MULTIDIMENSIONAL BENZOBISOXAZOLE RIGID-ROD POLYMERS .2. PROCESSING, CHARACTERIZATION, AND MORPHOLOGY

A high-torque rheometer was used to facilitate the polycondensation of 4-[5-amino-6-hydroxybenzoxazol-2-yl]benzoic acid (ABA) with trimesic acid and 1,3,5,7-tetrakis( 4-carboxylatophenyl)adamantane to yield two -and three-dimensional benzobisoxazole polymers, respectively. Althoug h the resultant polymer dopes exhibited improved homogeneity compared to polymer dopes previously prepared in glassware, improved polymer so lution viscosities were not achieved. Fibers spun from the two- and th ree-dimensional polymers did not show a significant increase in compre ssive strength compared to fibers of the linear or one-dimensional ben zobisoxazole polymer derived from the homopolymerization of ABA. Morph ological studies of the polymer fibers and films by wide-angle X-ray s cattering and scanning electron microscopy strongly indicated more lat eral disorder and a more isotropic character for the three-dimensional structures compared to the one-dimensional structures. (C) 1997 John Wiley & Sons, Inc.