Structure of side chain liquid crystalline poly(silylenemethylene)s

The structure of side chain liquid crystal of polycarbosilane (-(SiCH₃R-CH₂)n-:R = O(CH₂)₁₁O-Ph-Ph) was studied by X-ray diffraction methods. Four different structures were observed in fiber and powder X-ray diffraction patterns during heating experiments. The room temperature fiber pattern from a sample drawn from isotropic state shows a series of small angle equatorial reflections and a sharp, strong wide angle meridional reflection at 4.4 angstroms, suggesting a S_B phase with layer thickness 30 angstroms and hexagonal packing of the mesogenic side chains perpendicular to the main chain. The asimuthally broad wide angle reflection suggests considerable tilt with respect to the fiber axis.