Induction of Smectic Layering in Nematic Liquid Crystals Using Immiscible Components. 2. Laterally Attached Side-Chain Liquid-Crystalline Poly(norbornene)s and Their Low-Molar-Mass Analogues with Hydrocarbon/Oligodimethylsiloxane Substituents

Abstract

In contrast to their hydrocarbon analogues which exhibit only nematic mesophases, poly{5-[[[2‘,5‘-bis[(4‘‘-(n-(dimethylsiloxyl)alkoxy)benzoyl)oxy]benzyl]oxy]carbonyl]bicyclo[2.2.1]hept-2-ene}s and their low-molar-mass model compounds exhibit smectic C mesophases. Since nematic liquid crystals can be forced into layers by terminating their hydrocarbon substituents not only with fluorocarbon segments but also with flexible siloxane segments, this supports the hypothesis that the smectic mesomorphism of amphiphilic molecules containing linear fluorocarbon segments is due primarily to the immiscibility of the hydrocarbon and fluorocarbon segments, rather than to a shape persistence of “mesogenic perfluoroalkyl rods”. The 2,5-bis[(4‘-(n-(oligodimethylsiloxyl)alkoxy)benzoyl)oxy]toluenes mimic both the phases formed by the polymers and the general temperatures of their transitions and are thereforeexcellent models of the polymers. The 5-{[[2‘,5‘-bis[(4‘‘-(n-(oligodimethylsiloxyl)alkoxy)benzoyl)oxy]benzyl]oxy]carbonyl}bicyclo[2.2.1]hept-2-enes were polymerized by ring-opening metathesis polymerization in THF at room temperature using Mo(CHCMe2Ph)(N-2,6-iPr2Ph)(OtBu)2 as the initiator.