Multilayer composite membranes and methods of using same

Abstract

The present disclosure provides composite membranes including a porous substrate, a gutter layer, and a separation layer. The gutter layer is located between the porous substrate and the separation layer. Methods of separating gases are also provided.

Description

[0001] PA104065W002

[0002] MULTILAYER COMPOSITE MEMBRANES AND METHODS OF USING SAME

[0003] Background

[0004] Separation membranes are known; however, there is a continual need for effective composite membranes.

[0005] Summary

[0006] In a first aspect, a composite membrane is provided. The composite membrane comprises a porous substrate, a gutter layer, and a separation layer. The gutter layer includes a segmented polydiorganosiloxane copolymer. The gutter layer is disposed between the porous substrate and the separation layer.

[0007] In a second aspect, a method of separating gases is provided. The method comprises passing a mixture of gases through a composite membrane according to any embodiment of the first aspect, in which the passing operation comprises passing the mixture of gases through the separation layer prior to the gutter layer.

[0008] The above summary of the present disclosure is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The description that follows more particularly exemplifies illustrative embodiments. In several places throughout the application, guidance is provided through lists of examples, which examples may be used in various combinations. In each instance, the recited list serves only as a representative group and should not be interpreted as an exclusive list.

[0009] Brief Description of the Drawings

[0010] FIG. 1 is a schematic cross-sectional view of an exemplary composite membrane according to the present disclosure;

[0011] FIG. 2 is a schematic cross-sectional view of another exemplary composite membrane according to the present disclosure including various optional layers; and

[0012] FIG. 3 is a schematic cross-sectional view of results of the peel experiment for Example 1.

[0013] FIG. 4 is a plot of intensity versus scattering vector for two different polyorganosiloxane materials, as determined by small angle x-ray scattering.

[0014] FIG. 5 is a plot of intensity versus scattering vector for twelve different polyorganosiloxane materials, as determined by small angle x-ray scattering.

[0015] While the above-identified figures set forth various embodiments of the disclosure, other embodiments are also contemplated, as noted in the description. In all cases, this disclosure presents embodiments of the invention by way of representation and not limitation. The figures are not necessarily to scale. Like numbers used in the figures refer to like components. However, it will be understood that the use of a number to refer to a component in a given figure is not intended to limit the component in another figure labeled with the same number.

[0016] Detailed Description

[0017] Glossary:

[0018] The term “length” refers to the longest dimension of an object.

[0019] The term “layer” refers to a material that has a substantially larger length and width than height (e.g., substantially larger in the x-y plane than the z-plane).

[0020] The term “thickness” refers to the smallest dimension of a film or layer, e.g., in a z-axis while a major surface of the film or layer is in the x- and y-axes.

[0021] The term “porous substrate” refers to a support material that may include one or more layers and a plurality of pores.

[0022] The term “gutter layer” refers to a layer that is present on a major surface of a porous substrate and functions to channel gases towards pores of the porous substrate.

[0023] The term “separation layer” refers to a layer that functions to selectively separate at least two gases from each other.

[0024] The term “interfacial layer” refers to a layer that forms a common boundary between two other layers.

[0025] The term “protection layer” refers to a layer that functions to shield at least one other layer from damage.

[0026] The term “alkyl” refers to a monovalent group that is a radical of an alkane, which is a saturated hydrocarbon. The alkyl can be linear, branched, cyclic, or combinations thereof and typically has 1 to 20 carbon atoms. In some embodiments, the alkyl group contains 1 to 18, 1 to 12, 1 to 10, 1 to 8, 1 to 6, or 1 to 4 carbon atoms. Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, ethylhexyl, n- dodecyl, 2-dodecyl, 3-dodecyl, 4-dodecyl, and 5-dodecyl.

[0027] The term “alkylene” is the multivalent (e.g., divalent or trivalent) form of the “alkyl” groups defined above.

[0028] The term “alkenyl” refers to a monovalent group that is a radical of an alkene, which is a hydrocarbon with at least one carbon-carbon double bond. The alkenyl can be linear, branched, cyclic, or combinations thereof and typically contains 2 to 20 carbon atoms. In some embodiments, the alkenyl contains 2 to 18, 2 to 12, 2 to 10, 4 to 10, 4 to 8, 2 to 8, 2 to 6, or 2 to 4 carbon atoms. Exemplary alkenyl groups include ethenyl, n-propenyl, and n-butenyl.

[0029] The term “alkoxy” refers to a monovalent group of formula -OR where R is an alkyl group.

[0030] The term “alkoxycarbonyl” refers to a monovalent group of formula -(CO)OR where R is an alkyl group and (CO) denotes a carbonyl group with the carbon attached to the oxygen with a double bond. The term “aralkyl” refers to a monovalent group of formula -Ra-Ar where Rais an alkylene and

[0031] Ar is an aryl group. That is, the aralkyl is an alkyl substituted with an aryl.

[0032] The term “aralkylene” refers to a divalent group of formula -Ra-Ar'- where Rais an alkylene and Ar3is an arylene (i.e., an alkylene is bonded to an arylene).

[0033] The term “aryl” refers to a monovalent group that is aromatic and carbocyclic. The aryl can have one to five rings that are connected to or fused to the aromatic ring. The other ring structures can be aromatic, non-aromatic, or combinations thereof. Examples of aryl groups include, but are not limited to, phenyl, biphenyl, terphenyl, anthryl, naphthyl, acenaphthyl, anthraquinonyl, phenanthryl, anthracenyl, pyrenyl, perylenyl, and fluorenyl.

[0034] The term “arylene” refers to a divalent group that is carbocyclic and aromatic. The group has one to five rings that are connected, fused, or combinations thereof. The other rings can be aromatic, non- aromatic, or combinations thereof. In some embodiments, the arylene group has up to 5 rings, up to 4 rings, up to 3 rings, up to 2 rings, or one aromatic ring. For example, the arylene group can be phenylene.

[0035] The term “aryloxy” refers to a monovalent group of formula -OAr where Ar is an aryl group.

[0036] The term “carbonyl” refers to a divalent group of formula -(CO)- where the carbon atom is attached to the oxygen atom with a double bond.

[0037] The term “ether” refers to a divalent group of formula -R-O-R-, where R is independently a hydrocarbon group.

[0038] The term “amide” refers to a monovalent group with a nitrogen atom bonded to a carbonyl carbon atom.

[0039] The term “halo” refers to fluoro, chloro, bromo, or iodo.

[0040] The term “haloalky 1” refers to an alkyl having at least one hydrogen atom replaced with a halo. Some haloalkyl groups are fluoroalkyl groups, chloroalkyl groups, or bromoalkyl groups.

[0041] The term “heteroalkylene” refers to a divalent group that includes at least two alkylene groups connected by a thio, oxy, or -NR- where R is alkyl. The heteroalkylene can be linear, branched, cyclic, or combinations thereof and can include up to 60 carbon atoms and up to 15 heteroatoms. In some embodiments, the heteroalkylene includes up to 50 carbon atoms, up to 40 carbon atoms, up to 30 carbon atoms, up to 20 carbon atoms, or up to 10 carbon atoms. Some heteroalkylenes are polyalkylene oxides where the heteroatom is oxygen.

[0042] The term “oxalyl” refers to a divalent group of formula -(CO)-(CO)- where each (CO) denotes a carbonyl group.

[0043] The term “polydiorganosiloxane” refers to a divalent block or segment of formula: where each R1is independently an alkyl, haloalkyl, aralkyl, alkenyl, aryl, or aryl substituted with an alkyl, alkoxy, or halo; each Y is independently an alkylene, aralkylene, or a combination thereof; and subscript n is independently an integer of 0 to 1500. The term “urea” refers to a divalent block or segment having the general formula — N(H) — C(O)— N(H) — .

[0044] The terms “room temperature” and “ambient temperature” are used interchangeably to mean temperatures in the range of 20°C to 25°C.

[0045] The term “adjacent” as used herein when referring to two layers means that the two layers are in proximity with one another with no intervening open space between them. They may be in direct contact with one another (e.g., coated together) or there may be intervening layers.

[0046] The terms “polymer” and “polymeric material” include, but are not limited to, organic homopolymers, copolymers, such as for example, block, graft, random and alternating copolymers, terpolymers, etc., and blends and modifications thereof. Furthermore, unless otherwise specifically limited, the term “polymer” shall include all possible geometrical configurations of the material. These configurations include, but are not limited to, isotactic, syndiotactic, and atactic symmetries.

[0047] The terms “(co)polymer” or “(co)polymers” includes homopolymers and copolymers, as well as homopolymers or copolymers that may be formed in a miscible blend, e.g., by coextrusion or by reaction, including, e.g., transesterification. The term ''copolymer" includes random, block and star (e.g. dendritic) copolymers.

[0048] The term “semi-crystalline” with respect to a (co)polymer means that the (co)polymer exhibits a crystalline melting temperature as determined using differential scanning calorimetry and is intended to refer to both partially crystalline and fully crystalline (co)polymers.

[0049] As used herein, the term “essentially free” in the context of a composition being essentially free of a component, refers to a composition containing less than 1% by weight (wt.%), 0.5 wt.% or less, 0.25 wt.% or less, 0.1 wt.% or less, 0.05 wt.% or less, 0.001 wt.% or less, or 0.0001 wt.% or less of the component, based on the total weight of the composition.

[0050] The words “preferred” and “preferably” refer to embodiments of the disclosure that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the disclosure.

[0051] In this application, terms such as “a”, “an”, and “the” are not intended to refer to only a singular entity, but include the general class of which a specific example may be used for illustration. The terms “a”, “an”, and “the” are used interchangeably with the term “at least one.” The phrases “at least one of’ and “comprises at least one of’ followed by a list refers to any one of the items in the list and any combination of two or more items in the list.

[0052] As used herein, the term “or” is generally employed in its usual sense including “and / or” unless the content clearly dictates otherwise.

[0053] The term “and / or” means one or all of the listed elements or a combination of any two or more of the listed elements. Also herein, all numbers are assumed to be modified by the term “about” and preferably by the term “exactly.” As used herein in connection with a measured quantity, the term “about” refers to that variation in the measured quantity as would be expected by the skilled artisan making the measurement and exercising a level of care commensurate with the objective of the measurement and the precision of the measuring equipment used. Also herein, the recitations of numerical ranges by endpoints include all numbers subsumed within that range as well as the endpoints (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

[0054] As used herein as a modifier to a property or attribute, the term “generally”, unless otherwise specifically defined, means that the property or attribute would be readily recognizable by a person of ordinary skill but without requiring absolute precision or a perfect match (e.g., within + / - 20 % for quantifiable properties). The term “substantially”, unless otherwise specifically defined, means to a high degree of approximation (e.g., within + / - 10% for quantifiable properties) but again without requiring absolute precision or a perfect match. Terms such as same, equal, uniform, constant, strictly, and the like, are understood to be within the usual tolerances or measuring error applicable to the particular circumstance rather than requiring absolute precision or a perfect match.

[0055] In a first aspect, a composite membrane is provided. The composite membrane comprises: a porous substrate; a gutter layer comprising a segmented polydiorganosiloxane copolymer; and a separation layer, wherein the gutter layer is disposed between the porous substrate and the separation layer.

[0056] Referring to FIG. 1, a schematic cross-sectional view is provided of an exemplary composite membrane 100. The composite membrane 100 includes a porous substrate 110, a gutter layer 120 on at least a portion of a first major surface 111 of the porous substrate 110, and a separation layer 130 on at least a portion of a first major surface 121 of the gutter layer 120. The gutter layer 120 is disposed between the porous substrate 110 and the separation layer 130. In this embodiment, the gutter layer 120 is directly adjacent to the porous substrate 110 and directly adjacent to the separation layer 130.

[0057] Referring to FIG. 2, a schematic cross-sectional view is provided of another exemplary composite membrane 200 that includes several optional layers. The composite membrane 200 includes a porous substrate 110, a gutter layer 120 on at least a portion of a first major surface 111 of the porous substrate 110, and a separation layer 130. The gutter layer 120 is disposed between the porous substrate 110 and the separation layer 130.

[0058] In some cases, a composite membrane contains a surfactant present in at least one of: i) an interfacial layer disposed between the gutter layer and the separation layer; ii) within the separation layer; or iii) within the gutter layer. The composite membrane 200 depicted in FIG. 2 includes an optional interfacial layer 140 disposed between the gutter layer 120 and the separation layer 130. Such an optional interfacial layer may be designed to increase adhesion between the gutter layer and any layer that is directly adjacent to the gutter layer 120. In some cases, an interfacial layer comprises or consists of a surfactant. In the composite membrane 200 depicted in FIG. 2, the separation layer 130 is a first separation layer and the composite membrane 200 further includes an optional second separation layer 132 disposed between the gutter layer 120 and the first separation layer 130. The composite membrane 200 depicted in FIG. 2 further comprises an optional protection layer 150. The optional protection layer 150 is disposed on the first separation layer 130. In this embodiment, the gutter layer 120 is directly adjacent to the porous substrate 110 and directly adjacent to the optional interfacial layer 140.

[0059] It is expressly contemplated that any combination of one or more of the optional layers 132, 140, or 150, may be included in select embodiments of composite membranes according to the present disclosure.

[0060] The exemplary porous substrate 110 that is shown in each of FIGS. 1 and 2 includes three layers that include a nanoporous layer 112, a microporous layer 114, and a macroporous layer 116 having a first major surface 111 and a second major surface 119. It should be understood that a porous substrate suitable for use in the composite membranes of the present disclosure does not require a macroporous layer 116. In select embodiments, a pore size of the nanoporous layer ranges from 10 nanometers (nm) to 100 nm. In a porous substrate 110, the pores are interconnected vertically (i.e., throughout the thickness “T” of the porous substrate 110). In certain preferred embodiments, the pores of the porous substrate 110 are interconnected horizontally (e.g., as in a microfiltration membrane) along dimension “H”.

[0061] It has been discovered that it is possible to form a successful gutter layer from segmented polydiorganosiloxane copolymer. This was unexpected at least because polydiorganosiloxane copolymers tend to be soft, which could lead to significant intrusion into surface pores of a porous substrate on which the segmented polydiorganosiloxane copolymer is deposited. Blocking of pores decreases permeance of a gas through the composite membrane. Composite membranes according to the present disclosure, however, exhibit advantageously high permeance of carbon dioxide, as shown in the Examples below. In some embodiments, the separation layer of a composite membrane is selective for carbon dioxide. For instance, in certain cases, a composite membrane according to the present disclosure exhibits a carbon dioxide gas to nitrogen gas selectivity of at least 20 CO2 / N2, such as at least 25, 30, 35, 40, 45, 50, or even at least 55 CO2 / N2. The maximum selectivity is a material dependent property.

[0062] In certain cases, a composite membrane according to the present disclosure exhibits a carbon dioxide permeance of at least 100 gas permeation units (GPU), such as at least 200, 250, 500, 750, 1000, 1250, 1500, 1750, 2000, 2250. 2500, 2750, 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500, 7000, 7500, 8000, 8500, 9000, or even at least 9500 GPU. In some cases, the carbon dioxide permeance is as high as 10,000 GPU.

[0063] The composite membrane 100 may be suitable for gas separation. Gas separation is a process that involves a membrane in contact with a gas mixture on the feed or upstream side and a separated gas stream on the “permeate” or downstream side. Usually, a feed gas mixture is pressurized, for example, to 5 pounds per square inch (psi), 10 psi, 20 psi, 30 psi, 40 psi, 50 psi or above. Either a vacuum or sweep gas is applied on the downstream side of the membrane to provide a driving force for the process. Preferably, each of the gutter layer 120 and the separation layer 130 is a continuous layer. As used herein, a “continuous layer” refers to a substantially continuous layer as well as a layer that is completely continuous. That is, as used herein, any reference to the gutter layer coating or covering the first major surface of the porous substrate includes the gutter layer coating all, substantially all, or only a portion of the first major surface of the porous substrate. The gutter layer is considered to coat substantially all of the first major surface of the porous substrate (i.e., be substantially continuous) and the separation layer is considered to coat substantially all of the first major surface of the gutter layer, when enough of the first major surface of the porous substrate is coated such that the composite membrane is able to selectively separate a desired amount of a first gas from a mixture of the first gas with a second gas. Gutter layer continuity may be evaluated by gas selectivity of CO2 / N2. A gutter layer coated membrane typically shows a gas selectivity of at least 3, at least 5, at least 7, or at least 9. In particular, the flux and the selectivity of the composite membrane is sufficient for the particular system in which the membrane is used.

[0064] Each of the materials used to form composite membranes are described in detail below.

[0065] Porous Substrates

[0066] Composite membranes according to the present disclosure include a porous substrate.

[0067] The porous substrate itself may be asymmetric or symmetric. The porous substrate may include one layer or multiple layers. For example, there may be two, three, four, or more layers. In some embodiments, the porous substrate is hydrophobic. In other embodiments, the porous substrate is hydrophilic. Preferably, the porous substrate exhibits a nitrogen gas permeance of between 10,000- 500,000 gas permeation units (GPU).

[0068] If the porous substrate is asymmetric, the first and second major surfaces have porous structures with different pore morphologies. For example, the porous substrate may have pores of differing sizes throughout its thickness. Analogously, if the porous substrate is symmetric, the major surfaces have porous structures wherein their pore morphologies are the same. For example, the porous substrate may have pores of the same size throughout its thickness.

[0069] Referring to FIG. 1, an asymmetric substrate is shown with different pore morphologies at the first major surface 111 and the second major surface 119. More specifically, there are three layers each of different pore size such that the overall substrate has pores of differing sizes throughout its thickness “T.” In certain embodiments, the nanoporous layer 112 alone could function as the porous substrate. In such embodiments, the porous substrate would be symmetric.

[0070] Suitable porous substrates include, for example, films, porous membranes, woven webs, nonwoven webs, hollow fibers, and the like. For example, the porous substrates may be made of one or more layers that include films, porous films, micro-filtration membranes, ultrafiltration membranes, nanofiltration membranes, woven materials, and nonwoven materials. The materials that may be used for each of the above-mentioned supports may be organic in nature (such as the organic polymers listed below), inorganic in nature (such as aluminum, steels, and sintered metals and / or ceramics and glasses), or a combination thereof. For example, the porous substrate may be formed from polymeric materials, ceramic and glass materials, metal, and the like, or combinations (i.e., mixtures and copolymers) thereof.

[0071] In composite membranes of the present disclosure, materials having good adhesion to each other are particularly desirable. In certain embodiments, the porous substrate is preferably a polymeric porous substrate.

[0072] Suitable polymeric materials include, for example, polystyrene, polyolefins, polyisoprenes, polybutadienes, fluorinated polymers (e.g., polyvinylidene fluoride (PVDF), ethylene-co- chlorotrifluoroethylene copolymer (ECTFE), polytetrafluoroethylene (PTFE)), polyvinyl chlorides, polyesters (PET), polyamides (e.g., various nylons), polyimides, polyethers, poly(ether sulfone)s, poly(sulfone)s, poly(phenylene sulfone)s, polyphenylene oxides, polyphenylene sulfides (PPS), poly(vinyl acetate)s, copolymers of vinyl acetate, poly(phosphazene)s, poly(vinyl ester)s, poly(vinyl ether)s, poly(vinyl alcohol)s, polycarbonates, polyacrylonitrile, polyethylene terephthalate, cellulose and its derivatives (such as cellulose acetate and cellulose nitrate), and the like, or combinations (i.e., mixtures or copolymers) thereof.

[0073] Suitable polyolefins include, for example, poly(ethylene), poly(propylene), poly(l-butene), copolymers of ethylene and propylene, alpha olefin copolymers (such as copolymers of 1 -butene, 1- hexene, 1-octene, and 1-decene), poly(ethylene-co-l -butene), poly(ethylene-co-l-butene-co-l-hexene), and the like, or combinations (i.e., mixtures or copolymers) thereof.

[0074] Suitable fluorinated polymers include, for example, polyvinylidene fluoride (PVDF), polyvinyl fluoride, copolymers of vinylidene fluoride (such as poly(vinylidene fluoride-co-hexafluoropropylene)), copolymers of chlorotrifluoroethylene (such as ethylene-co-chlorotrifluoroethylene copolymer), polytetrafluoroethylene, and the like, or combinations (i.e., mixtures or copolymers) thereof.

[0075] Suitable polyamides include, for example, poly(imino(l-oxohexamethylene)), poly(iminoadipoylimino hexamethylene), poly(iminoadipoyliminodecamethylene), polycaprolactam, and the like, or combinations thereof.

[0076] Suitable polyimides include, for example, poly(pyromellitimide), polyetherimide, and the like.

[0077] Suitable poly(ether sulfone)s include, for example, poly(diphenylether sulfone), poly(diphenylsulfone-co-diphenylene oxide sulfone), and the like, or combinations thereof.

[0078] Suitable polyethers include, for example, polyetherether ketone (PEEK).

[0079] In some presently preferred embodiments, the porous substrate comprises a polymeric material selected from the group consisting of polyacrylonitrile (PAN), polydimethylsiloxane copolymer (e.g., a copolymer of polydimethylsiloxane / polyurea / polyurethane / polyamide / polyoxalyldiamine), polysulfone, cellulose acetate, polyether sulfone (PES), polyvinylidene fluoride (PVDF), polyetherimide (PEI), polyaminosiloxane, polydimethylphenylene oxide (PPO), polyvinylpyridine (PVP), ethylene chlorotrifluoroethylene (ECTFE), polytetrafluoroethylene (PTFE), polyamide, polyethylene, polypropylene, polymethylpentene, cellulose nitrate, polyester, polycarbonate, and polyimide. Suitable porous substrates may have pores of a wide variety of sizes. For example, suitable porous substrates may include nanoporous membranes, microporous membranes, microporous nonwoven / woven webs, microporous woven webs, microporous fibers, nanofiber webs and the like. In some embodiments, the porous substrate may have a combination of different pore sizes (e.g., micropores, nanopores, and the like). In one embodiment, the porous substrate is microporous.

[0080] In some embodiments, the porous substrate includes pores that may have an average pore size less than 10 micrometers (pm). In other embodiments, the average pore size of the porous substrate may be less than 5 pm, or less than 2 pm, or less than 1 pm. In other embodiments, the average pore size of the porous substrate may be greater than 10 nm (nanometer). In some embodiments, the average pore size of the porous substrate is greater than 50 nm, or greater than 100 nm, or greater than 200 nm. In certain embodiments, the porous substrate includes pores having an average size in the range of from 0.5 nm up to and including 1000 pm. In some embodiments, the porous substrate may have an average pore size in a range of 10 nm to 10 pm, in a range of 50 nm to 5 pm, in a range of 100 nm to 2 pm, in a range of 200 nm to 1 pm, or in a range of 10 nm to 100 nm.

[0081] In certain embodiments, the porous substrate includes a nanoporous layer. In certain embodiments, the nanoporous layer is adjacent to or defines the first major surface of the porous substrate. In certain embodiments, the nanoporous layer includes pores having a size in the range of from 0.5 nanometers (nm) up to and including 100 nm. In accordance with the present disclosure, the size of the pores in the nanoporous layer may include, in increments of 1 nm, any range between 0.5 nm and 100 nm. For example, the size of the pores in the nanoporous layer may be in the range of from 0.5 nm to 50 nm, 1 nm to 25 nm, 2 nm to 10 nm, 10 nm to 100 nm, etc. Molecular Weight Cut-Off (MWCO) is typically used to correlate to the pore size. That is, for nanopores, the molecular weight of a polymer standard (retain over 90%) such as dextran, polyethylene glycol, polyvinyl alcohol, proteins, polystyrene, poly(methyl methacrylate) may be used to characterize the pore size. For example, one supplier of the porous substrates evaluates the pore sizes using a standard test, such as ASTM E1343-90-2001 using polyvinyl alcohol. In select cases, the porous substrate has a first major surface having a) an average pore size of less than 100 nm and b) a porosity of 0.1 to 20 percent.

[0082] In certain embodiments, the porous substrate includes a microporous layer. In certain embodiments, the microporous layer is adjacent to or defines the first major surface of the porous substrate. In certain embodiments, the microporous layer includes pores having a size in the range of from 0.01 pm up to and including 20 pm. In accordance with the present disclosure, the size of the pores in the microporous layer may include, in increments of 0.05 pm, any range between 0.01 pm up and 20 pm. For example, the size of the pores in the microporous layer may be in the range of from 0.05 pm to 10 pm, or 0.1 pm to 5 pm, or 0.2 pm to 1 pm, etc. Typically, the pores in the microporous layer may be measured by mercury porosimetry for average or largest pore size, bubble point pore size measurement for the largest pores, Scanning Electron Microscopy (SEM) and / or Atom Force Microscopy (AFM) for the average / largest pore size. In certain embodiments, the porous substrate includes a macroporous layer. In certain embodiments, the macroporous layer is adjacent to or defines the first major surface of the porous substrate. In certain embodiments, the macroporous layer is embedded between two microporous layers, for example a BLA020 membrane obtained from 3M Purification Inc.

[0083] In certain embodiments, the macroporous layer comprises pores having a size in the range of from 1 pm and 1000 pm. In accordance with the present disclosure, the size of the pores in the macroporous layer may include, in increments of 1 pm, any range between 1 pm up to and including 1000 pm. For example, the size of the pores in the macroporous substrate may be in the range of from 1 pm to 500 pm, or 5 pm to 300 pm, or 10 pm to 100 pm, etc. Typically, the size of the pores in the macroporous layer may be measured by Scanning Electron Microscopy, or Optical Microscopy, or using a Pore Size Meter for Nonwovens. The macroporous layer is typically preferred at least because the macropores not only provide less vapor transport resistance, compared to microporous or nanoporous structures, but the macroporous layer can also provide additional rigidity and mechanical strength.

[0084] The thickness of the porous substrate selected may depend on the intended application of the membrane. Generally, the thickness of the porous substrate (“T” in FIG. 1) may be greater than 10 micrometers (pm). In some embodiments, the thickness of the porous substrate may be greater than 1,000 pm, or greater than 5,000 pm. The maximum thickness depends on the intended use, but may often be less than or equal to 10,000 pm.

[0085] In certain embodiments, the porous substrate has first and second opposite major surfaces, and a thickness measured from one to the other of the opposite major surfaces in the range of from 5 pm up to and including 500 pm. In accordance with the present disclosure, the thickness of the porous substrate may include, in increments of 25 pm, any range between 5 pm and 500 pm. For example, the thickness of the porous substrate may be in the range of from 50 pm to 400 pm, or 100 pm to 300 pm, or 150 pm to 250 pm, etc.

[0086] In certain embodiments, the nanoporous layer has a thickness in the range of from 0.01 pm up to and including 10 pm. In accordance with the present disclosure, the thickness of the nanoporous layer may include, in increments of 50 nm, any range between 0.01 pm and 10 pm. For example, the thickness of the nanoporous layer may be in the range of from 50 nm to 5000 nm, or 100 nm to 3000 nm, or 500 nm to 2000 nm, etc.

[0087] In certain embodiments, the microporous layer has a thickness in the range of from 5 pm up to and including 300 pm. In accordance with the present disclosure, the thickness of the microporous layer may include, in increments of 5 pm, any range between 5 pm and 300 pm. For example, the thickness of the microporous layer may be in the range of from 5 pm to 200 pm, or 10 pm to 200 pm, or 20 pm to 100 pm, etc.

[0088] In certain embodiments, the macroporous layer has a thickness in the range of from 25 pm up to and including 500 pm. In accordance with the present disclosure, the thickness of the macroporous layer may include, in increments of 25 pm, any range between 25 pm up and 500 pm. For example, the thickness of the macroporous substrate may be in the range of from 25 pm to 300 pm, or 25 pm to 200 pm, or 50 pm to 150 pm, etc.

[0089] In certain embodiments, there may be anywhere from one to four layers in any combination within a porous substrate. The individual thickness of each layer may range from 5 nm to 1500 pm in thickness.

[0090] In certain embodiments, each layer may have a porosity that ranges from 0.5% up to and including 95%.

[0091] Gutter Layers

[0092] Composite membranes according to the present disclosure include a gutter layer comprised of a segmented polydiorganosiloxane block copolymer.

[0093] In some embodiments, the segmented polydiorganosiloxane block copolymer comprises repeating units of the following Formula I:

[0094] In Formula I:

[0095] Z is a divalent radical selected from the group consisting of phenylene, alkylene, aralkylene and cycloalkylene;

[0096] Y is selected from the group consisting of alkylene radicals of 1 to 10 carbon atoms, aralkyl radicals, and aryl radicals;

[0097] R is at least 50% methyl with the balance of the 100% of all R radicals being selected from the group consisting of a monovalent alkyl radical having from 2 to 12 carbon atoms, a substituted alkyl radical having from 2 to 12 carbon atoms, a vinyl radical, a phenyl radical, and a substituted phenyl radical;

[0098] D is selected from the group consisting of hydrogen, an alkyl radical of 1 to 10 carbon atoms, and phenyl;

[0099] B is selected from the group consisting of alkylene, aralkylene, cycloalkylene, phenylene, polyethylene oxide, polypropylene oxide, polytetramethylene oxide, polyethylene adipate, poly caprolactone, polybutadiene, and mixtures thereof, and a radical completing a ring structure including A to form a heterocycle;

[0100] A is selected from the group consisting of -O- and -N(G)- where G is selected from the group consisting of hydrogen, an alkyl radical of 1 to 10 carbon atoms, phenyl, and a radical which completes a ring structure including B to form a heterocycle; n is a number which is 10 or larger; and m is a number which is 0 to 25. In a preferred block copolymer of Formula I, Z is selected from the group consisting of hexamethylene, methylene bis-(phenylene), isophorone, tetramethylene, cyclohexylene, and methylene dicyclohexylene and R is methyl.

[0101] Further details regarding a block copolymer of Formula I and methods of making the block copolymer of Formula I are described in U.S. Patent No. 5,512,650 (Leir et al.), the entire disclosure of which is incorporated herein by reference in its entirety.

[0102] In some embodiments, the segmented polydiorganosiloxane copolymer comprises the repeating unit of Formula II:

[0103] In Formula II, each R is a moiety that, independently, is an alkyl moiety, preferably having about 1 to 12 carbon atoms, and may be substituted with, for example, trifluoroalkyl or vinyl groups, a vinyl radical or higher alkenyl radical preferably represented by the formula R2(CH2)aCH=CH2wherein R2is — (CH2)4— or — CH2)CCH=CH — and a is 1, 2 or 3; b is 0, 3 or 6; and c is 3, 4 or 5, a cycloalkyl moiety having from about 6 to 12 carbon atoms and may be substituted with alkyl, fluoroalkyl, and vinyl groups, or an aryl moiety preferably having from about 6 to 20 carbon atoms and may be substituted with, for example, alkyl, cycloalkyl, fluoroalkyl arid vinyl groups or R is a perfluoroalkyl group as described in U.S. Pat. No. 5,028,679, and incorporated herein, or a fluorine-containing group, as described in U.S. Pat. No. 5,236,997 and incorporated herein, or a perfluoroether-containing group, as described in U.S. Pat. Nos. 4,900,474 and 5,118,775 and incorporated herein; preferably at least 50% of the R moieties are methyl radicals with the balance being monovalent alkyl or substituted alkyl radicals having from 1 to 12 carbon atoms, alkenylene radicals, phenyl radicals, or substituted phenyl radicals; each Z is a polyvalent radical that is an arylene radical or an aralkylene radical preferably having from about 6 to 20 carbon atoms, an alkylene or cycloalkylene radical preferably having from about 6 to 20 carbon atoms, preferably Z is 2,6-tolylene, 4,4'-methylenediphenylene, 3,3'-dimethoxy-4,4'- biphenylene, tetramethyl-m-xylylene, 4,4'-methylenedicyclohexylene, 3,5,5-trimethyl-3- methylenecyclohexylcne, 1,6-hexamethylene, 1,4-cyclohexylene, 2,2,4-trimethylhexylene and mixtures thereof; each Y is a polyvalent radical that independently is an alkylene radical of 1 to 10 carbon atoms, an aralkylene radical or an arylene radical preferably having 6 to 20 carbon atoms; each D is selected from the group consisting of hydrogen, an alkyl radical of 1 to 10 carbon atoms, phenyl, and a radical that completes a ring structure including B or Y to form a heterocycle; where B is a polyvalent radical selected from the group consisting of alkylene, aralkylene, cycloalkylene, phenylene, polyalkylene oxide, including for example, polyethylene oxide, polypropylene oxide, polytetramethylene oxide, and copolymers and mixtures thereof; m is a number that is 0 to 1000; n is a number that is at least 1, preferably 10 to 2000; and p is a number that is at least 10, preferably 15 to 2000, more preferably 30 to 1500.

[0104] In some presently preferred embodiments, at least 50 percent, at least 60 percent, at least 70 percent, at least 80 percent, at least 90 percent, or even 100% of the R groups are methyl.

[0105] Useful silicone polyurea block copolymers are disclosed in, e.g., U.S. Pat. Nos. 5,512,650, 5,214,119, and 5,461,134, 7,078,093 (Sheridan et al.), WO 96 / 35458, WO 98 / 17726, WO 96 / 34028, WO 96 / 34030 and WO 97 / 40103, and incorporated herein by reference in their entireties.

[0106] In some embodiments, the segmented polydiorganosiloxane copolymer comprises the repeating unit of Formula III:

[0107] III.

[0108] In Formula III, each R1is independently an alkyl, haloalky 1, aralkyl, alkenyl, aryl, or aryl substituted with an alkyl, alkoxy, or halo; each R2is independently an H, alkyl, haloalkyl, aralkyl, alkenyl, aryl, or aryl substituted with an alkyl, alkoxy, or halo, or two R2groups taken together form a ring; each D is independently hydrogen or alkyl or D taken together with G and with the nitrogen to which they are both attached forms a heterocyclic group; each Y is independently an alkylene, aralkylene, or a combination thereof;

[0109] L is an alkylene, alkenylene, alkynylene, arylene, heteroarylene, heterocyclene, aralkylene, or a bond; each G is an alkylene, heteroalkylene, polydiorganosiloxane, arylene, aralkylene, or a combination thereof; subscript n is a number that is 1 to 1500; subscript p is a number that is at least 1; and subscript q is a number that is 0 to 1000.

[0110] Group G in Formula III is a residual unit that is equal to a diamine compound of formula DHN- G-NHD minus the two amino groups (i.e., — NHD groups). The diamine can have primary or secondary amino groups. Group D is hydrogen or alkyl (e.g., an alkyl having 1 to 10, 1 to 6, or 1 to 4 carbon atoms) or D taken together with G and with the nitrogen to which they are both attached forms a heterocyclic group (e.g., DHN-G-NHD is piperazine). In most embodiments, D is hydrogen or an alkyl. In many embodiments, both of the amino groups of the diamine are primary amino groups (i.e., both D groups are hydrogen) and the diamine is of formula H2N-G-NH2.

[0111] In some embodiments, G is an alkylene, heteroalkylene, polydiorganosiloxane, arylene, aralkylene, or a combination thereof. Suitable alkylenes often have 2 to 10, 2 to 6, or 2 to 4 carbon atoms. Exemplary alkylene groups include ethylene, propylene, butylene, and the like. Suitable heteroalkylenes are often polyoxyalkylenes such as polyoxyethylene having at least 2 ethylene units, polyoxypropylene having at least 2 propylene units, or copolymers thereof. Exemplary polydiorganosiloxanes include, but are not limited to, polydimethylsiloxanes with alkylene Y groups. Suitable aralkylene groups usually contain an arylene group having 6 to 12 carbon atoms bonded to an alkylene group having 1 to 10 carbon atoms. Some exemplary aralkylene groups are phenylene-alkylene where the phenylene is bonded to an alkylene having 1 to 10 carbon atoms, 1 to 8 carbon atoms, 1 to 6 carbon atoms, or 1 to 4 carbon atoms. As used herein with reference to group G, “a combination thereof’ refers to a combination of two or more groups selected from an alkylene, heteroalkylene, polydiorganosiloxane, arylene, and aralkylene. A combination can be, for example, an aralkylene bonded to an alkylene (e.g., alkylene-arylene-alkylene). In one exemplary alkylene-arylene-alkylene combination, the arylene is phenylene and each alkylene has 1 to 10, 1 to 6, or 1 to 4 carbon atoms.

[0112] Bisoxazolone compounds, including those shown below, can be prepared by known methods, as in Cleaver, C. S.; Pratt, B. C. J. Am. Chem. Soc. 1955, 7, 1544-1546.

[0113] Polymers of the present disclosure in which q is 0 are prepared as described in the Examples below for the case of Monomer 2 reacting with a 20k PDMS diamine in ethyl acetate at 70°C. Inclusion of a diamine of formula DHN-G-NHD produces a polymer in which q is 1 or greater.

[0114] When the segmented polydiorganosiloxane copolymer is of any of Formula I, Formula II, or Formula III, preferably, n and m (of Formula I), n, m, and p (of Formula II), or n, p, and q (of Formula III) are selected so that the polydiorganosiloxane (e.g., block or segment) comprises at least 90 weight percent (wt.%), 91 wt.%, 92 wt.%, 93 wt.%, 94 wt.%, 95 wt.%, 96 wt.%, or even at least 97 wt.% of the polydiorganosiloxane copolymer; and 99.9 wt.% or less, 99.8 wt.%, 99.7 wt.%, 99.5 wt.%, 99 wt.%, 98.5 wt.%, or even 98 wt.% or less of the polydiorganosiloxane copolymer. In some presently preferred embodiments, the gutter layer is comprised of a segmented polydiorganosiloxane copolymer, regardless of its specific formula, having greater than 90% polydiorganosiloxane (e.g., blocks or segments).

[0115] The polydiorganosiloxane block copolymer is a linear, block copolymer and can be an elastomeric material. Polydiorganosiloxane block copolymers can be formulated to include greater than 50 weight percent polydiorganosiloxane segments based on the weight of the copolymer. The weight percent of the diorganosiloxane in the polydiorganosiloxane block copolymers can be increased by using higher molecular weight polydiorganosiloxane segments to provide greater than 60 weight percent, greater than 70 weight percent, greater than 80 weight percent, greater than 90 weight percent, greater than 95 weight percent, or greater than 98 weight percent of the polydiorganosiloxane segments in the polydiorganosiloxane block copolymers. Higher amounts of the polydiorganosiloxane can be used to prepare elastomeric materials with lower modulus while maintaining reasonable strength.

[0116] In some embodiments, polydiorganosiloxane copolymers are phase separated to form hard domains after solvent evaporation. In some embodiments, hard domains from phase separated polydiorganosiloxane copolymers are able to form strong interactions with the separation layer material, for example by hydrogen bonding.

[0117] In some embodiments, a gutter layer according to the present disclosure exhibits an X-ray scattering peak centered between 0.03-0.6 A'1that corresponds to a d spacing of 1 to 20 nm when analyzed by the Small Angle X-ray Scattering Method.

[0118] The polydiorganosiloxane copolymers are soluble in many common organic solvents such as, for example, toluene, tetrahydrofuran, dichloromethane, aliphatic hydrocarbons (e.g., alkanes such as hexane), or mixtures thereof.

[0119] The polydiorganosiloxane block copolymers can be cast from solvents as film, molded or embossed in various shapes, or extruded into films. The high temperature stability of the copolymeric material makes them well suited for extrusion methods of film formation.

[0120] Optionally, the gutter layer is corona treated or plasma treated to increase the surface energy and enhance the wet out and adhesion of the separation layer. In such cases, the treated surface (i.e., first major surface) of the gutter layer exhibits an advancing water contact angle of less than 100°. Advancing water contact angle may be determined using a surface analyzer, such as the “Handheld Surface Analyst” commercially available from Brighton Science (Cincinnati, Ohio).

[0121] Separation Layers

[0122] Composite membranes according to the present disclosure include at least one separation layer. As noted above, the term “separation layer' ’ refers to a layer that functions to selectively separate at least two gases from each other, for example carbon dioxide from other gases in a mixture.

[0123] Optionally, the separation layer is comprised of a poly(ether-block-amide) (PEBA) copolymer. PEBA copolymers have been used for carbon dioxide separation, for instance as described in detail in “Poly (amide-6-b-ethylene oxide) multilayer composite membrane for carbon dioxide separation”, Ren et al., International Journal of Greenhouse Gas Control, 2012, volume 8, pp. 111-120.

[0124] Some suitable commercially available PEBA copolymers included for instance and without limitation, those available under the trade designation “PEB AX” from Arkema Inc. (King of Prussia, PA) (e.g., PEBAX grades 1657, 2533, 1074, 3533, 4033, 5533, 4011, or Rnew 30R51). Such PEBAX materials are thermoplastic block copolymers containing both rigid polyamide blocks and soft polyether blocks. In some presently preferred embodiments, the separation layer comprises a poly(ether-block- amide) copolymer in which the ether is polyethylene oxide or poly(tetramethylene oxide) and the amide is a saturated aliphatic polyamide segment (e.g., nylon 6 or nylon 12).

[0125] When there are two separation layers, the layers may be the same or different. In some cases, the second separation layer comprises a poly(ether-block-amide) copolymer.

[0126] The one or more separation layers may be formed by applying a coating of a solution containing a PEBA copolymer on a layer of the composite membrane (e.g., the gutter layer, another (optional) separation layer, or an (optional) interfacial layer), and allowing the coating to dry. In some cases, it may be preferred to employ a solvent component, which swells the gutter layer material when coating the separation layer to minimize dewetting and / or for forming strong material interactions between the two layers.

[0127] Interfacial Layers

[0128] Composite membranes according to the present disclosure optionally include an interfacial layer. As noted above, the term “interfacial layer” refers to a layer that forms a common boundary between two other layers. It is sometimes challenging to achieve good adhesion between a gutter layer and a directly adjacent layer, such as a separation layer. One approach to minimizing separation between the gutter layer and the adjacent layer is to incorporate an interfacial layer between the two.

[0129] In certain embodiments, an optional interfacial layer is comprised of a surfactant, such as one or more nonionic, anionic, cationic, or amphoteric surfactants. Suitable surfactants include for instance and without limitation, C8-C18 alkane sulfonates; C8-C18 secondary alkane sulfonates; alkylbenzene sulfonates; C8-C18 alkyl sulfates; alkylether sulfates; sodium laureth 4 sulfate; sodium laureth 8 sulfate; dioctylsulfosuccinate, sodium salt; lauroyl lacylate; stearoyl lactylate; silicone poly(ether) copolymers; amine functional organosilicone; siloxane compounds; or any combination thereof. One or more surfactants can be applied by conventional methods, such as by coating a solution containing the surfactant on the surface of a (e.g., gutter) layer and allowing the coating to dry.

[0130] Protection Layers

[0131] Composite membranes according to the present disclosure optionally include a protection layer. As noted above, the term “protection layer” refers to a layer that functions to shield at least one other layer from damage. Any highly gas permeable materials can be used for a protection layer; such as a crosslinked poly dimethylsiloxane (PDMS), poly(l -trimethylsilyl- 1 -propyne) (PTMSP), or a plasma generated coating or a glassy perfluoropolymer (e.g., both as described in detail in WO 2017 / 004495 (Zhou et al.)). In certain presently preferred embodiments, a protection layer is comprised of or consists of the same material as the gutter layer (i.e., a segmented polydiorganosiloxane block copolymer comprising at least two repeat units of Formula I), which is described in detail above. Such a protection layer may be applied to another layer of the composite membrane (e.g., a separation layer) in the same manner as the gutter layer may be applied. In some embodiments, an optional protection layer is disposed on the (e.g., first) separation layer opposite the gutter layer. Often, a protection layer is an exterior layer of the composite membrane.

[0132] Typically, the (optional) protection layer has an average thickness of 10 nanometers (nm) or more, such as 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm 200 nm, 210 nm,

[0133] 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm, or 300 nm or more; and 400 nm or less, 390 nm, 380 nm, 370 nm, 360 nm, 350 nm, 340 nm, 330 nm, 320 nm, 310 nm, 300 nm, 280 nm, 260 nm, 240 nm, 220 nm, 200 nm, 180 nm, 160 nm, 140 nm, 120 nm, 100 nm, 75 nm, or 50 nm or less.

[0134] Stated another way, in certain cases the optional protection layer has an average thickness of 10 nm to 400 nm.

[0135] Methods

[0136] In a second aspect, a method of separating gases is provided. The method comprises: passing a mixture of gases through a composite membrane according to any embodiment of the first aspect described in detail above, wherein the passing operation comprises passing the mixture of gases through the separation layer prior to the gutter layer. Stated another way, referring back to FIG. 1, the mixture of gases in contacted with the composite membrane 100 in a direction such that the mixture of gases first passes through the separation layer 130 towards the gutter layer 120 and then the porous substrate 110. Similarly, referring back to FIG. 2, the mixture of gases is contacted with the composite membrane 200 in a direction such that the mixture of gases first passes through the optional protection layer 150 towards the separation layer 130, optional second separation layer 132, optional interfacial layer 140, the gutter layer 120, and then the porous substrate 110. Preferably, the mixture of gases includes carbon dioxide.

[0137] Exemplary Embodiments

[0138] In a first embodiment, the present disclosure provides a composite membrane comprising a porous substrate, a gutter layer comprising a segmented polydiorganosiloxane copolymer, and a separation layer, wherein the gutter layer is disposed between the porous substrate and the separation layer.

[0139] In a second embodiment, the present disclosure provides a composite membrane according to the first embodiment, wherein the segmented polydiorganosiloxane copolymer comprises the repeating unit of Formula I:

[0140] I, wherein:

[0141] Z is a divalent radical selected from the group consisting of phenylene, alkylene, aralkylene and cycloalkylene; Y is selected from the group consisting of alkylene radicals of 1 to 10 carbon atoms, aralkyl radicals, and aryl radicals; R is at least 50% methyl with the balance of the 100% of all R radicals being selected from the group consisting of a monovalent alkyl radical having from 2 to 12 carbon atoms, a substituted alkyl radical having from 2 to 12 carbon atoms, a vinyl radical, a phenyl radical, and a substituted phenyl radical; D is selected from the group consisting of hydrogen, an alkyl radical of 1 to 10 carbon atoms, and phenyl; B is selected from the group consisting of alkylene, aralkylene, cycloalkylene, phenylene, polyethylene oxide, polypropylene oxide, polytetramethylene oxide, polyethylene adipate, polycaprolactone, polybutadiene, and mixtures thereof, and a radical completing a ring structure including A to form a heterocycle; A is selected from the group consisting of -O- and -N(G)- where G is selected from the group consisting of hydrogen, an alkyl radical of 1 to 10 carbon atoms, phenyl, and a radical which completes a ring structure including B to form a heterocycle; n is a number which is 10 or larger; and m is a number which is 0 to 25.

[0142] In a third embodiment, the present disclosure provides a composite membrane according to the first embodiment, wherein the segmented polydiorganosiloxane copolymer comprises the repeating unit of Formula II: wherein: each R is a moiety that, independently, is an alkyl moiety, a substituted alkyl moiety, a cycloalkyl moiety, a substituted cycloalkyl moiety, an aryl moiety, or a substituted aryl moiety; each Z is a polyvalent radical that is an arylene radical or an aralkylene radical, an alkylene or cycloalkylene radical; each Y is a polyvalent radical that independently is an alkylene radical of 1 to 10 carbon atoms, an aralkylene radical or an arylene radical; each D is selected from the group consisting of hydrogen, an alkyl radical of 1 to 10 carbon atoms, phenyl, and a radical that completes a ring structure including B or Y to form a heterocycle; where B is a polyvalent radical selected from the group consisting of alkylene, aralkylene, cycloalkylene, phenylene, polyalkylene oxide, and copolymers and mixtures thereof; m is a number that is 0 to 1000; n is a number that is at least 1; and p is a number that is at least 10.

[0143] In a fourth embodiment, the present disclosure provides a composite membrane according to the third embodiment, wherein in Formula II at least 50 percent of the R moieties are methyl.

[0144] In a fifth embodiment, the present disclosure provides a composite membrane according to the third embodiment or the fourth embodiment, wherein in Formula II p is 30 to 1500.

[0145] In a sixth embodiment, the present disclosure provides a composite membrane according to any of the third through fifth embodiments, wherein in Formula II n is 10 to 2000.

[0146] In a seventh embodiment, the present disclosure provides a composite membrane according to any of the third through sixth embodiments, wherein in Formula II Z is 2,6-tolylene, 4,4'- methylenediphenylene, 3,3'-dimethoxy-4,4'-biphenylene, tetramethyl-m-xylylene, 4,4'- methylenedicyclohexylene, 3,5,5-trimethyl-3-methylenecyclohexylcne, 1,6-hexamethylene, 1,4- cyclohexylene, 2,2,4-trimethylhexylene, or mixtures thereof. In an eighth embodiment, the present disclosure provides a composite membrane according to the first embodiment, wherein the segmented polydiorganosiloxane copolymer comprises the repeating unit of Formula III:

[0147] III, wherein: each R1is independently an alkyl, haloalkyl, aralkyl, alkenyl, aryl, or aryl substituted with an alkyl, alkoxy, or halo; each R2is independently an H, alkyl, haloalkyl, aralkyl, alkenyl, aryl, or aryl substituted with an alkyl, alkoxy, or halo, or two R2groups taken together form a ring; each D is independently hydrogen or alkyl or D taken together with G and with the nitrogen to which they are both attached forms a heterocyclic group; each Y is independently an alkylene, aralkylene, or a combination thereof; L is an alkylene, alkenylene, alkynylene, arylene, heteroarylene, heterocyclene, aralkylene, or a bond; each G is an alkylene, heteroalkylene, polydiorganosiloxane, arylene, aralkylene, or a combination thereof; subscript n is a number that is 1 to 1500; subscript p is an number that is at least 1; and subscript q is a number that is 0 to 1000.

[0148] In a ninth embodiment, the present disclosure provides a composite membrane according to any of the first through eighth embodiments, wherein the segmented polydiorganosiloxane block copolymer has greater than 90% polydiorganosiloxane blocks.

[0149] In a tenth embodiment, the present disclosure provides a composite membrane according to any of the first through ninth embodiments, wherein the separation layer is selective for carbon dioxide.

[0150] In an eleventh embodiment, the present disclosure provides a composite membrane according to any of the first through tenth embodiments, wherein the separation layer comprises a polyether (co)polymer.

[0151] In a twelfth embodiment, the present disclosure provides a composite membrane according to any of the first through eleventh embodiments, wherein the separation layer comprises a poly(ether-block- amide) copolymer.

[0152] In a thirteenth embodiment, the present disclosure provides a composite membrane according to any of the first through twelfth embodiments, wherein the separation layer comprises a poly(ether-block- amide) copolymer in which the ether is polyethylene oxide or poly(tetramethylene oxide) and the amide is a saturated aliphatic polyamide segment.

[0153] In a fourteenth embodiment, the present disclosure provides a composite membrane according to any of the first through thirteenth embodiments, wherein the separation layer is a first separation layer and the composite membrane further comprises a second separation layer disposed between the gutter layer and the first separation layer.

[0154] In a fifteenth embodiment, the present disclosure provides a composite membrane according to the fourteenth embodiment, wherein the second separation layer comprises a poly(ether-block-amide) copolymer. In a sixteenth embodiment, the present disclosure provides a composite membrane according to any of the first through fifteenth embodiments, further comprising a protection layer disposed on the first separation layer opposite the gutter layer.

[0155] In a seventeenth embodiment, the present disclosure provides a composite membrane according to the sixteenth embodiment, wherein the protection layer has an average thickness of 10 nanometers (nm) to 400 nm.

[0156] In an eighteenth embodiment, the present disclosure provides a composite membrane according to the sixteenth embodiment or the seventeenth embodiment, wherein the protection layer comprises a segmented polydiorganosiloxane block copolymer having greater than 90% poly diorgano siloxane blocks.

[0157] In a nineteenth embodiment, the present disclosure provides a composite membrane according to any of the sixteenth through eighteenth embodiments, wherein the protection layer comprises a crosslinked poly dimethylsiloxane.

[0158] In a twentieth embodiment, the present disclosure provides a composite membrane according to any of the first through nineteenth embodiments, wherein the segmented polydiorganosiloxane block copolymer is a segmented polydiorganosiloxane polyurea block copolymer.

[0159] In a twenty -first embodiment, the present disclosure provides a composite membrane according to any of the first through twentieth embodiments, wherein the porous substrate has a first major surface having a) an average pore size of less than 100 nm and b) a porosity of 0.1 to 20 percent.

[0160] In a twenty-second embodiment, the present disclosure provides a composite membrane according to any of the first through twenty -first embodiments, wherein the porous substrate comprises a polymeric material selected from the group consisting of polyacrylonitrile (PAN), polydimethylsiloxane copolymer, polysulfone, cellulose acetate, polyether sulfone (PES), polyvinylidene fluoride (PVDF), polyetherimide (PEI), polyaminosiloxane, polydimethylphenylene oxide (PPO), polyvinylpyridine (PVP), ethylene chlorotrifluoroethylene (ECTFE), polytetrafluoroethylene (PTFE), polyamide, polyethylene, polypropylene, polymethylpentene, cellulose nitrate, polyester, polycarbonate, and polyimide.

[0161] In a twenty -third embodiment, the present disclosure provides a composite membrane according to any of the first through twenty-second embodiments, wherein the gutter layer exhibits an advancing water contact angle of less than 100°.

[0162] In a twenty -fourth embodiment, the present disclosure provides a composite membrane according to any of the first through twenty -third embodiments, exhibiting a carbon dioxide gas to nitrogen gas selectivity of at least 20 CO2 / N2.

[0163] In a twenty -fifth embodiment, the present disclosure provides a composite membrane according to any of the first through twenty -fourth embodiments, exhibiting a carbon dioxide gas permeance of at least 100 gas permeation units (GPU).

[0164] In a twenty-six embodiment, the present disclosure provides a composite membrane according to any of the first through twenty -fifth embodiments, wherein the gutter layer exhibits an X-ray scattering peak centered between 0.03-0.6 A'1that corresponds to a d spacing of 1 to 20 nm when analyzed by the Small Angle X-ray Scattering Method. In a twenty-seventh embodiment, the present disclosure provides a composite membrane according to any of the first through twenty -sixth embodiments, further comprising surface modification of the gutter layer that enhances adhesion with separation layer.

[0165] In a twenty-eighth embodiment, the present disclosure provides a method of separating gases. The method comprises passing a mixture of gases through a composite membrane according to any of the first through twenty-seventh embodiments, wherein the passing operation comprises passing the mixture of gases through the separation layer prior to the gutter layer.

[0166] In a twenty -ninth embodiment, the present disclosure provides a method of separating gases according to the twenty-eighth embodiment, wherein the mixture of gases comprises carbon dioxide.

[0167] EXAMPLES

[0168] The following Examples are merely for illustrative purposes and are not meant to be overly limiting on the scope of the appended claims.

[0169] Unless otherwise noted or otherwise apparent from the context, all parts, percentages, ratios, and the like in the Examples and the rest of the specification are provided on the basis of weight.

[0170] Materials Used in the Examples

[0171] • Silicone poly(urea) (SPU1 and SPU2) as prepared in Example 19 and Example 18 in patent US7078093, separately, without the added MQ tackifier.

[0172] • Toluene, EMD Millipore, Burlington MA

[0173] • Isopropanol, VWR International LLC. Radnor, PA

[0174] • Ethanol, EMD Millipore, Burlington, MA

[0175] • Water, distilled water filtered with Millipore filtration system

[0176] • PEBAX 1657, PEBAX MH1657, Arkema Inc. King of Prussia, PA

[0177] • PEBAX RNEW 30R51 SA01, Arkema Inc. King of Prussia, PA

[0178] • PEBAX 1074, Arkema Inc. King of Prussia, PA

[0179] • PAN350, polyacrylonitrile substrate, Nanostone Water, formerly known as Sepro Membranes Inc., Oceanside, CA, used as received

[0180] • Ethyl Acetate, Honeywell Charlotte, NC PDMS Diamine 20,000 molecular weight, a polydimethylsiloxane diamine of the following formula: , with a number average molecular weight of approximately 20,000 g / mole prepared according to U.S. Patent No. 5,214,119 (Leir et al.)

[0181] • Dytek A, 2-methylpentane-l,5-diamine, Invista Wichita, KS

[0182] • Molecular Sieves, UOP Corporation Tonawanda, NY

[0183] Membrane permeation testing

[0184] Membrane permeation of pure gases (CO2 and N2) was tested using a constant pressure-variable volume approach with membrane disc samples of 47 mm diameter (effective diameter 42 mm). The test system includes a membrane cell (XX4404700, Millipore Sigma) installed between one feed gas reservoir (upstream) and downstream connected to mass flow meter (FMA-4107, Omega Engineering). Both upstream and downstream were flushed with a testing gas for 10 seconds after mounting a membrane sample. One pure gas (CO2or N2) of 10-50 psi was introduced to the upstream reservoir. The gas permeated the membrane sample for 90 seconds to reach a stable flowrate at the downstream before gas permeance measurement is taken for another 60 seconds. The gas permeance (GPU; 1 GPU = 10'6cm3(STP) cm'2s'1cmHg'1) was calculated as follows where, ■ (cm3(STP) s'1), p (cmHg), and A (cm2) indicate flowrate at standard-temperature-pressure at downstream, upstream pressure, and membrane area, respectively. CO2 / N2 gas selectivity was calculated from the permeance of pure gases

[0185] Small Angle X-ray Scattering Method

[0186] SAXS (small angle X-ray scattering)

[0187] A small piece (~ 1 cm x 1 cm) of each film sample was taped to Solid sample holder directly. Transmission geometry data were collected under vacuum (< 0.1 mbar) by use of a Xeuss 3.0 SAXS lab Beamline, a pfocus Cu Ka( / . = 1.54 A) radiation, and a Eiger2 R hybrid pixel photon counting 2D detector (IM). The diffractometer is fitted with two scatterless slits modules for beam collimation, a sample stage assembly with motorized X-Z translations perpendicular to beam direction for sample positioning, and a diffracted beam path chamber with rails for motion of the detector stage with variable sample-detector (SD) distance up to 1750 millimeters (mm). SAXS data were collected in selected predefined configurations (e.g., slit opening and SD distance) with a beam size of 0.4-0.8 mm on sample and typical exposure time of minutes-hours to obtain optimized resolution and counting statistics. X-ray generator settings of 50 kV and 0.6 mA were employed. Scattering profiles of open beam were collected at identical conditions as corresponding samples to subtract background data. Data reduction and analysis were conducted using Xenocs XSACT software.

[0188] Inherent Viscosity (IV)

[0189] Inherent viscosity measurements were performed at 27 °C on a LAUDA PVS 1 viscosity system obtained from Lauda-Brinkman (Delran, NJ) utilizing size 50 capillary viscometers (Part #9721-A00). All polymer samples were analyzed as an ethyl acetate solution at a concentration of 0.2 g / dL and IV measurements are reported in dL / g.

[0190] Coat solution preparation

[0191] PEBAX solutions

[0192] Polymer resins (PEBAX 1657, PEBAX 1074, PEBAX RNEW) as received were mixed with solvent mixtures in tightly sealed jars with a stirring bar. Jars were immersed in a heated water bath while stirring. Water bath temperature was set at 90-95°C. Dissolution process took up to 5 horns. Solutions were cooled to room temperature before using them for coating.

[0193] Example 1 for adhesion testing

[0194] A 2 wt.% solids SPU2 solution was formulated using a solvent mixture containing 80% Toluene and 20% isopropanol. The SPU2 solution was poured into a PTFE plate to form a film by solvent evaporation under ambient temperature for at least 2 hours; a solid film was formed in the plate.

[0195] A 5 wt.% solids PEBAX 1657 solution was formulated using a solvent mixture containing 30% Toluene, 55% isopropanol and 15% water. The solution was coated on top of the PTFE plate supported by the film above. A second layer of film was formed when drying up.

[0196] A SCOTCH tape (3M Company, St. Paul, MN) was pressed to the PEBAX layer to peel films from the PTFE plate.

[0197] When the SCOTCH tape peeled PEBAX, both layers were removed from the PTFE plate as shown in FIG. 3. In particular, FIG. 3 is a schematic cross-sectional view of results of the peel experiment for Example 1 multilayer structure 300. It can be seen that the PEBAX layer 310 and the SPU layer 320 remained attached to each other while the SPU layer 320 was separated from the PTFE plate 330. The PEBAX layer 310 and the SPU layer 320 could not be separated at all without breaking the laminated film. It implies a strong adhesion between SPU and PEBAX. Examples 2-9 SPU coatability onto a porous substrate

[0198] Two grades of silicone poly(urea) (SPU1 and SPU2) were dissolved in solvent mixtures with various Toluene wt.% in a solvent mixture with isopropanol to formulate a 2.0 wt.% solution. PAN350 used as received was coated with silicone polyurea solutions using a Mayer rod (RD Specialties, Inc., Webster, NY). Target dry thickness of SPU was 0.2 micrometers (um).

[0199] Table 1. SPU coated membranes and their gas performance

[0200] Examples 10-17, Composite membranes with or without SPU gutter layer

[0201] In Examples 10-17, composite membranes were prepared from either SPU2 and / or separation materials (PEBAX) on a porous substrate PAN350. Both membranes in Examples 10 and 11 do not have SPU layer before applying PEBAX materials. Very low selectivity was observed by directly applying separation materials onto porous substrates. In contrast, composite membranes in Examples 12 and 13 were coated with SPU2 first before applying separation layer material. They gave significantly higher gas selectivity than the membranes in Example 10 and 11 without SPU2 as a gutter layer. Furthermore, the presence of gutter layer increased gas permeance by 2x.

[0202] Composite membranes of Examples 14-17 included the highly selective material PEBAX 1657. Surprisingly, no dewetting issue was found by applying PEBAX1657 coating solution to SPU coated membrane. After drying, PEBAX strongly adheres to SPU layer; peel testing similar to Example 1 shows no separation between PEBAX layer and SPU layer. Gas selectivity was dramatically improved with those membranes. In addition, the presence of additional SPU layer as protection and / or the solvent composition for PEBAX appear impact membrane performance as well. Table 2. Solutions for coating separation materials Table 3. SPU based composite membranes and their gas performance

[0203] PEBAX density: PEBAX 1074 1.07g / cc; PEBAX RNEW l.Olg / cc; PEBAX 1657 1.14g / cc

[0204] Two grades of silicone poly(urea) (SPU1-85C and SPU2-85D) films were analyzed using SAXS. Both samples showed the presence of uniformly spaced phase separated domains from a characteristic scattering peak. This uniformly distributed hard segments within gutter layer, which have potential interactions such as hydrogen bonding with separation layer and porous substrate probably mitigate the dewetting issue of gutter layer and its intrusion into the porous substate. The domain spacing of SPU 1 estimated from the center peak position is smaller than SPU2; however, the peak from SPU2 is broader with a higher intensity, which implies the existence of broader size of distribution of domains and a larger population of domains, which may prevent material intrusion more effectively while coating onto a porous substrate. Example 18

[0205] A jacketed 3-gallon stainless steel reaction vessel with a mechanical stirrer was charged with the silicone diamine (AEW = 10,115 g / mol, 1351 g, 133.6 meq) and ethyl acetate (3152 g) that had been dried over 4A molecular sieves. The contents were brought to 70 °C, and 19.760 g (131.6 meq) of Monomer 2 was added. The vessel was sealed under nitrogen and allowed to react at 70 °C for 66 hours. The viscous solution was transferred to a plastic tray, and the solvent was removed via evaporation to afford a clear, colorless elastomer having an inherent viscosity in ethyl acetate of 1.04 dL / g.

[0206] 20k PDMS Diamine

[0207] Table 4.

[0208] Examples 19-30

[0209] Table 5. Chemical compositions of additional SPUs Note: SPU synthesis follows the process disclosed in patent US7078093 without the added MQ tackifier

[0210] 12 new silicone poly(urea) (SPU), shown in Table 5, were diluted with solvent mixtures to formulate 2.0 wt.% solutions. PAN350 was used as received was coated with silicone polyurea solutions using a Mayer rod (RD Specialties, Inc., Webster, NY). Target dry thickness of each SPU was 0.2 micrometers (um). As can be seen in Table 6, most of SPU coated membranes reach CO2 / N2 selectivities close to the inherent value (10.8) of silicone rubber (Richard W. Baker, Membrane Technology and Applications, 2ndedition, John Wiley & Sons, Ltd, 2004). SPU coated membranes showed up to 14623 GPU gas permeance, offering the minimum gas transport resistance with a gutter layer, while retaining a good selectivity.

[0211] The new SPUs were analyzed using SAXS using dry fdms. All materials showed characteristic scattering peaks indicating the presence of spaced phase separated domains, as can be seen in FIG. 5. Phase separation domains help retain materials on top of a porous substrate to form a solid film as a gutter layer.

[0212] Table 6. SPU coated membranes and their gas performance

[0213] Examples 31-34, Composite membranes with SPU gutter layer

[0214] In Examples 31-34, composite membranes were prepared from new SPUs, separately, followed by a separation material (PEBAX 1657) on a porous substrate PAN350. PEBAX was applied using 2 wt. % solution in a same solvent composition as in Example 14. No third layer was applied for these composite membranes for protection. As can be seen in Table 7, a highly CO2 selective composite membrane can be achieved, for example, from SPU 13 and SPU 14. Table 7. SPU based composite membranes and their gas performance

[0215] Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and / or equivalent implementations can be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof. Furthermore, all publications and patents referenced herein are incorporated by reference in their entirety to the same extent as if each individual publication or patent was specifically and individually indicated to be incorporated by reference. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in the preceding description prevails.

Claims

What is claimed is:

1. A composite membrane comprising: a porous substrate; a gutter layer comprising a segmented poly diorgano siloxane copolymer; and a separation layer, wherein the gutter layer is disposed between the porous substrate and the separation layer.

2. The composite membrane of claim 1, wherein the segmented polydiorganosiloxane copolymer comprises the repeating unit of Formula I:I. wherein:Z is a divalent radical selected from the group consisting of phenylene, alkylene, aralkylene and cycloalkylene;Y is selected from the group consisting of alkylene radicals of 1 to 10 carbon atoms, aralkyl radicals, and aryl radicals;R is at least 50% methyl with the balance of the 100% of all R radicals being selected from the group consisting of a monovalent alkyl radical having from 2 to 12 carbon atoms, a substituted alkyl radical having from 2 to 12 carbon atoms, a vinyl radical, a phenyl radical, and a substituted phenyl radical;D is selected from the group consisting of hydrogen, an alkyl radical of 1 to 10 carbon atoms, and phenyl;B is selected from the group consisting of alkylene, aralkylene, cycloalkylene, phenylene, polyethylene oxide, polypropylene oxide, polytetramethylene oxide, polyethylene adipate, polycaprolactone, polybutadiene, and mixtures thereof, and a radical completing a ring structure including A to form a heterocycle;A is selected from the group consisting of -O- and -N(G)- where G is selected from the group consisting of hydrogen, an alkyl radical of 1 to 10 carbon atoms, phenyl, and a radical which completes a ring structure including B to form a heterocycle; n is a number which is 10 or larger; and m is a number which is 0 to 25.

3. The composite membrane of claim 1, wherein the segmented polydiorganosiloxane copolymer comprises the repeating unit of Formula II:II, wherein: each R is a moiety that, independently, is an alkyl moiety, a substituted alkyl moiety, a cycloalkyl moiety, a substituted cycloalkyl moiety, an aryl moiety, or a substituted aryl moiety; each Z is a polyvalent radical that is an arylene radical or an aralkylene radical, an alkylene or cycloalkylene radical; each Y is a polyvalent radical that independently is an alkylene radical of 1 to 10 carbon atoms, an aralkylene radical or an arylene radical; each D is selected from the group consisting of hydrogen, an alkyl radical of 1 to 10 carbon atoms, phenyl, and a radical that completes a ring structure including B or Y to form a heterocycle; where B is a polyvalent radical selected from the group consisting of alkylene, aralkylene, cycloalkylene, phenylene, polyalkylene oxide, and copolymers and mixtures thereof; m is a number that is 0 to 1000; n is a number that is at least 1; and p is a number that is at least 10.

4. The composite membrane of claim 3, wherein in Formula II at least 50 percent of the R moieties are methyl.

5. The composite membrane of claim 3 or claim 4, wherein in Formula II p is 30 to 1500.

6. The composite membrane of any of claims 3 to 5, wherein in Formula II n is 10 to 2000.

7. The composite membrane of any of claims 3 to 6, wherein in Formula II Z is 2,6-tolylene, 4,4'- methylenediphenylene, 3,3'-dimethoxy-4,4'-biphenylene, tetramethyl-m-xylylene, 4,4'- methylenedicyclohexylene, 3,5,5-trimethyl-3-methylenecyclohexylcne, 1,6-hexamethylene, 1,4- cyclohexylene, 2,2,4-trimethylhexylene, or mixtures thereof.

8. The composite membrane of claim 1, wherein the segmented polydiorganosiloxane copolymer comprises the repeating unit of Formula III:III, wherein: each R1is independently an alkyl, haloalkyl, aralkyl, alkenyl, aryl, or aryl substituted with an alkyl, alkoxy, or halo; each R2is independently an H, alkyl, haloalkyl, aralkyl, alkenyl, aryl, or aryl substituted with an alkyl, alkoxy, or halo, or two R2groups taken together form a ring; each D is independently hydrogen or alkyl or D taken together with G and with the nitrogen to which they are both attached forms a heterocyclic group; each Y is independently an alkylene, aralkylene, or a combination thereof;L is an alkylene, alkenylene, alkynylene, arylene, heteroarylene, heterocyclene, aralkylene, or a bond; each G is an alkylene, heteroalkylene, polydiorganosiloxane, arylene, aralkylene, or a combination thereof; subscript n is a number that is 1 to 1500; subscript p is a number that is at least 1; and subscript q is a number that is 0 to 1000.

9. The composite membrane of any of claims 1 to 8, wherein the segmented polydiorganosiloxane block copolymer has greater than 90% polydiorganosiloxane blocks.

10. The composite membrane of any of claims 1 to 9, wherein the separation layer is selective for carbon dioxide.

11. The composite membrane of any of claims 1 to 10, wherein the separation layer comprises a polyether (co)polymer.

12. The composite membrane of any of claims 1 to 11, wherein the separation layer comprises a poly(ether-block-amide) copolymer.

13. The composite membrane of any of claims 1 to 12, wherein the separation layer comprises a poly(ether-block-amide) copolymer in which the ether is polyethylene oxide or poly(tetramethylene oxide) and the amide is a saturated aliphatic polyamide segment.

14. The composite membrane of any of claims 1 to 13, wherein the separation layer is a first separation layer and the composite membrane further comprises a second separation layer disposed between the gutter layer and the first separation layer.

15. The composite membrane of claim 14, wherein the second separation layer comprises a poly(ether-block-amide) copolymer.

16. The composite membrane of any of claims 1 to 15, further comprising a protection layer disposed on the first separation layer opposite the gutter layer.

17. The composite membrane of claim 16, wherein the protection layer has an average thickness of 10 nanometers (nm) to 400 nm.

18. The composite membrane of claim 16 or claim 17, wherein the protection layer comprises a segmented polydiorganosiloxane block copolymer having greater than 90% polydiorganosiloxane blocks.

19. The composite membrane of any of claims 1 to 18, wherein the segmented polydiorganosiloxane block copolymer is a segmented polydiorganosiloxane polyurea block copolymer or a segmented polydiorganosiloxane polyamide block copolymer.

20. The composite membrane of any of claims 1 to 19, wherein the porous substrate has a first major surface having a) an average pore size of less than 100 nm and b) a porosity of 0.1 to 20 percent.

21. The composite membrane of any of claims 1 to 20, wherein the porous substrate comprises a polymeric material selected from the group consisting of polyacrylonitrile (PAN), polydimethylsiloxane copolymer, polysulfone, cellulose acetate, polyether sulfone (PES), polyvinylidene fluoride (PVDF), polyetherimide (PEI), polyaminosiloxane, polydimethylphenylene oxide (PPO), polyvinylpyridine (PVP), ethylene chlorotrifluoroethylene (ECTFE), polytetrafluoroethylene (PTFE), polyamide, polyethylene, polypropylene, polymethylpentene, cellulose nitrate, polyester, polycarbonate, and polyimide.

22. The composite membrane of any of claims 1 to 21, wherein the gutter layer exhibits an advancing water contact angle of less than 100°.

23. The composite membrane of any of claims 1 to 22, exhibiting a carbon dioxide gas to nitrogen gas selectivity of at least 20 CO2 / N2.

24. The composite membrane of any of claims 1 to 23, exhibiting a carbon dioxide gas permeance of at least 100 gas permeation units (GPU).

25. The composite membrane of any of claims 1 to 24, wherein the gutter layer exhibits an X-ray scattering peak centered between 0.03-0.6 A'1that corresponds to a d spacing of 1 to 20 nm when analyzed by the Small Angle X-ray Scattering Method.

26. The composite membrane of any of claims 1 to 25, further comprising surface modification of the gutter layer that enhances adhesion with separation layer.

27. A method of separating gases, the method comprising:passing a mixture of gases through a composite membrane according to any of claims 1-26, wherein the passing operation comprises passing the mixture of gases through the separation layer prior to the gutter layer.

28. The method of claim 27, wherein the mixture of gases comprises carbon dioxide.

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