A new type of fully aromatic polysilarylenesiloxanes showing high T g was synthesized via the solution polymerization from the bis(diphenylhydroxysilyl)arylene monomers. And the thermal properties of these monomers and polymers were investigated by using differential scanning calorimetry (DSC), and thermogravimetry analysis (TGA). The monomers containing the diphenylsilanol group showed higher melting temperatures and thermal degradation temperatures than those of the monomers containing the dimethylsilanol group. The obtained fully aromatic polysilarylenesiloxanes were insoluble powders, and showed no weight loss in air below 500 C. No glass transition was detected according to the DSC measurements, whereas 3a and 3b showed melting points at 323 and 391 C, respectively. However, 3b held solid-state at melting point. It would be caused by a cross-linking reaction occurring with melting simultaneously. It was found that these were the thermally stable polymer-solids consisted of the organosiloxane polymers.
The in¯uence of the spacer structure on the photochemical phase transition behaviour was explored for azobenzene polymer liquid crystals (azo-PLCs) possessing siloxane spacers in the polymer side chain, and for analogue without the siloxane spacer. The photochemical phase transition of the azo-PLC with the siloxane spacer was found to proceed less e ectively than that of the azo-PLC without the siloxane spacer. It was also con® rmed that the spacer structure does not a ect the trans± cis photoisomerizatio n behaviour of the azobenzene moieties. These results were interpreted in terms of stabilization of the alignment of the mesogens in the liquid crystalline phase by the siloxane spacer, since the siloxane chain is one of the most¯exible spacers and decouples the motion of the polymer backbone from that of the aligned mesogens. Furthermore, the response of the azo-PLCs in the photochemical phase transition was evaluated by means of a laser pulse. The phase transition occurred iñ 300 ms for both samples.
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