Abstract
A series of new cholesteric liquid-crystalline polysiloxanes (P1–P5) derived from menthyl groups were synthesized. The chemical structures of the monomers and polymers were characterized with Fourier transform infrared, 1H-NMR, 13C-NMR, and elemental analyses. The mesomorphic properties and thermal behavior were investigated with differential scanning calorimetry, polarizing optical microscopy, thermogravimetric analysis, and X-ray diffraction measurements. The influence of the polymer structure on the thermal behavior was discussed. The monomer diosgeninyl 4-allyloxybenzoate exhibited a typical cholesteric oily-streak texture and a focal-conic texture. Polymers P1–P5 showed thermotropic liquid-crystalline properties. P1 displayed a smectic fan-shaped texture, P2–P5 showed a cholesteric Grandjean texture, and P6 and P7 did not show mesomorphic properties. The experimental results demonstrated that the glass-transition temperature and the clearing temperature decreased, and the mesomorphic properties weakened with an increasing concentration of menthyl units. Moreover, P1–P5 exhibited wide mesophase temperature ranges and high thermal stability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:5559–5565, 2006
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