The influence of lateral substituents on the phase behavior of side-chain liquid crystalline polysiloxanes containing trans-2,5-disubstituted-1,3-dioxane based mesogenic side groups

Abstract

Abstract:The synthesis and characterization of the polysiloxanes containing trans-2,5-disubstituted-l,3-dioxane-based mesogenic side groups were described in this present study. Among three polysiloxanes containing three methylene units in their spacers, one without the lateral substituent exhibited two enantiotropic smectic phases while the other two polymers with a lateral methyl-or methoxy-substituent displayed an enantiotropic nematic phase. For polymers containing alonger spacer length (n _> 4), those without lateral substituent presented two enantiotropic smectic phases while the others containing a lateral substituent showed only an enantiotropic smectic A phase. The lateral substitulion exerted a strong elTect on the mesomorphic properties of the synthesized polymers.

Polysiloxane-Based Side Chain Liquid Crystal Polymers: From Synthesis to Structure–Phase Transition Behavior Relationships

“…Special attention is paid to the effect of the heteroatom (such as O, S) in the spacers and their properties. In regard to the dependence of mesogenic units on phase structures and phase behaviors, in addition to the influence of diverse rigid structures [76,77,78]; the lateral substituents of the mesogenic side groups [79,80,81], the aliphatic tail length of the mesogenic groups [82,83,84,85], the chirality [86,87,88,89] and polarity [90] of the mesogenic groups, and the functionality of the mesogenic groups (such as photo-sensitive property [91,92,93,94], amphiphilic property [95,96], etc.) exerted a strong effect on mesomorphic properties.…”