Abstract: A separator including a porous substrate and a porous layer. The porous layer is disposed on a surface of the porous substrate and includes inorganic particles and a binder. The porous substrate has an absolute plastic deformation rate in a first direction ranging from about 40% to about 1800%. By using the separator provided in the present application, the safety performance of lithium ion batteries is improved.

Abstract: The present invention relates to a method for determining the logarithmic reduction value LRV of a size-exclusion filter for a particle of a process solution, which particle is to be clarified, the size-exclusion filter being protected from a blocking adsorbing species present in the process solution by a process adsorber which is connected upstream in series.

Abstract: A film having high heat resistance and a low total haze value and yellowness index. The film includes a fluorinated polyimide layer having a total haze value of 4 or lower, a yellowness index of 3 or lower, and a total luminous transmittance of 90% or higher.

Abstract: A radiation curable composition for preparing a polymeric membrane includes a) a membrane polymer selected from the group consisting of a polysulfone (PSU), a polyether sulfone (PES), a polyether etherketone (PEEK), a polyvinylchloride (PVC), a polyacrylonitrile (PAN), a polyvinylidene fluoride (PVDF), a polyimide (PI), a polyamide (PA) and copolymers thereof; b) a hydrophobic monomer or oligomer having at least two free radical polymerizable groups independently selected from the group consisting of an acrylate group, a methacrylate group, an acrylamide group, a methacrylamide group, a styrene group, a vinyl ether group, a vinyl ester group, a maleate group, a fumarate group, an itaconate group, and a maleimide group; and c) an organic solvent for the membrane polymer and the hydrophobic monomer. A polymeric membrane and a method for manufacturing the membrane are also disclosed.

Abstract: Provided are a polyimide and/or polyamideimide porous body and method for manufacturing same, method for separation and/or adsorption using the porous body, a separation material, adsorption material, and filter media composed of the porous body, a laminate, and a filter device. A polyimide and/or polyamideimide porous body in which the polyimide and/or polyamideimide has at least one group selected from the group consisting of a carboxy group, a salt-type carboxy group, and a —NH— bond.

Abstract: Microporous polyamide-imide membranes and methods for making them are disclosed. The microporous membrane includes polyamide-imide polymer, wherein the membrane has an HFE bubble point, and an IPA flow-time. The microporous membrane has an HFE bubble point from about 25 psi to about 200 psi and has an IPA flow-time from about 400 second to about 40,000 seconds. Another microporous polyamide-imide membrane includes a polyamide-imide polymer, wherein the membrane has a HFE bubble point from about 25 psi to about 200 psi. The membrane is asymmetric—and has a tight layer with a thickness of <10 microns. Filter and purification devices incorporating such devices are also disclosed.

Abstract: The present invention provides a porous hollow fiber membrane that has both high strength and high pure water permeability, and that exhibits excellent thermal deformation resistance. The present invention is related to a porous hollow fiber membrane containing a fluororesin-based polymer, and a manufacturing method of the membrane comprises a drawing step and a relaxing step. The porous hollow fiber membrane is characterized in that: the molecular chain of the polymer is oriented in the longitudinal direction of the hollow fiber membrane; and at the same time internal distortion of oriented non-crystalline chains, which is disadvantageous in terms of entropy, is alleviated.

Abstract: A process for separating a feed gas comprising polar and non-polar gases into a gas mixture enriched in polar gas(es) and a gas mixture depleted in polar gas(es), the process comprising passing the feed gas through a gas separation unit comprising at least two gas-separation modules in order of increasing selectivity for the polar gas(es), wherein the feed gas entering the gas separation unit comprises more than 35 mol % and up to 90 mol % of polar gas(es).

Abstract: A process for separating a feed gas comprising polar and non-polar gases into a gas mixture enriched in polar gas(es) and a gas mixture depleted in polar gas(es), the process comprising passing the feed gas through a gas separation unit comprising at least two gas-separation modules in order of decreasing selectivity for the polar gas(es), wherein the feed gas entering the gas separation unit comprises 1 to 35 mol % of polar gas(es).

Abstract: The present invention provides high permeance copolyimide membranes and methods for making and using these membranes for gas separations such as for hydrogen purification and for acid gas removal from natural gas. The random copolyimide polymers used to make the copolyimide membrane may be UV crosslinked to improve selectivity in separating mixtures of gases or in purifying liquids. The membranes may be fabricated into any known membrane configuration such as a flat sheet or a hollow fiber.

Abstract: Hydrophilic porous membranes comprising a random copolymer of: (a) 2-hydroxyethyl methacrylate of formula (I): (b) an ethylene glycol dimethacrylate of formula (II): and (c) 1,1,1-trimethylolpropane trimethacrylate of formula (III): and a hydrophobic polymer; filters including the membranes, and methods of making and using the membranes, are disclosed.

Abstract: A gas separation composite membrane, containing a gas-permeable supporting layer and a gas separating layer containing a crosslinked polyimide resin over the gas-permeable supporting layer, in which the crosslinked polyimide resin is formed by a polyimide compound being crosslinked by a radically crosslinkable functional group thereof, and a ratio [?] of a crosslinked site to an imide group of the polyimide compound (the number of crosslinked sites/the number of imide groups) in the crosslinked polyimide resin is 0.0001 or more and 0.45 or less; a method of producing the same; and a gas separating module, a gas separation apparatus and a gas separation method using the same.

Abstract: A hollow fiber membrane made of two coextruded layers A and B, wherein layer B has a non-woven type structure having a mesh size of 0.1 to 10 ?m and layer A has a porous structure. A method for producing a membrane according to the invention and the use thereof is also disclosed.

Abstract: The invention provides a graphene derivative composite membrane and method for fabricating the same. The graphene derivative composite membrane comprises a support membrane made of porous polymer and a plurality of graphene derivative layers disposed on the support membrane wherein the distance between adjacent graphene derivative layers is about 0.3˜1.5 nm and the total thickness of the plurality of graphene derivative layers is more than 100 nm.

Abstract: Described herein are mixed matrix filtration membranes and related, compositions, methods and systems and in particular mixed matrix filtration membranes with an embedded polymer network and/or embedded polymeric micro/nanoparticles functionalized with a functionalization polymer covalently and/or non covalently linked to the micro/nanoparticles and related compositions, methods, and systems.

Abstract: The present invention discloses a blends of an aromatic polyimide polymer and a polymer containing aromatic sulfonic acid groups that can be converted into polybenzoxazole (PBO) membranes for gas, vapor, and liquid separations. The PBO membranes that were prepared by thermal treating aromatic polyimide membranes containing between 0.05 and 20 wt-% of a poly(styrene sulfonic acid) polymer. These polymers showed up to 95% improvement in selectivity for CO2/CH4 and H2/CH4 separations compared to PBO membranes prepared from corresponding aromatic polyimide membranes without a poly(styrene sulfonic acid) polymer.

Abstract: The present invention discloses a novel method to improve the selectivities of polybenzoxazole (PBO) membranes prepared from aromatic polyimide membranes for gas, vapor, and liquid separations. The PBO membranes that were prepared by thermal treating aromatic polyimide membranes containing between 0.05 and 20 wt-% of a poly(styrene sulfonic acid) polymer. These polymers showed up to 95% improvement in selectivity for CO2/CH4 and H2/CH4 separations compared to PBO membranes prepared from corresponding aromatic polyimide membranes without a poly(styrene sulfonic acid) polymer.

Abstract: Improved integrally skinned asymmetric membranes for organic solvent nanofiltration, and their methods of preparation and use are disclosed. Membranes are formed from polyimides by phase inversion and are then crosslinked by addition of amine crosslinking agents that react with the imide groups of the polyimide, creating amide bonds. These stabilize the membranes and allow solvent nanofiltration to be maintained even in the solvents from which the membranes were formed by phase inversion.

Abstract: The invention provides a novel type of filter media that offers efficient disinfection effects, while achieving a low water pressure drop and a high water flow rate when in use. Specifically, the filter media of the invention comprises a microorganism-killing membrane containing electro spun nanofiber fabrics loaded with biocidal nano-particles. The filter media of the invention is adhesive-layer free and contains at least one thermal binding layer that are made of spunbonded nonwoven polymeric fabrics. The invention also provides a water-purification cartridge and a portable water system thereof.

Abstract: Embodiments of a filter device utilize a membrane comprising poly(amic) acid. The membrane has a porous structure with pores configured to filter nano-sized particles, e.g., less than 100 nm. In one embodiment, the filter device can comprises a substrate (e.g., filter paper) and the membrane disposed on the substrate. This configuration is useful to capture, isolate, and detect nano-particles.

Abstract: The disclosure provides a filtration material and a method for fabricating the same. The filtration material includes a supporting layer, and a composite layer, wherein the composite layer includes an ionic polymer and an interfacial polymer. Particularly, the ionic polymer and the interfacial polymer are intertwined with each other, resulting from ionic bonds formed between the ionic polymer and the interfacial polymer.

Abstract: Method for preparing a filtration membrane and a filtration membrane prepared by the method. According to one embodiment, the method involves casting a polymer solution onto a porous support to form a coated support. The coated support is then quenched to form a membrane/support composite, and the membrane/support composite is then dried. Next, a first end of a first piece of adhesive tape is applied to the membrane side of the composite, and the second end of the first piece of adhesive tape is applied to a first rotatable winder. In addition, a first end of a second piece of adhesive tape is applied to the support side of the composite, and the second end of the second piece of adhesive tape is applied to a second rotatable winder. The two winders are then rotated so as to pull apart the membrane from the support.

Abstract: Technologies are generally described for composite membranes which may include a porous graphene layer in contact with a porous support substrate. In various examples, a surface of the porous support substrate may include at least one of: a thermo-formed polymer characterized by a glass transition temperature, a woven fibrous membrane, and/or a nonwoven fibrous membrane. Examples of the composite membranes permit the use of highly porous woven or nonwoven fibrous support membranes instead of intermediate porous membrane supports. In several examples, the composite membranes may include porous graphene layers directly laminated onto the fibrous membranes via the thermo-formed polymers. The described composite membranes may be useful for separations, for example, of gases, liquids and solutions.

Abstract: The present invention generally relates to gas separation membranes and, in particular, to high selectivity fluorinated ethylene-propylene polymer-comprising polymeric blend membranes for gas separations. The polymeric blend membrane comprises a fluorinated ethylene-propylene polymer and a second polymer different from the fluorinated ethylene-propylene polymer. The fluorinated ethylene-propylene polymers in the current invention are copolymers comprising 10 to 99 mol % 2,3,3,3-tetrafluoropropene-based structural units and 1 to 90 mol % vinylidene fluoride-based structural units. The second polymer different from the fluorinated ethylene-propylene polymer is selected from a low cost, easily processable glassy polymer.

Abstract: The present invention is directed to microfiltration and ultrafiltration membranes comprising a microporous material. The microporous material comprises: (a) a polyolefin matrix present in an amount of at least 2 percent by weight, (b) finely divided, particulate, substantially water-insoluble silica filler distributed throughout said matrix, said filler constituting from about 10 percent to about 90 percent by weight of said coated microporous material substrate, (c) at least 20 percent by volume of a network of interconnecting pores communicating throughout the coated microporous material, and (d) at least one coating composition applied to at least one surface of the membrane to adjust the surface energy of the membrane.

Abstract: The present disclosure describes an additive that may be used in the manufacture of thin-film polyamide composite membranes. Thin-film polyamide composite membranes are used in filtration processes, such as reverse osmosis and nanofiltration. The additive may be an amino-siloxane compound. The amino-siloxane compound includes repeated groups of silicon bonded to oxygen with at least one amine functional group. Optionally, the amino-siloxane compound may also include a hydrophilic group. The additive reacts with an aqueous phase and an organic phase to form a thin polyamide film on a porous substrate.

Abstract: A hydrophilic semipermeable hollow-fiber membrane for blood treatment, with an integrally asymmetric structure based on a synthetic polymer. The hollow-fiber membrane possesses on its inner surface a separating layer and an adjoining open-pored supporting layer, and has an ultrafiltration rate in albumin solution of 5 to 25 ml/(h·m2·mmHg). The hollow-fiber membrane is free from pore-stabilizing additives and has a maximum sieving coefficient for albumin of 0.005 and a sieving coefficient for cytochrome c that satisfies the equation SCCC?5·10?5·UFRAlb3?0.004·UFRAlb2+1.081·UFRAlb?0.25.

Abstract: The present invention discloses a new type of high performance polymer membranes derived from aromatic polyimide membranes and methods for making and using these membranes. The polymer membranes described in the present invention were derived from aromatic polyimide membranes by crosslinking followed by thermal treating. The aromatic polyimide membranes were made from aromatic polyimide polymers comprising both pendent hydroxy functional groups ortho to the heterocyclic imide nitrogen and cross-linkable functional groups in the polymer backbone. The high performance polymer membranes showed significantly improved permeability for gas separations compared to the aromatic polyimide membranes without any treatment. The high performance polymer membranes also showed significantly improved selectivity for gas separations compared to the thermal-treated but non-UV-crosslinked aromatic polyimide membranes.

Abstract: The present disclosure describes a method for forming microporous membranes. More specifically, vapor induced phase separation techniques are used for forming multizone microporous membranes having improved material throughput.

Abstract: An electrochemical separation membrane and the manufacturing method thereof are disclosed. The method includes: a polymer solution preparing step to mix a polymer material, solvent and ceramic precursors thoroughly to form a polymer solution, wherein the polymer material and the ceramic precursors are dissolved uniformly in the solvent; a coating step to coat the polymer solution on a porous base material; a hydrolysis step to cause the porous base material coated with the polymer solution to contact an aqueous solution to hydrolyze the ceramic precursor into ceramic particles; and a drying step to remove the water and the solvent from the porous base material and in order to form the electrochemical separation membrane. The electrochemical separation membrane made of this method have better ion conductivity, interface stability and thermal stability based on the ceramic particles.

Abstract: The present invention discloses blend polymer membranes comprising thermally rearranged polymers derived from aromatic polyimides containing ortho-positioned functional groups and methods for making and using these blend polymer membranes. The blend polymer membranes described in the current invention are prepared by heat treatment of blend polymer membranes comprising aromatic polyimides containing ortho-positioned functional groups such as —OH or —SH groups. In some instances, an additional crosslinking step is performed to improve the selectivity of the membrane. These blend polymer membranes have improved flexibility, reduced cost, improved processability, and enhanced selectivity and/or permeability compared to the comparable polymer membranes that comprise a single polymer.

Abstract: Provided is a composite semipermeable membrane, comprising: a microporous support membrane which comprises a substrate and a porous support, and a polyamide separation functional layer formed on the microporous support membrane, wherein the polyamide has an irreversible heat absorption, which is measured using temperature modulated DSC, of 275 J/g or more at a temperature in the range of ?20 to 150° C. in the first heating process. Provided is a high-performance composite semipermeable membrane having high chemical durability, high water permeation and high rejection.

Abstract: A separation membrane is provided containing hydrophilic molecules and having, as formed on at least one surface of a feed side and a permeate side thereof, a height difference of from 80 ?m to 2000 ?m, in which a weight of the hydrophilic molecules in a bone-dry separation membrane is from 0.1% to 40% based on a weight of the bone-dry separation membrane from which the weight of the hydrophilic molecules has been subtracted.

Abstract: The invention relates to a process for membrane separation that makes it possible to separate linear hydrocarbons from branched hydrocarbons. The membrane that is used comprises a dense selective layer that consists of a polymer whose chemical structure contains at least one bis-phenyl-9,9-fluorene group.

Abstract: The present invention relates to a membrane being suitable for, for example, hemodialysis. Said membrane comprises at least one hydrophobic polymer and at least one hydrophilic polymer. According to the present invention the outer surface of the hollow fiber has pores in the range of 0.5-3 ?m and the numbers of said pores in the outer surface are in the range of 10,000 to 150,000 pores per mm2, preferably in the range of 18,000 to 100,000 pores per mm2, and most preferably in the range of 20,000 to 100,000 pores per mm2. The present invention further relates to a process for the preparation of said membrane and use of said membrane in hemodialysis, hemodiafiltration and hemofiltration, and in dialysis and filtration in general, for example in water purification or dehydration.

Abstract: The present invention discloses high performance polybenzoxazole membranes prepared from aromatic poly(o-hydroxy amide) membranes by thermal cyclization and a method for using these membranes. The polybenzoxazole membranes were prepared by thermal treating aromatic poly(o-hydroxy amide) membranes in a temperature range of 200° to 550° C. under inert atmosphere. The aromatic poly(o-hydroxy amide) membranes used for making the polybenzoxazole membranes were prepared from aromatic poly(o-hydroxy amide) polymers comprising pendent phenolic hydroxyl groups ortho to the amide nitrogen in the polymer backbone. In some embodiments of the invention, the polybenzoxazole membranes may be subjected to an additional crosslinking step to increase the selectivity of the membranes.

Abstract: In one aspect, the invention relates to engineered osmosis and related membrane-based separation technologies. Disclosed are semi-permeable nanostructured osmosis membranes comprising a film polymerized on a nanofiber support fabric, methods for osmotically-driven separation, the method comprising creating an osmotic pressure gradient across a semi-permeable nanostructured osmosis membrane comprising a film polymerized on a nanofiber support fabric, and methods of generating power comprising creating an osmotic pressure gradient across a semi-permeable nanostructured osmosis membrane comprising a film polymerized on a nanofiber support fabric. This abstract is intended as a scanning tool for purposes of searching in the particular art and is not intended to be limiting of the present invention.

Abstract: Described herein are thin film composite (TFC) membranes, for use in forward osmosis (FO) and pressure reduced osmosis (PRO) processes. The membrane is comprised of two layers: a composite layer combining a backing layer and a porous, polymer-based support into a single layer, and a rejection layer disposed on top of the composite layer. The membrane of the invention exhibits high water flux values for FO processes, is durable, may be readily manufactured using typical membrane manufacturing processes, such as spiral winding and plate and frame processes, and has sufficient mechanical stability to handle the final membrane product.

Abstract: The present invention involves the use of a multi-stage membrane system for gas, vapor, and liquid separations. In this multi-stage membrane system, high selectivity and high permeance or at least high selectivity polybenzoxazole membranes or cross-linked polybenzoxazole membranes are applied for a pre-membrane or both the pre-membrane and the secondary membrane. A primary membrane can be from conventional glassy polymers. This multi-stage membrane system can reduce inter-stage compression cost, increase product recovery and product purity for gas, vapor, and liquid separations. It can also save the cost compared to the system using all the high cost polybenzoxazole membranes or cross-linked polybenzoxazole membranes.

Abstract: The present invention is directed to thin film composite membrane (TFC membrane) comprising a substrate layer (S) based on a sulfonated polymer, e.g. a sulfonated polyarylether, and a polyamide film layer (F) and further to a method for their preparation. Furthermore, the present invention is directed to osmosis processes, in particular to forward osmosis (FO) processes, using said membrane.

Abstract: Solvent and acid stable ultrafiltration and nanofiltration membranes including a non-cross-linked base polymer having reactive pendant moieties, the base polymer being modified by forming a cross-linked skin onto a surface thereof, the skin being formed by a cross-linking reaction of reactive pendant moieties on the surface with an oligomer or another polymer as well as methods of manufacture and use thereof, including, inter alia separating metal ions from liquid process streams.

Abstract: The present invention discloses a new type of high performance polymer membranes prepared from aromatic polyimide membranes by thermal treating and crosslinking and methods for making and using these membranes. The polymer membranes were prepared from aromatic polyimide membranes by thermal treating under inert atmosphere followed by crosslinking preferably by using a UV radiation source. The aromatic polyimide membranes were made from aromatic polyimide polymers comprising both pendent hydroxy functional groups ortho to the heterocyclic imide nitrogen and cross-linkable functional groups in the polymer backbone. The membranes showed significantly improved selectivity and permeability for gas separations compared to the aromatic polyimide membranes without any treatment. The membranes can be fabricated into any convenient geometry and are not only suitable for a variety of liquid, gas, and vapor separations, but also can be used for other applications such as for catalysis and fuel cell applications.

Abstract: The present invention involves the use of a multi-stage membrane system for gas, vapor, and liquid separations. In this multi-stage membrane system, high selectivity and high permeance or at least high selectivity polybenzoxazole membranes or cross-linked polybenzoxazole membranes are applied for a pre-membrane or both the pre-membrane and the secondary membrane. A primary membrane can be from conventional glassy polymers. This multi-stage membrane system can reduce inter-stage compression cost, increase product recovery and product purity for gas, vapor, and liquid separations. It can also save the cost compared to the system using all the high cost polybenzoxazole membranes or cross-linked polybenzoxazole membranes.

Abstract: A thermally, heat and chemically stable polyimide asymmetric ultrafiltration membrane, is a porous film or a hollow fiber, having an anisotropic structure a selective surface layer and a substrate, wherein the selective ultraporous surface layer has size of pores 70-800 ? with thickness 0.1-10 mcm and is composed of insoluble rigid-chain aromatic (co)polyimide based on dianhydride of aromatic tetracarbonic acid and aromatic diamine and located on the microporous substrate with thickness 50-250 mcm, and the membrane has water permeability Q=(2?500)·10?4 cm/sec atm and nominal molecular weight cutoff ML=(5?500)·103 g/mol, and method for producing an ultrafiltration membrane as disclosed.

Abstract: The present invention the manufacture of a membrane for gas and liquid separations in which a polymer layer is applied directly to a tricot fabric instead of the conventional cloth or glass or metal substrate.

Abstract: The present invention discloses new types of polybenzoxazole-based mixed matrix membranes and methods for making and using these membranes. The polybenzoxazole-based mixed matrix membranes are prepared by fabricating a polyimide-based mixed matrix membrane by dispersing molecular sieve particles in a continuous aromatic polyimide matrix with pendent hydroxyl groups ortho to the heterocyclic imide nitrogen; and then converting the polyimide-based mixed matrix membrane to a polybenzoxazole-based mixed matrix membrane by heating between 200° and 600° C. under inert atmosphere or vacuum. The polybenzoxazole-based mixed matrix membranes of the present invention can be fabricated into any convenient geometry such as flat sheet (or spiral wound), tube, hollow fiber, or thin film composite.

Abstract: The present invention discloses a new type of high performance polymer membranes prepared from aromatic polyimide membranes by thermal treating and crosslinking and methods for making and using these membranes. The polymer membranes were prepared from aromatic polyimide membranes by thermal treating under inert atmosphere followed by crosslinking preferably by using a UV radiation source. The aromatic polyimide membranes were made from aromatic polyimide polymers comprising both pendent hydroxy functional groups ortho to the heterocyclic imide nitrogen and cross-linkable functional groups in the polymer backbone. The membranes showed significantly improved selectivity and permeability for gas separations compared to the aromatic polyimide membranes without any treatment. The membranes can be fabricated into any convenient geometry and are not only suitable for a variety of liquid, gas, and vapor separations, but also can be used for other applications such as for catalysis and fuel cell applications.

Abstract: A process for the extraction of hydrogen from a gas mixture including hydrogen and carbon monoxide and optionally nitrogen, carbon dioxide, lower hydrocarbons and/or water, by contacting the gas mixture with a non-porous polyimide-based membrane, especially with the selective side of an asymmetric membrane, to obtain a hydrogen rich permeate and a hydrogen lean retenate, the polyimide-based membrane being a specific mixture of two polyimids. This specific membrane shows a very high hydrogen/carbon monoxide selectivity. The process is especially suitable for the upgrading of synthesis gas obtained by partial oxidation and/or reforming of hydrocarbonaceous feedstream for use in hydrocarbon synthesis reaction as the Fischer-Tropsch reaction.

Abstract: In the present invention high performance cross-linked polybenzoxazole and polybenzothiazole polymer membranes and methods for making and using these membranes have been developed. The cross-linked polybenzoxazole and polybenzothiazole polymer membranes are prepared by: 1) first synthesizing polyimide polymers comprising pendent functional groups (e.g., —OH or —SH) ortho to the heterocyclic imide nitrogen and cross-linkable functional groups in the polymer backbone; 2) fabricating polyimide membranes from these polymers; 3) converting the polyimide membranes to polybenzoxazole or polybenzothiazole membranes by heating under inert atmosphere such as nitrogen or vacuum; and 4) finally converting the membranes to high performance cross-linked polybenzoxazole or polybenzothiazole membranes by a crosslinking treatment, preferably UV radiation. The membranes can be fabricated into any convenient geometry.

Abstract: In the present invention high performance cross-linked polybenzoxazole and polybenzothiazole polymer membranes and methods for making and using these membranes have been developed. The cross-linked polybenzoxazole and polybenzothiazole polymer membranes are prepared by: 1) first synthesizing polyimide polymers comprising pendent functional groups (e.g., —OH or —SH) ortho to the heterocyclic imide nitrogen and cross-linkable functional groups in the polymer backbone; 2) fabricating polyimide membranes from these polymers; 3) converting the polyimide membranes to polybenzoxazole or polybenzothiazole membranes by heating under inert atmosphere such as nitrogen or vacuum; and 4) finally converting the membranes to high performance cross-linked polybenzoxazole or polybenzothiazole membranes by a crosslinking treatment, preferably UV radiation. The membranes can be fabricated into any convenient geometry.