Preparation of porous substrates having well defined morphology
First Claim
1. A method of making a microporous membrane having a preselected pore structure, the diameters of the pores being within a preselected range, the method comprising:
- a. providing a solution of polymer (A) in an organic solvent, said polymer (A) having at least about 5% by weight of one or more water-soluble groups on its polymer chain or pendant to the backbone of the polymer (A) and also having one or more functional groups capable of reacting, complexing or polymerizing with polymer (B);
b. providing a solution of a polymer (B) in an aqueous solution which is immiscible in said organic polymer (A) solution, said polymer (B) having at least about 5% by weight of at least one functional group which can react, complex, or polymerize with polymer (A), or, said polymer (B) is capable of coagulating in the presence of polymer (A);
c. uniformly dispersing the organic polymer (B) solution in the water-soluble polymer (A) solution to form a multiplicity of micro-spherical droplets of the polymer (A) solution enveloped by a skin composed of the product of reaction of polymers (A) and (B) or the coagulated polymer (B), said polymer (A) solution droplets being uniformly dispersed within a continuous phase comprised of said organic polymer (B) solution;
d. evaporating the organic solvent to form a honeycomb-like structure comprised of said micro-spherical droplets uniformly dispersed within and held together by a solid continuous phase of said polymer (B); and
e. dehydrating the honeycomb-like structure which cracks the exposed surfaces of the micro-spherical droplets and forms the microporous membrane comprised of a solid continuous phase of polymer (B) having a network of pores uniformly dispersed therein, with no overlapping pores, the pores at the surface having preselected sizes between about submicron and about 10 microns in diameter.
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Abstract
A membrane of defined pore structure and controlled pore diameter and a method of preparing the membrane which comprises dispersing in a water soluble polymer solution (A) an organic polymer solution (B), the water-soluble polymer solution (A) being a non-solvent for the polymer solution (B), to form micro-spherical droplets of the polymer solution (A) which are enveloped by a solid phase consisting of a coagulated or cross-linked polymer solution (B); evenly casting the dispersion on a flat surface; and evaporating the solvent for the polymer solution (B) to form a microporous membrane comprised of the polymer (B), the porosity, pore size, and void volume of the microporous membrane being a function of the polymer (A) concentration, the microsphere dimensions and the temperature and evaporation rate. The water-soluble polymer (A) is selected from polyethyleneimine, gelatin, polyvinyl-pyrrolidone, polyvinyl pyridinium halide, polyacrylic acid, polyhydroxyethylmethacrylate (HEMA), dextran, or polyvinyl acetate. The continuous phase polymer (B) is selected from a brominated polyphenylene oxide, polyphenylene oxide, polyacetic acid, polystyrene, polyglycol acrylate (PGA), polymethylmethacrylate, cellulose acetate, polyvinyl acetate, polycarbonate and polyvinylidene fluoride.
64 Citations
21 Claims
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1. A method of making a microporous membrane having a preselected pore structure, the diameters of the pores being within a preselected range, the method comprising:
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a. providing a solution of polymer (A) in an organic solvent, said polymer (A) having at least about 5% by weight of one or more water-soluble groups on its polymer chain or pendant to the backbone of the polymer (A) and also having one or more functional groups capable of reacting, complexing or polymerizing with polymer (B); b. providing a solution of a polymer (B) in an aqueous solution which is immiscible in said organic polymer (A) solution, said polymer (B) having at least about 5% by weight of at least one functional group which can react, complex, or polymerize with polymer (A), or, said polymer (B) is capable of coagulating in the presence of polymer (A); c. uniformly dispersing the organic polymer (B) solution in the water-soluble polymer (A) solution to form a multiplicity of micro-spherical droplets of the polymer (A) solution enveloped by a skin composed of the product of reaction of polymers (A) and (B) or the coagulated polymer (B), said polymer (A) solution droplets being uniformly dispersed within a continuous phase comprised of said organic polymer (B) solution; d. evaporating the organic solvent to form a honeycomb-like structure comprised of said micro-spherical droplets uniformly dispersed within and held together by a solid continuous phase of said polymer (B); and e. dehydrating the honeycomb-like structure which cracks the exposed surfaces of the micro-spherical droplets and forms the microporous membrane comprised of a solid continuous phase of polymer (B) having a network of pores uniformly dispersed therein, with no overlapping pores, the pores at the surface having preselected sizes between about submicron and about 10 microns in diameter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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- 14. A microporous membrane having a preselected pore structure, the diameter of the pores being within a preselected range, said membrane comprised of a solid continuous phase of polymers (A) and (B) configured to have a bee-hive morphology defining a network of pores, with no overlapping pores, the pores at the surface having preselected sizes between submicron and about 10 microns in diameter said polymer (A) having at least about 5% by weight of one or more water-soluble groups on its polymer chain or pendant to its back-bone and also having one or more functional groups capable of reacting, complexing or polymerizing with polymer (B), and said polymer (B) having at least about 5% by weight of at least one functional group which can react, complex or polymerize with polymer (A), or said polymer (B) being capable of coagulating in the presence of polymer (A).
Specification