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Abstract
A series of smectic liquid crystal polymers with a polysiloxane backbone and Schiff s base side-chains is presented.
In a three-step procedure, hydroxy-terminated Schiff s bases were first prepared and then converted to allyloxy-terminated derivatives. Only few of the resulting monomers were liquid crystals, even though all were potentially mesomorphic.
When attached to a polysiloxane backbone via a 3-carbon spacer, all resulting polymers were smectic. Where comparisons were possible, the mesophase ranges for the polymers were greater than those for the corresponding side-chain precursors.
Interesting trends were observed in the effect of the length of the alkyl and alkoxy terminal substituent on the liquid crystal properties. The chloro-terminated side-chain precursors did not exhibit liquid crystal properties, but gave the widest mesomorphic range polymers. The high transition enthalpies for the mesomorphic-isotropic transition are indicative of a smectic mesophase. The transition temperatures and entropies for the smectic-isotropic transitions for an alkoxy terminated series show odd-even alternations.