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