Vinylsilanes as monomers for side chain polymer liquid crystals

A series of novel side chain polymers-silylated polyethylenes were prepared containing 4'-methoxyphenyl-4-(omega-alkenyloxy)benzoate mesogenic groups of the general formula {-CH2-CH[SiMe2(CH2)(m)OC6H4C(O)OC6H4OMe]}(n)-, where m = 4, 5, 8, 11. The ones having five and eight carbon atoms in the alkane moiety of a flexible spacer proved to be liquid crystalline, independent of molecular weight (DP = 75, 230). Alternative synthetic pathways have been described starting with anionic polymerization of Me(3)SiVi or Me(2)PhSiVi in the presence of BuLi, followed by functionalization of side silyl group to give reactive Si-H bonds and hydrosilylation of terminal, mesogenic alkenes. The properties of Liquid crystal polyethylenes were compared with those of side chain polycarbosilanes of similar structure. The advantage of polyethylenes, while preserving all important features of polycarbosilanes, is shown by their broad temperature range of mesophase formation and the economically attractive synthesis.