MOLECULAR COMPOSITE FILMS FROM POLYBENZOXAZOLE AND CROSS-LINKED POLYMER MATRICES

Films consisting of a rigid-rod polymer and thermoset resin matrixes m ere prepared. Poly{(benzo[1,2-d : 5,4-d']bis(oxazole-2,6-diyl))-1,4-ph enylene} (PBO) in polyphosphoric acid (PPA) was blended with 2,6-bis(4 -benzocyclobutene) benzo[1,2-d : 5,4-d']bis(oxazole) (1), and films we re extruded from these solutions. The coagulated films were soluble in methanesulfonic acid (MSA). After heat treatment at 300 degrees C, th e films became insoluble in MSA. Crosslinked films were homogeneous an d did not show phase segregation between the two components. These wer e composite films at the molecular level. Transmission electron micros copy (TEM) showed enhanced interlayer integrity and reduced microfibri l separation for the molecular composite films as compared to normal P BO film. These films had significantly better torsion and tension dela mination resistance. The incorporation of a second component did not s acrifice the tensile properties of PBO film. Thermal stability of thes e composite films was only slightly lower than that of normal PBO film . (C) 1997 John Wiley & Sons, Inc.