十二烷基苯磺酸钡存在下负离子聚合控制聚苯乙烯立构规整性研究

以正丁基锂(n-BuLi)为引发剂,环已烷为溶剂,通过添加十二烷基苯磺酸钡/四氢呋喃(SDBB/THF),对苯乙烯负离子聚合进行了研究.该体系可在60℃聚合得到立构规整性聚苯乙烯,其丁酮不溶物含量可达80%左右.13C-NMR表征结果显示其微观序列组成以等规结构为主,三元组mm和等规五元组mmmm含量可达57%和45%;DSC谱图中不仅有聚苯乙烯玻璃化温度(100℃),而且在211℃有一熔融峰.GPC结果表明,实测分子量与设计分子量差别较大,且分子量分布较宽。

STEREOSPECIFIC ANIONIC POLYMERIZATION OF STYRENE IN THE PRESENCE OF BARIUM DODECYL BENZENE SULFONATE

The anionic polymerization of styrene has been studied using dodecyl benzene sulfonic acid barium salt(SDBB) /tetrahydrofuran as ligands,n-BuLi as initiator in cyclohexane.The results showed the remarkable effect of SDBB on polymerization.With increasing [SDBB]/[Li],the polymerization rate and monomer conversion decreased,and the gel formed gradually.The polymerization was completely retarded at [SDBB]/[Li]≥ 0.8 at 60℃.The stereospecific polystyrene was obtained at 60℃,and its weight content of methyl ethyl ketone(MEK) insoluble fraction reached about 80%.The 13C-NMR spectra indicated that its microstructure sequence was isotactic-rich polystyrene.The contents of mm triad and mmmm pentad were equal to 57% and 45%,respectively.The Tg of 100℃ and melting temperature at 211℃ were observed in DSC curves.The isotactic content of MEK soluble fraction was also higher than that of PS obtained by conventional anionic polymerization.The GPC results displayed an obvious difference between the theoretical molecular weight and experimental molecular weight.It also indicated a much broader polydispersity of the experimental sample.