Synthesis and characterization of side chain cholesteric liquid crystalline polymers containing isosorbide as a chiral centre

A series of new side chain cholesteric liquid crystalline polysiloxanes was synthesized by grafting copolymerization of a mesogenic monomer (M-1) and a chiral monomer (M-2). The chemical structures of the monomers and polymers obtained were confirmed by FTIR, and H-1 and C-13 NMR spectroscopy. The mesomorphic properties were investigated by differential scanning calorimetry, polarizing optical microscopy, and X-ray diffraction. The influence of the content of the chiral unit on phase behaviour of the polymers is discussed. Monomer M-1 showed nematic and smectic phases on cooling. The polymers P-1 and P-2 showed a nematic phase, P-3 - P-5 showed cholesteric Grandjean texture, and P-6 and P-7 exhibited smectic short-rod texture. The polymers containing more than 7.2 mol% and less than 28.6 mol% of the chrial unit showed an induced cholesteric phase. Experimental results demonstrated that the glass transition, melting and clearing temperatures decreased with increasing content of the chiral unit.