SYNTHESIS, CHARACTERIZATION, AND THERMOTROPIC PROPERTIES OF SIDE-CHAIN LIQUID-CRYSTALLINE POLYSILOXANE POLYMERS WITH AN OLIGO(ETHYLENE OXIDE) UNIT IN THE SIDE-CHAIN

A series of new alkene and octenyloxy monomers containing 4'-[oligo(ethylene oxide)]n monomethyl ether 4-biphenyl ether carboxyl benzoate [MS3BDBE(n)] (n = 1 to 3) and 1-(p-methoxydiphenyl)- (carboxyl benzoate) [oligo(ethylene oxide)]n [MS(m+2)BEnDB] (m = 1, 6; n = 1 to 3) as end groups were synthesized. The molecular structure of the monomers was characterized using nuclear magnetic resonance (NMR) spectroscopy. These monomers were grafted onto poly(methylhydrosiloxane)s (PMHS) by the platinum-catalyzed hydrosilylation process. The thermal transition temperatures and mesophase textures of the monomers and the polysiloxane polymers have been determined by differential scanning calorimetry (DSC) and by polarized optical microscopy. The effect of changes in chemical structure on the mesophase properties, glass transition temperature, isotropic temperature, and mesophase texture of the monomers and the polysiloxane polymers is discussed. Polymers PS3BDBEn showed smectic and nematic phases which were not analogous to their precursor nematic monomers MS3BDBEn. Both monomers MS(m+2)BE(n)DB and their polymeric homologous PS(m+2)BE(n)DB did not exhibit mesophase properties. This demonstrated that the polymer effect could not stabilize the mesophase obtained from mesogenic core which contained a flexible oligo(ethylene oxide) unit interconnecting aromatic group. (C) 1995 John Wiley and Sons, Inc.