NANO-STRUCTURED, SEMICRYSTALLINE POLYMER FOAMS

Semicrystalline polymers gelled from thermally quenched semidilute sol utions can, in some cases, be supercritically dried to produce nano-st ructured foams of exceedingly high specific surface area. This article investigates the nano-morphology of these semicrystalline foams. The common morphological feature that these systems display in small-angle scattering can be described by uncorrelated lamellar platelets. The m orphological details, which can be obtained using microscopy and small -angle scattering, indicate that these low-density systems occupy a mo rphological niche between polymeric crystallites from dilute solutions , and spherulitic crystals derived from concentrated solutions and mel ts. Because these crystalline morphologies occur in concentration rang es between dilute and concentrated, they may offer simple insight into the mechanisms available for distortion of ideal, dilute-solution-der ived crystallites as polymer concentration is increased. Several mecha nisms for the observed distortions are proposed. (C) 1996 John Wiley & Sons, Inc.