the present invention provides a microporous material or a membrane in which the membrane includes an azlactone moiety which is blended with or grafted to a thermoplastic polymer to provide a porous material having an internal structure characterized by a multiplicity of spaced , randomly disposed , non - uniform shaped , equiaxed particles of the polyazlactone polymer / thermoplastic polymer blends or the azlactone - graft copolymer . each of the adjacent particles throughout the material are separated from one another to provide said material with a network of interconnected micropores and each of the particles are connected to each other by a plurality of fibrils . in addition to unmodified azlactone membranes , membranes which have been modified by subsequent reaction of the azlactone moiety with a suitable nucleophile are also included within the scope of the present invention . preferred nucleophiles capable of reacting with an azlactone membrane of this invention include biologically significant nucleophiles such as amines , thiols and alcohols as well as amino acids , nucleic acids and proteins .