Synthesis and properties of liquid crystalline conjugated disubstituted polyacetylene containing cyanoterphenyl mesogenic pendant

Abstract

Novel acetylene monomers containing cyanoterphenyl groups, namely, 4-[(4′-cyano-4-terphenylyl)oxy]-1-butyl-1-butyne M(1) and 3-[(4′-cyano-4-terphen-ylyl)oxy]-1-phenyl-1-proyne M(2) are synthesized. M(1) was polymerized with WCl 6–PhSn 4 catalyst successfully to give the liquid crystalline conjugated disubstituted polyacetylene containing cyanoterphenyl mesogenic pendant P(1). Polymerization of monomer M(2) was carried out in a series of different solution, but did not obtain any product. The results indicate that the stereoeffect of the bulky cyanoterphenyl group and phenyl seems to inhibit the reaction. The structures and properties of the disubstituted polyacetylene P(1) and monomers were characterized and evaluated with nuclear magnetic resonance, infrared spectroscopy, thermogravimetry, differential scanning calorimetry, polarized optical microscopy, ultraviolet spectroscopy, and photoluminescence. The monomers show enantiotropic smectic phases in the heating and cooling processes, while the polymer P(1) exhibits a nematic phase when observed with a polarizing optical microscope. The existence of the chromophoric cyanoterphenyl core endows the monomers with high photoluminescence, and the polymer P(1) prepared from M(1) can emit a strong UV light of 411 nm.