Synthesis and Thermal and Photoluminescence Properties of Liquid Crystalline Polyacetylenes Containing 4-Alkanyloxyphenyl <i>trans</i>-4-Alkylcyclohexanoate Side Groups

Abstract

Two series of polyacetylenes containing 4-alkanyloxyphenyl trans-4-n-alkylcyclohexanoate were synthesized using [Rh(nbd)Cl]2, MoCl5, and WCl6 as initiators. Polymers 1P−3P, which contain no flexible spacer, show no mesomorphic properties due to the rigid poly(phenylacetylene) backbone. Polymers 4P−9P, which contain three or four methylene units in their spacers, exhibit both SA and Sc phases. X-ray diffraction diagrams reveal that the liquid crystalline polyacetylenes display an interdigitated bilayer structure for the smectic phases. Polymers 4P−9P are photoluminescent, and their emission wavelengths are about 500 nm. The photoluminescence intensity increased dramatically when a liquid crystalline polyacetylene was blended with poly(methyl methacrylate).