Mechanical perturbation induced molecular alignments in a side-chain liquid crystalline polyacetylene, poly{10-[4-(4 '-methoxyphenoxycarbonyl)phenoxycarbonyl]-1-decyne}

A new liquid crystalline polyacetylene containing a phenyl benzoate mesogen (5) is synthesized, whose mesomorphic properties are found to be easily "t unable" by simple mechanical perturbation. The polymerization of 10-[4-(4'- methoxyphenoxycarbonyl)phenoxycarbonyl]-1-decyne (4) initiated by the WCl6- Ph4Sn/dioxane complex yields polymer 5 with a M-w of 28400. The molecular s tructure of 5 is characterized by NMR, IR, and UV spectroscopy and its liqu id crystalline behavior is investigated by DSC, POM, and XRD analysis. Upon mechanical perturbation, 5 exhibits unusual agitation-induced high-strengt h disclinations, shear-induced inversion walls, and solidification-induced banded textures. Such phenomena have been observed in the main-chain liquid crystalline polymers with rigid backbones, but have seldom been reported f or the side-chain liquid crystalline polymers with flexible backbones, sugg esting that the rigid polyacetylene backbone of 5 plays a constructive role in inducing the novel molecular alignments.