LIQUID-CRYSTAL POLYMERS - EVIDENCE OF HAIRPIN DEFECTS IN NEMATIC MAINCHAINS, COMPARISON WITH SIDE-CHAIN POLYMERS

This article describes the conformation of two species of liquid cryst alline polymers as revealed by small angle neutron scattering. The res ults obtained with side chain polymers are recalled. The procedure use d to analyze the scattering data of main chains in the nematic phase i s reported in this paper. It permits a demonstration of the existence of hairpins. Comparison of both polymer species shows that in the isot ropic phase, the two polymers adopt a random coil conformation. In the nematic phase, the conformations are very different; the side chains behave as a melt of penetrable random coils whereas the main chains be have as a nematic phase of non penetrable cylinders.