Polymorphism of Smectic Phases with Smectic a Morphology
A number of 4-n- alkoxybenzylidene-4′-aminopropiophenones with different alkoxy groups have been synthesized. Many of these compounds show two smectic phases, both of which have a morphology identical to that of the classical smectic A of Sackmann and Demus. Both the phases show step drops, focal-conic structure and homeotropic form. No apparent change either in the mechanical or optical properties is observable at the transition temperature of these two phases. The heats of transition for smectic 1 — smectic 2 is much lower than what has been reported for smectic A — smectic B and higher than smectic A — smectic C. We propose a simple model for the phase transition based on the polar ordering of the molecules. Electric field effects are also presented.
KeywordsDifferential Thermal Analysis Phase Transition Temperature Nematic Phase Alkoxy Group Liquid Crystal Phasis
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