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A series of syndiotatic P5CPn polymethylenes was prepared with 4-(trans-4-pentylcyclohexyl)phenoxy moieties linked to each backbone carbon atom via an alkyloxycarbonyl spacer and with even numbers of alkyl carbons n ranging from 2 to 14, and their thermotropic behaviors were investigated. The P5CPn, except P5CP2, formed smectic phases in which the rod-like polymethylene backbones were arranged in rectangular lattices, and the side-chain mesogens were aggregated into layers parallel to the shorter sides of the rectangular lattices. The packing of the mesogens changed with decreasing temperature from smectic C-like to smectic I-like (SmI-like) for n = 4–8 and from smectic A-like to SmI-like for n = 10–14. In the SmI-like phases, each mesogen along the main-chain axis was connected to every sixth backbone carbon atom, revealing a correlation between the packing of the mesogens and the main-chain conformation of a 3/2 helix. Conversely, P5CP2 formed a smectic phase with the main chains arranged in rows and wi...

A series of syndiotactic polymethylenes having an alkyloxycarbonyl side chain, with the alkyl carbon numbers 2, 6, 12, and 18 at every main-chain carbon atom, was synthesized by rhodium complex-catalyzed stereo-selective polymerization. Differential scanning calorimetry (DSC) and X-ray diffraction revealed that all polymers formed thermotropic liquid crystalline phases. The polymethylene having an ethoxycarbonyl side chain formed a nematic phase whereas those having hexyloxy-, dodecyloxy-, and octadecyloxy-carbonyl side chains formed hexagonal columnar phases. The tendency of these polymers to form liquid crystalline phases is due to the rod-like helical conformation in the polymer backbone, which is estimated to be seven units per two turns (7/2) with a unit height of 1.05 4 A along the helix axis.