乙烯基取代聚苯撑硅氧烷的热性质

Thermal Property of Vinyl Substituted Poly(Silphenylene Siloxane)s

以1,4-双(二甲基硅基)苯、二甲基二甲氧基硅烷和甲基乙烯基二甲氧基硅烷为原料,用Si-H/Si-OR缩聚的方法制备了一系列聚(四甲基对硅亚苯基-二甲基-甲基乙烯基)硅氧烷三元共聚物(PTMPS/DMS/VMS),并用TG与DSC对共聚物的热性质进行了表征。结果表明,乙烯基能显著提高PTMPS/DMS/VMS在氮气中的热稳定性,且当DMS/VMS为50:50(摩尔比)时热稳定性最好。在空气中,引入乙烯基同样能提高PTMPS/DMS/VMS的热稳定性,但其影响比氮气中小得多。PTMPS/DMS/VMS的T_g与VMS链节含量的关系为:T_g=-56.1-0.04[VMS%],T_g随共聚物中VMS链节含量的增加而线性降低,但降低的幅度很小(不超过4.3℃)。

Poly（tetramethyl-p-silylphenylene-dimethyl-vinylmethyl siloxane）s（PTMPS/DMS/VMS） are synthesized by Si-H/Si-OR polycondensation process using 1,4-bis （dimethylsilyl） benzene, dimethyldimethoxylsilane and vinylmethyldimethoxylsilane as start materials. The thermal properties of PTMPS/DMS/VMS copolymers are charac- terized by TG and DSC. The results shows that vinyl groups greatly enhance the thermal stability of the PTMPS/DMS/ VMS copolymers in nitrogen, and the polymers with 50% DMS and 50%VMS units possess the highest thermal stability. Vinyl groups also enhance the thermo-oxidative stability of the PTMPS/DMS/VMS copolymers in air, but it is less prominent than in nitrogen. The relationship of the Tg and the proportions of VMS units can be demonstrated as Tg =-56. 1- 0. 04 [VMS% ]. The Tg of the PTMPS/DMS/VMS copolymers decrease linearly with the increase of the proportion of VMS units,but the extent is much low,no more than 4. 3℃.