Rigid Rod Polymers with Flexible side Chains: A New Class of Liquid Crystalline Polymers

Abstract

A series of fully aromatic polyesters, polyamides, and polyimides bearing n-alkoxy side chains (n=2–18) have been investigated by optical microscopy, X-ray analysis and DSC. All members of these series have a rigid backbone and exhibit a decreasing melting range with increasing length of the side chains. The polyester with short side chains (n=2–6) form nematic melts. Longer side chains lead to the observation of a novel layered mesophase for all systems under consideration here. There is a linear relationship between the length of the side chains and the layer spacing observed in the mesophase. All findings can be explained by assuming a packing model with interdigitated side chains.