Microporous polymeric foams and microtextured surfaces

A foam comprising:

• a highly uniform continuous matrix including an organic crystalline thermoplastic polymer and highly uniform, continuous, open-cell pores dispersed in said matrix, the foam produced by a process comprising the steps of:
• melting the polymer with a solid crystalline additive composition to form an isotropic solution, said additive composition having a melting point above 25.degree. C. and having at least one of the following physical characteristics:
• (i) a sublimation temperature between about 25.degree. C. and the lower of the degradation, melting or glass transition temperature of the polymer, and
• (ii) extractability by solvents which are not solvents for the polymer;
• solidifying the isotropic solution such that the additive composition and the polymer separate by essentially simultaneous crystallization to produce a foam precursor containing crystals of the additive composition;
• and
• removing crystals of the additive composition from the foam precursor to produce a highly uniform continuous, open-cell foam, wherein the removing is accomplished by a process selected from the group consisting of solvent extraction, sublimation and a combination of solvent extraction and sublimation.