A. Kanazawa et al., EFFECT OF SILOXANE SPACER ON PHOTOCHEMICAL PHASE-TRANSITION BEHAVIOR OF POLYMER LIQUID-CRYSTALS WITH AZOBENZENE MOIETIES IN THE SIDE-CHAIN, Molecular crystals and liquid crystals science and technology. Section A, Molecular crystals and liquid crystals, 300, 1997, pp. 201-218
The effect of flexible siloxane spacers on photochemical phase transit
ion behavior was investigated for polymer liquid crystals (PLCs) with
an azobenzene group as a photoresponsive moiety in which mesogens (azo
benzene and cyanobiphenyl moieties) are attached to the polymer main c
hain through different types of spacers (siloxane and alkyl chains). T
he PLC possessing the siloxane spacer and the non-photoresponsive moie
ty in the same side chain showed a slower response in the photochemica
l liquid-crystalline (LC) to isotropic (I) phase transition than the a
nalog having the siloxane spacer and the photoresponsive moiety in the
side chain. The result indicates that the flexible siloxane spacer st
abilizes the phase structure of the LC phase and depresses the propaga
tion of the perturbation due to trans-cis isomerization of the azobenz
ene in the LC phase. Furthermore, it was also confirmed that the space
r structure did not affect the photoisomerization behavior of the azob
enzene moieties.