Synthesis and characterization of side-chain cholesteric liquid crystalline polysiloxanes containing diosgeninyl groups

New cholesteric liquid crystalline polysiloxanes derived from diosgeninyl groups were synthesized. The chemical structures of the monomers and polymers obtained were confirmed by element analyses, Fourier transform infrared, proton nuclear magnetic resonance and carbon-13 nuclear magnetic resonance spectra. Their mesogenic properties were investigated by polarizing optical microscopy, differential scanning calorimetry, thermogravimetric analysis, and X-ray diffraction measurements. Monomer M-1 exhibited monotropic cholesteric focal-conic texture, and M-2 showed enantiotropic cholesteric phase. Homopolymers showed smectic phase and copolymers showed cholesteric phase. The experimental results demonstrated that the phase behavior and the mesophase temperature ranges of the polymers obtained were affected by the copolymer composition.