C-co-D]    III
[A-co-B]-[C]-[D]    IV
[A-co-B]-[C-co-D]   V
[A]-[B]-[C]-[D]     VI
[A]-[B]-[C]-[D]-[E] VII

As shown in Table 1, at least two distinct polymer blocks are present. At least one of the blocks contains at least one of macro, meso, or micro pores, at least some of which are isoporous, wherein at least a portion of at least one polymer block is fluorinated.

Mesopores may be in the range of about 1 nm to about 200 nm. In an embodiment, the mesopores are in the range of 1 nm to 200 nm. In an embodiment, the mesopores are in the range of 3 nm to 200 nm. In an embodiment, the mesopores are in the range of 5 nm to 200 nm. In an embodiment, the mesopores are in the range of 5 nm to 100 nm. In an embodiment, the mesopores are in the range of 10 nm to 100 nm.

The fluorinated isoporous structures are asymmetric, symmetric, partially symmetric or partially asymmetric.

The fluorinated isoporous structures are supported by a porous support or are unsupported. The fluorinated isoporous structures are in the form of two-dimensional (e.g. films, flat sheets) or three-dimensional (e.g. monoliths, beads, hollow fibers, tubular) structures.

The fluorinated isoporous structures are suitable as a separation media, and/or as a fabric with desirable protective properties (e.g. clothing, bandages). In the liquid-based separation application, the liquids being exposed to the fluorinated isoporous structures are not limited to purely aqueous solutions. The chemical stability imparted to the fluorinated isoporous structures from the fluorination allows solutions contacting the membrane to contain in part, or completely, non-aqueous liquids, as well as aqueous solutions that may otherwise degrade, decompose, or dissolve nonfluorinated structures. The harsh media in which the fluorinated isoporous structure may be used include, for example, highly acidic solutions, highly basic solutions, petrochemical products, organic solvents, and other organic small molecules. The fluorination of the block copolymers also imparts further heat resistance to the membranes, allowing operation at elevated temperatures.

The fluorinated isoporous structures may be achieved through several different approaches. In some approaches, at least a portion of the isoporous material is fluorinated before the formation of the isoporous structure. In some approaches, at least a portion of the isoporous material is fluorinated after the formation of the isoporous structure. In one approach, the structures are achieved by incorporating fluorinated monomer as at least a portion of the monomer feed, polymerizing the monomers to form a multiblock fluorinated polymer, and then forming an isoporous structure. In another approach, the structures are achieved by incorporating fluorinated monomer as at least a portion of the monomer feed, polymerizing the monomers to form a multiblock fluorinated copolymer, and then forming an isoporous structure, then fluorinating at least a portion of an unfluorinated block with a post functionalization reaction. In another approach, the structures are achieved by forming an isoporous structure from a multiblock copolymer, then fluorinating at least a portion of at least one unfluorinated block with a post functionalization reaction. In another approach, the structures are achieved by fluorinating at least a portion of at least one unfluorinated block of a block copolymer and then forming an isoporous structure.

In an approach, fluorine atoms are incorporated into at least a portion of at least one block of the copolymer which is used to fabricate the structure, by first fluorinating the monomer, and then polymerizing the fluorinated block with the other polymer blocks. Another approach is modifying at least a portion of at least one block of a multiblock polymer to be fluorinated, then forming the isoporous structure. Yet another approach is modifying an already fabricated isoporous structure to incorporate fluorine atoms into at least a portion of at least one block of the copolymer comprising the membrane.

The multiblock polymer must at least partially self-assemble when processed from a deposition solution comprising the multiblock polymer and a solvent system. During the process, at least a portion of the solvent system is removed; then, the material is exposed to a phase separation solvent system, such that at least a portion of the polymer material precipitates.

Suitable, non-limiting examples of fluorinated and unfluorinated polymer blocks include the following:

The invention also comprises separating and/or detecting and/or isolating an analyte of interest, comprising contacting an organic material and analyte containing fluid with the multiblock fluorinated isoporous polymer structure to obtain or detect the analyte of interest.

The multiblock polymer structures incorporate fluorine atoms through direct polymerization of fluorinated monomer and/or post-polymerization chemical functionalization, either before or after isoporous structure formation. Suitable fluorinated monomers/block chemistries include, but are not limited to, perfluorinated C3-C6 linear and cyclic compounds, fluorinated compounds such as, but not limited to, octafluoropropane (perfluoropropane), decafluorobutane (perfluorobutane), dodecafluoropentane (perfluoropentane), tetradecafluorohexane (perfluorohexane), dodecafluorocyclohexane (perfluorocyclohexane); fluorinated C6-C9 aromatic compounds; fluorinated acrylics such as, but not limited to, 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl acrylate, 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,12-heneicosafluorododecyl acrylate, 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl methacrylate, 2,2,3,3,4,4,4-heptafluorobutyl acrylate, 2,2,3,3,4,4,4-heptafluorobutyl methacrylate, 2,2,3,4,4,4-hexafluorobutyl acrylate, 2,2,3,4,4,4-hexafluorobutyl methacrylate, 1,1,1,3,3,3-hexafluoroisopropyl acrylate, 1,1,1,3,3,3-hexafluoroisopropyl methacrylate, 2,2,3,3,4,4,5,5-octafluoropentyl acrylate, 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate, 2,2,3,3,3-pentafluoropropyl acrylate, 2,2,3,3,3-pentafluoropropyl methacrylate, 1H,1H,2H,2H-perfluorodecyl acrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl acrylate, 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl methacrylate, 2,2,2-trifluoroethyl methacrylate, 1,1,1-trifluoro-2-(trifluoromethyl)-2-hydroxy-4-methyl-5-pentyl methacrylate, 2-[(1′,1′,1′-trifluoro-2′-(trifluoromethyl)-2′-hydroxy)propyl]-3-norbornyl methacrylate; fluorostyrenes such as, but not limited to 2-fluorostyrene, 3-fluorostyrene, 4-flourostyrene, 2,3,4,5,6-pentafluorostyrene; other fluorine containing monomers such as, but not limited to epifluorohydrin, glycidyl 2,2,3,3,4,4,5,5-octafluoropentyl ether, glycidyl 2,2,3,3-tetrafluoropropyl ether, perfluorohexylethylene, 3,3,4,4,5,5,6,6,6-nonafluoro-1-hexene, 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluoro-1-decene, and (2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-heptadecafluorononyl)oxirane.

Mixtures of chemistries within a single block are denoted with “-co-” and two structures bound by a single set of brackets, as shown in Table 1, above. The distribution of mixed chemistries in a block may be periodic (ordered), random/statistical, or graded within the block.

In some embodiments, the material is packaged as a device including: a pleated pack, flat sheets in a crossflow cassette, a spiral wound module, hollow fiber, a hollow fiber module, or as a sensor. In an embodiment, a device utilizes more than one different isoporous fluorinated material.

In one embodiment, the material or device comprising the material has a detectable response to a stimulus/stimuli.

In some embodiments, the material, or a device comprising the material, is used in a process wherein an analyte of interest is separated in a medium containing the analyte of interest contacting the material or device. In one such process, the analyte of interest is separated by binding and eluting. In another such process, solutes or suspended particles are separated by filtration. In another such process, both bind and elute and separation by filtration mechanisms are incorporated.

In some embodiments, the material, or a device comprising the material, is used in a process wherein an analyte of interest is detected in a medium containing the analyte of interest contacting the material or device. In one such process, the analyte of interest is detected by a response of the material/device to the presence of the analyte of interest.

In some embodiments, at least two different material are packaged together as a kit. In other embodiments, at least two devices comprising the material are packaged together as a kit.

In some embodiments, the material is immobilized to or integrated with a support or a textile.

A method for achieving the invention involves: dissolution of a block copolymer in at least one chemical solvent; dispensing the polymer solution onto a substrate or mold, or through a die or template; removal of at least a portion of the chemical solvent; exposure to a nonsolvent causing precipitation of at least a portion of the polymer, and optionally, a wash step.

Non-limiting examples of fluorination of polymer blocks after polymerization are provided below.

As shown above, step “A)” is the fluorination of poly(4-vinylpyridine) with 1,1,1,2,2,3,3,-heptafluoro-5-iodopentane wherein upon heating, the iodine on the 1,1,1,2,2,3,3,-heptafluoro-5-iodopentane is a leaving group for attachment to the nitrogen on the poly(4-vinlypyridine), resulting in a quaternized pyridine and fluorinated poly(4-vinylpyridine) block. Step “B)” is the fluorination of cis-1, 4 poly(isoprene) wherein upon heating 2,2,3-trifluoro-3-(trifluoromethyl)oxirane reacts to fluorinate the double bond of the poly(isoprene). In step “C)” the fluorination of 3, 4-poly (isoprene) in two steps: first, a hydroboration/oxidation reaction to introduce a hydroxyl group off the poly(isoprene) double bond, then an esterification reaction with heptafluorobutanoyl chloride wherein the chloride on heptafluorobutanoyl chloride is a leaving group, resulting the fluorinated poly(isoprene).

The first approach for producing the isoporous structures is the direct polymerization of fluorinated monomer units into the block copolymer. This is achieved with a partial or complete fraction of fluorine-containing monomer units polymerized directly in the polymer block(s). This approach directly incorporates the fluorinated atoms through chemical bonding into the polymer which is subsequently processed into the isoporous material. Another similar approach is initiating or terminating the polymerization with a fluorinated molecule or macromolecule to fluorinate the copolymer with a single unit.

Another approach is chemically modifying a block copolymer not containing fluorinated units to include fluorine atoms in at least one block. This fluorine-modified (fluorinated) copolymer is subsequently processed into the fluorinated isoporous material. The fluorinated units are introduced by reaction to the multiblock polymer with a compound, such as, but not limited to, fluorine-containing compounds wherein the compound contains another halide such as bromine, chlorine, or iodine which serves as a leaving group for attachment to the polymer (e.g. 1,1,1,2,2,3,3-heptafluoro-5-iodopentane, 1,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8-heptadecafluoro-10-iododecane perfluoropropyliodide, heptafluorobutanoyl chloride); fluorine; hexafluoropropylene oxide; sulfur tetrafluoride; difluorocarbene; trifluoroacetic anhydride; and difluoroacetic anhydride.

A still further approach for the fabrication of the isoporous material is post-modifying isoporous block copolymer materials to incorporate fluorine atoms. One such approach is the chemical modification of isoporous material to include fluorine atoms. This method involves directly chemically modifying the isoporous material, such that surfaces of the polymer block, including pore surfaces are modified. The aforementioned compounds are also suitable for this approach.

Combinations of these approaches are also used to achieve the isoporous material. For example, fluorinated monomer is polymerized to fluorinate one block of the copolymer, and subsequently another unfluorinated block is post-fluorinated.

The amount of fluorination and chemistry of the fluorinated material is controllable. This is controlled through varying the amount of fluorinated reagents relative to unfluorinated material during either polymerization or post-functionalization.

One variant is partially or completely fluorinating units of more than one block of the constituent copolymer. Which block(s) is/are fluorinated is not limited to the block that comprises the structure's major surface. Crosslinking with a fluorinated compound is another approach to imparting chemical resistance to membranes, through a combination of cross-linking and fluorination.

The pore size of the isoporous region of the membrane is also controllable. The pore size can be varied from ˜1-200 nm.

Isoporous block copolymer membranes incorporating fluorination in/on at least a portion of at least one block of the block copolymer. This imparts chemical resistance and antifouling properties to the membranes.

The polymers may be synthesized in any manner with the proviso that the polymer can self-assemble and form the isoporous material through the described methods.

Table of features identified in Figures 1(A)-1(C)
10 Isoporous portion of material
20 Fluorinated portion of material
30 Reaction to introduce fluorination to material

Claims

1. A multiblock isoporous fluorinated polymer material comprising at least two distinct polymer blocks, wherein a first of said distinct polymer blocks is a fluorinated block having a structure:

2. The material of claim 1 wherein the multiblock fluorinated polymer material is asymmetric.

3. The material of claim 1, wherein the mesopores have a size of about 1-200 nm.

4. The material of claim 1 wherein the material is formed into a two-dimensional structure.

5. The material of claim 1 wherein the material is formed into a three-dimensional structure.

6. The material of claim 1 wherein the material is made by a process comprising: a. polymerizing a multiblock polymer comprising 3,4-poly(isoprene) blocks; andb. fluorination of the 3,4-poly(isoprene) blocks via introduction of a hydroxyl group on a double bond of the 3,4-poly(isoprene) followed by esterification with heptafluorobutanoyl chloride to produce the multiblock fluorinated polymer.

7. The material of claim 6, wherein the fluorination of the 3, 4-poly (isoprene) blocks is performed before the formation of the isoporous structure.

8. The material of claim 1 wherein the material does not degrade, decompose, or dissolve when exposed to acidic solutions, basic solutions, petrochemical products, organic solvents, or other organic small molecules.

9. The material of claim 1 wherein the material does not degrade, decompose, or dissolve at elevated temperatures relative to room temperature.

10. A process separating or detecting an analyte of interest, the method comprising contacting a medium containing the analyte of interest with the material of claim 1.