N-SUBSTITUTED POLY(P-PHENYLENE TEREPHTHALAMIDE) FILM - SURFACE CHARACTERISTICS AND LIQUID-CRYSTAL ALIGNMENT WITH HIGH PRETILT ANGLES

N-Substituted poly(p-phenylene terephthalamide)s (PPTA) with various s ubstituents in their side chains have been synthesized, and the surfac e characteristics of their films studied. N-Substituted PPTA showed hi gh thermal stability and solubility in organic solvents, and the thin films, prepared by a casting method, showed a smooth surface with surf ace free energies of 30-50 erg cm-2. After rubbing with rayon fibres, the films easily aligned nematic liquid crystals at their surfaces. Pr etilt angles induced at the surface of benzyl- and 4-methylbenzyl-subs tituted PPTAs with a high degree of substitution, were 4.6 and 8.1-deg rees, respectively. A rigid side-chain structure and a high degree of substitution are suggested as being more important than low surface fr ee energy for inducing a high pretilt angle.