Synthesis, structure and mesomorphic properties of side-chain chiral liquid crystalline polysiloxanes based on (S)-(+)-2-methyl-1-butanol derivatives

The synthesis of five chiral liquid crystalline monomers (M-1-M-5) and their corresponding side-chain polymers (P-1-P-5) based on (S)-(+)-2-methyl-1-butanol derivatives is described. The chemical structures of the monomers were confirmed by FT-IR. H-1 NMR, and elemental analyscs. The structure-property relationships of the monomers and polymers obtained are discussed. The mesomorphic properties were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), polarizing optical microscopy (POM), and X-ray diffraction (XRD) measurements. All monomers showed a cholesteric phase. For M-2, M-3, and M-5, besides a cholesteric phase and a smectic A (SA) phase, M-2 also revealed an enantiotropic chiral smectic C (S*(C)) phase and a monotropic smectic B (SB) phase, and M-3 also showed a SB phase. The C polymers P-1-P-5 exhibited a SA phase, moreover, P-2, P-3 and P-5 also revealed a SL phase. The experimental results demonstrated that a flexible siloxane backbone and a long flexible spacer tended to exhibit a low glass transition temperature, high thermal stability, and wide mesophase:ise temperature range. (C) 2007 Elsevier Ltd. All rights reserved.