Effect of Two Different Mesogens on Liquid-Crystalline Properties of Chiral Side-Chain Liquid-Crystalline Polysiloxanes

摘要

A series of liquid crystalline polysiloxanes were synthesized by cholesteric LC monomer and nematic LC monomer. The chemical structures and liquid-crystalline properties of the monomers and polymers were characterized by various experimental techniques including Fourier transform infrared (FTIR), proton nuclear magnetic resonance spectra (1H-NMR), differential scanning calorimetry (DSC), thermogravimetric analyses (TGA), X-ray diffraction measurements (XRD) and polarizing optical microscopy (POM). All the liquid crystalline polymers showed liquid crystalline properties with wide mesophase temperature ranges. For the polymers bearing only of one nematic LC monomer, it showed nematic phase, while others showed cholesteric phase. With increase the content of nematic LC monomer in the polymers from P1 to P7, the glass transition temperature and the isotropic temperature increased on heating circles. Reflection spectra of cholesteric mesophase of the series of polymers showed that the reflected wavelength shifted to long wavelength with increase content of nematic LC monomer in the polymers in the polymer systems, suggesting that helical pitch (P) become long.