Patent ID: 7644825

Claim:
A membrane having an open-nanoporous morphology producible by shaping a polymer blend by melt processing, loading the polymer blend with a foaming gas at a superatmospheric pressure, foaming the foaming gas loaded polymer blend at a gas concentration within the polymer blend above a critical gas concentration and at a temperature below a critical temperature, but above the glass transition temperature of the polymer blend/gas mixture and finally stabilizing into a foam structure, said polymer blend being a homogeneous hydrophilic polymer blend having a hydrophilicity that allows spontaneous wetting of the membrane surface with blood, plasma, or other aqueous solutions, comprising components including, at least one hydrophilic polymer and at least one hydrophobic polymer, wherein the polymer blend has a solubility relating to the used foaming gas above the critical gas concentration, and the glass transition temperature of the components of the polymer blend are within 150° C. of one another.