丁基锂引发苯乙烯-异戊二烯-苯乙烯三嵌段共聚物合成及其结构与性能表征

Synthesis and Characterization of Triblock Copolymers Polystyrene-Polyisoprene-Polystyrene Initiated by Butyl Lithium

分别以正丁基锂与叔丁基锂为引发剂,利用活性阴离子聚合并采用分步加料方法制备了高转化率的聚苯乙烯-异戊二烯-苯乙烯三嵌段共聚物(SIS)。采用FT-IR、1 H-NMR对产物的精细结构进行了表征,证实其结构与设计相一致。DSC研究结果显示产物存在3个玻璃化转变温度(Tg),是典型的微相分离共聚物。聚合工艺研究显示:升高聚合温度及添加引发促进剂均可明显提高反应速率,第一段引发时叔丁基锂的引发效率较正丁基锂高,但两者在第二段与第三段无明显区别。将SIS成型后,研究了分子量及嵌段比对弹性体力学性能的影响。结果显示:随分子量的增大拉伸强度及断裂伸长率均逐步增大,随聚苯乙烯链段含量的增大拉伸强度先增大后减小,断裂伸长率逐步减小。

A triblock eopolymer polystyrene-polyisoprene-polystyrene （SIS） with high conversion rate was synthesized by anionic polymerization using step feeding method, n-butyl lithium and t-butyl lithium as initiator. The chemical structure of the product was characterized by FT-IR and 1 H-NMR, which was confirmed consistence with the design. The result of DSC revealed that the product was typical micro-phase separation copolymers presenting with three glass transition temperatures. The study of polymerization process indicated that increasing temperature and adding accelerator could obviously increase the reaction rate. The initiation efficiency of t-butyl lithium was higher than that of n-butyl lithium when the first block was initiated, but no significant difference was observed in the poly- merization of second and third blocks. The influence of molecular weight and block ratio on mechanical properties of the elastomer was studied after heat curing and molding of SIS. The result indicated that the tensile strength and elongation at break gradually increased along with the increasing of molecular weight, and with the increasing of polysty- rene chain segment content, the tensile strength increased at first and then declined, while the elongation at break decreased gradually.