Flexible Template-Directed Microporous Partially Pyrolyzed Polymeric Membranes

Abstract

This invention describes a new concept of flexible template-directed microporous partially pyrolyzed polymeric membranes which have greatly improved performance in separation of gas pairs compared to their precursor polymeric membranes. Organic hosts, such as crown ethers, cyclodextrins (CDs), calixarenes (CXs), and spherands, or polymeric additives, such as poly(ethylene glycol) (PEG) and polyvinylpyrrolidone (PVP) were used as the micropore-forming templates. Micropore-forming template/polymer blend membranes comprising organic micropore-forming templates embedded in a polymer matrix were prepared by dissolving the organic micropore-forming templates in the polymer solution followed by solution-casting and solvent evaporation or solvent exchange. Low-temperature selectively pyrolyzing micropore-forming templates in the micropore-forming template/polymer blend membranes at a nitrogen flow resulted in the formation of flexible microporous partially pyrolyzed polymeric membranes.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph illustrating the concept of flexible template-directed microporous partially pyrolyzed polymeric membranes.

FIG. 2 shows the chemical structure of α-, β- and γ-cyclodextrins (α-, β- and γ-CDs).

FIG. 3 shows the synthesis of acetyl-β-CD.

FIG. 4 shows the thermogravimetric analysis (TGA) curve of acetyl-β-CD.

FIG. 5 shows the TGA curve of pure Matrimid®.

FIG. 6 shows the effect of the applied CO₂ pressures on the relative CO₂ permeability in (a) Matrimid® and (b) 30% acetyl-β-CD/Matrimid® at 425° C. and 2 hours dense films at 50° C.

Claims

1. A flexible template-directed microporous partially pyrolyzed polymeric membrane comprising organic micropore-forming templates embedded in a polymer matrix.

2. The polymeric membrane of claim 1 wherein said organic micropore-forming templates are selected from the group consisting of crown ethers, cyclodextrins, calixarenes, and spherands, poly(ethylene glycol)s, polyvinylpyrrolidone, poly(acrylic acid), poly(ethylene oxide)s (PEO), dendritic PEO, hyperbranched amine-terminated PEO, poly(propylene oxide)s (PPO), co-block-poly(ethylene oxide)-poly(propylene oxide)s (PEO-PPO), tri-block-poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide)s (PPO-PEO-PPO), poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) bis(2-aminepropyl ether) (PAPE), linear and star-shaped poly(caprolactone).

3. The polymeric membrane of claim 1 wherein said polymer matrix comprises at least one polymer selected from the group consisting of polymer is selected from the group consisting of polysulfones; poly(styrenes), styrene-containing copolymers, polycarbonates; cellulosic polymers, polyamides and polyimides, polyethers; poly(arylene oxides), poly(esteramide-diisocyanate); polyurethanes; polyesters, polysulfides; polymers from monomers having alpha-olefinic unsaturation, polyvinyls, polyallyls; poly(benzobenzimidazole); polyhydrazides; polyoxadiazoles; polytriazoles; poly (benzimidazole); polycarbodiimides; polyphosphazines; and interpolymers, including block interpolymers containing repeating units from the above such as terpolymers of acrylonitrile-vinyl bromide-sodium salt of para-sulfophenylmethallyl ethers; and grafts and blends containing any of the foregoing and substituted polymers having as substituents halogens such as fluorine, chlorine and bromine; hydroxyl groups; lower alkyl groups; lower alkoxy groups; monocyclic aryl; and lower acyl groups.

4. A process for gas separation using the flexible template-directed microporous partially pyrolyzed polymeric membrane of claim 1 comprising contacting a mixture of gases on one side of said flexible template-directed microporous partially pyrolyzed polymeric membrane to cause said at least one gas to permeate the mixed matrix gas separation membrane; and removing from a side opposite to said one side of the flexible template-directed microporous partially pyrolyzed polymeric membrane a permeate gas composition comprising a portion of said at least one gas which has permeated said mixed matrix gas separation membrane.

5. A method of making a flexible template-directed microporous partially pyrolyzed polymeric membrane comprising combining a polymer and a micropore-forming template and then heating the polymer and micropore-forming template to a low-temperature pyrolysis.

6. The method of claim 5 wherein said polymer and said micropore-forming template are combined by mixing followed by solution-casting of said flexible template-directed microporous partially pyrolyzed polymeric membrane.

7. The method of claim 5 wherein said polymer is thermally stable up to about 450° C.

8. The method of claim 5 wherein said polymer is selected from the group consisting of polysulfones; poly(styrenes), styrene-containing copolymers, polycarbonates; cellulosic polymers, polyamides and polyimides, polyethers; poly(arylene oxides), poly(esteramide-diisocyanate); polyurethanes; polyesters, polysulfides; polymers from monomers having alpha-olefinic unsaturation, polyvinyls, polyallyls; poly(benzobenzimidazole); polyhydrazides; polyoxadiazoles; polytriazoles; poly (benzimidazole); polycarbodiimides; polyphosphazines; and interpolymers, including block interpolymers containing repeating units from the above such as terpolymers of acrylonitrile-vinyl bromide-sodium salt of para-sulfophenylmethallyl ethers; and grafts and blends containing any of the foregoing and substituted polymers having as substituents halogens such as fluorine, chlorine and bromine; hydroxyl groups; lower alkyl groups; lower alkoxy groups; monocyclic aryl; and lower acyl groups.

9. The method of claim 5 wherein said organic micropore-forming templates are selected from the group consisting of crown ethers, cyclodextrins, calixarenes, and spherands, poly(ethylene glycol)s, polyvinylpyrrolidone, poly(acrylic acid), poly(ethylene oxide)s (PEO), dendritic PEO, hyperbranched amine-terminated PEO, poly(propylene oxide)s (PPO), co-block-poly(ethylene oxide)-poly(propylene oxide)s (PEO-PPO), tri-block-poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide)s (PPO-PEO-PPO), poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) bis(2-aminepropyl ether) (PAPE), linear and star-shaped poly(caprolactone).