Thermotropic Behavior of Syndiotactic Polymethyleneswith ω-[4-(trans-4-Pentylcyclohexyl)phenoxy]alkyloxycarbonylSide Chains.

A seriesof syndiotatic P5CPnpolymethylenes wasprepared with 4-(trans-4-pentylcyclohexyl)phenoxy moieties linkedto each backbone carbon atom via an alkyloxycarbonyl spacer and witheven numbers of alkyl carbons nranging from 2 to14, and their thermotropic behaviors were investigated. The P5CPn, except P5CP2, formed smectic phases in which the rod-likepolymethylene backbones were arranged in rectangular lattices, andthe side-chain mesogens were aggregated into layers parallel to theshorter sides of the rectangular lattices. The packing of the mesogenschanged with decreasing temperature from smectic C-like to smecticI-like (SmI-like) for n= 4–8 and from smecticA-like to SmI-like for n= 10–14. In the SmI-likephases, each mesogen along the main-chain axis was connected to everysixth backbone carbon atom, revealing a correlation between the packingof the mesogens and the main-chain conformation of a 3/2 helix. Conversely,P5CP2 formed a smectic phase with the main chains arranged in rowsand with the mesogens barely aggregated into layers due to the shortspacers. [ABSTRACT FROM AUTHOR]