Synthesis and properties of side chain cholesteric liquid-crystalline polyacrylates containing two mesogenic groups

The synthesis of side chain cholesteric liquid-crystalline polymers containing both 4-cholesteryl-4'-acryloyloxybenzoate (M-I) and 4-methoxyphenyl-4'-acryloyloxybenzoate (M-II) mesogenic side groups is described. The chemical structures of the obtained monomers and polymers are confirmed by Fourier transform infrared (FTIR) spectroscopy. The phase behavior and optical properties of the synthesized monomers and polymers were investigated by polarizing optical microscopy (POM), differential scanning calorimetry (DSC), and thermogravimetric analyses (TGA). The homopolymer IP reveals a cholesteric phase and VIIP displays a nematic phase. The copolymers IIP-VIP exhibit, respectively, cholesteric oily-streak texture and focal-conic texture. The fixation of the helical pitch and oily-streak texture of the cholesteric phase is achieved by quenching, and polymer films with different reflection colors are obtained. The experimental results demonstrate that the glass transition temperature (T-g) and the melting temperature (T-m) of the copolymers IIP-VIP decrease, whereas the isotropization temperature (T-i) and the mesomorphic temperature range (DeltaT) increase with increasing content of mesogenic M-II units. TGA results indicate that the temperatures at which 5% mass loss occurred (T-5wt%) of all copolymers are >245degreesC. (C) 2003 Wiley Periodicals, Inc.