Morphology of a Phase Separated and a Molecular Composite 30%PBT/70%ABPBI Polymer Blend

摘要

Scanning electron microscopy (SEM), transmission electron microscopy (TEM), analytical electron microscopy (AEM), and wide-angle x-ray diffraction (WAXD) were used to examine a polymeric blend of rigid-rod poly(p-phenylene benzobisthiazole), PBT, and semi-flexible coil poly(2,5(6)benzimidazole), ABPBI. When fiber and film were processed from a solution where the total polymer concentration of a 30% PBT/70% ABPBI blend was greater than a critical concentration, large-scale phase separation occurred and SEM images showed 0.1 micron to 4 micron ellipsoidal particles in a ductile matrix. TEM and AEM indicated these ellipsoids were chiefly composed of aggregates of well-oriented PBT crystallites with lateral dimensions of about 10 nm, while the matrix material was chiefly ABPBI. If the total polymer concentration of a 30% PBT/70% ABPBI blend was less than a critical concentration, the solution was optically homogeneous. During processing of the homogeneous solution into fiber and film, large-scale phase separation was inhibited by rapid coagulation in a water bath. Fiber and film processed in this manner did not show any large-scale phase separation when examined by SEM and TEM. After heat treatment this fiber and film were found to contain crystallites with lateral dimensions no larger than 3 nm, as determined by WAXD and TEM. Selected area electron diffraction and WAXD indicated crystallites of both PBT and ABPBI were present.