Design of molecular architectures for polymeric mesophase formation

Abstract

Based on the tendency of low molar mass liquid crystals composed of extended mesogens symmetrically disubstituted with long n ‐alkoxy substituents to exhibit smectic C mesophases, we have proposed that SCLCPs with laterally attached (vs. terminally attached) mesogens offer an ideal architecture for obtaining s C* mesophases. In particular, mesogens that typically form the desirable s C* ‐n phase sequence can be laterally attached to the polymer backbone through a chiral spacer, which should result in high values of spontaneous polarization. Not only are we using mesogens which exhibit s C* ‐n phase sequences, we are also attempting to induce smectic layering into systems which typically form nematic mesophases by using immiscible hydrocarbon/fluorocarbon components and electron‐donor‐acceptor interactions. Thus far, the thermotropic behavior of poly{5‐[[[2', 5'‐bis[(3″‐fluoro‐4″‐dimethoxyphenyl)ethynyl]benzyl]oxy]carbonyl[2.2.1]hept‐2‐ene]s and poly(5‐[[[2',5'‐bis[(3″‐fIuoro‐4″‐methoxybenzoyl)oxy]benzyl]oxy]carbonyl]‐bicyclo[2.2.1]hept‐2‐ene)s correspond to that of their low molar mass analogs. Preliminary results demonstrate that smectic layering is successfully induced in 2,5‐bis[(4'‐ n ‐alkoxybenzoyl)oxy]toluenes and polynorbornenes with laterally attached 2,5‐bis[(4'‐ n ‐alkoxybenzoyl)oxy]benzyl mesogens by terminating the n ‐alkoxy substituents with perfluorinated segments.