Crystal‐amorphous interphases in binary semicrystalline/amorphous polymer blends

Abstract

Crystal‐amorphous interphases in binary polymer blends that are miscible in the melts but phase separate due to crystallization of one polymer have been investigated theoretically by employing lattice models and experimentally by dielectric spectroscopy measurements. Theory predicts the extent of tight adjacent re‐entry to depend strongly on the energy Eq disfavoring the tight‐fold conformations and to increase slightly with favorable interaction energy ‐ χAB in the blends. The interfacial region of varying composition is predicted to depend strongly on χAB, with the interfacial thickness varying with the reciprocal of |χAB|1/2. Therefore, in the limit χAB → 0 the amorphous polymer, which is miscible in the melt, is predicted to be completely excluded from the interlamellar region, in agreement with experimental results. Dielectric relaxation experiments on semicrystalline blends of poly(vinylidene fluoride) (PVDF) with poly(methyl methacrylate) (PMMA) or poly(vinyl pyrrolidone) (PVP) show the existence of nearly pure PVDF interphase which is not penetrated by PMMA or PVP, despite their strongly favorable interactions with PVDF. These experimental results are discussed and compared with theoretical predictions. Copyright © 1991 Hüthig & Wepf Verlag