Synthesis and mesomorphic properties of novel fishbone-like liquid crystalline polysilsesquioxanes VI. Fishbone-like,ester-based liquid crystalline polysilsesquioxanes

Two novel kinds of fishbone-like, ester-based, liquid crystalline, random copolysilsesquioxanes, LC₁-CH₃-P and LC₂-CH₃-P, have been synthesized for the first time by stepwise coupling polymerization (SCP) from trichlorosilane monomers (RSiCl₃) containing mesogenic ester groups, using three main steps including preaminolysis, hydrolysis and polycondensation. Two new monomers 4-(11-trichlorosilylundecloyloxy)phenyl 4-methoxybenzoate (M₁) and 4-(3-trichlorosilylpropoxy)phenyl 4-methoxybenzoate (M₂) have been synthesized by hydrosilylation reaction of trichlorosilane and the mesogens 4-n-undecenoyloxyphenyl 4-methoxybenzoate and 4-allyloxyphenyl 4-methoxy-benzoate, respectively, in the presence of dicyclopentadienylplatinum(II) chloride (Cp₂Ptcl₂) catalyst. The structures and mesomorphic properties of LC₁-CH₃-P and LC₂-CH₃-P were investigated by FTIR, ¹H NMR, ¹³C NMR, ²⁹Si NMR, gel permeation chromatography, polarizing optical microscopy, differential scanning calorimetry and X-ray diffraction. It is proposed from the characterization data that these two polymers not only have an ordered ladder-like, double main chain, but also show thermotropic smectic behaviour with high clearing points and wide mesophase ranges (ΔT), which may hold promise for potential applications as highly stable gas chromatographic stationary phases.