Mesomomorphism enhancement of modified side-chain liquid-crystalline polysiloxanes by copolymerization

The liquid-crystalline (LC) monomer 4-allyoxybenzoyloxy-4'-buthylbenzoyloxy-p-phenyl (M-1), whose LC phase appeared at lower temperatures, from 137 to 227 degrees C, and the modified mesogenic monomer 4-allyoxybenzoyloxy-4'-methyloxybenzoyloxy-p-biphenyl (M-2), whose LC phase appeared at higher temperatures, from 185 to 312 degrees C, were prepared. A series of side-chain LC polysiloxanes containing M-1 and M-2 were prepared by graft copolymerization. Their LC properties were characterized by differential scanning calorimetry, thermogravimetric analysis, polarizing optical microscopy, and X-ray diffraction. The results show that the introduction of the modified mesogenic monomer M-2 into the polymeric structure caused an additional increase in the clearing point (isotropic transition temperature) of the corresponding polysiloxanes, compared with unmodified polysiloxanes, but did not significantly affect the glass-transition temperature. Moreover, the modified polysiloxanes exhibited nematic phases as the unmodified polymer did. (c) 2005 Wiley Periodicals, Inc.