Synthesis and phase behavior of chiral side-chain liquid-crystalline polysiloxanes containing two mesogenic groups

The synthesis of chiral side-chain liquid-crystalline polysiloxanes containing both cholesteryl undecylenate (M_I) and 4-allyloxy-benzoyl-4-(S-2-ethylhexanoyl) p-benzenediol bisate (M_II) mesogenic side groups was examined. The chemical structures of the obtained monomers and polymers were confirmed with Fourier transform infrared spectroscopy or ¹H-NMR techniques. The mesomorphic properties and phase behavior of the synthesized monomers and polymers were investigated with polarizing optical microscopy, differential scanning calorimetry, and thermogravimetric analysis (TGA). Copolymers IIP–IVP revealed a smectic-A phase, and VP and VIP revealed a smectic-A phase and a cholesteric phase. The experimental results demonstrated that the glass-transition temperature, the clearing-point temperature, and the mesomorphic temperature range of IIP–VIP increased with an increase in the concentration of mesogenic M_I units. TGA showed that the temperatures at which 5% mass losses occurred were greater than 300°C for all the polymers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2670–2676, 2002