稀土配位催化异戊二烯、丁二烯、苯乙烯选择性三元共聚合制备集成橡胶

China ranks No.1 of the world contineously in the past seven years for consuming rubbers, meanwhile the pressures of the resource shortage and environment polution increase daily, which make the synthesis of green tires of low rolling resistance, sllipery resistance, and anti-erasion become urgent. No single rubber can satisfy all these properties simultaneously. The terpolymer of isoprene, butadiene and styrene, namely, the integral rubber, combines the flexible polybutadiene and anti-aging polyisoprene and rigid polystyrene into one polymer chain, seemingly to be the ideal green ruber. To date, copolymerization of these three monomers is initiated only by the anionic catalyst, however, the composition and monomer sequence distribution as well as the cis-1,4 regularity of the polydiene blocks are difficult to control, which has been a tough project in this research area. Coordination polymerization has privilages of regio- and stereo-regularity control. Thus, in this project, we intend to construct novel catalytic systems via designing ligands that specifically and electronically matching the Lewis acid and ionic size of lanthanide metals, and to establish living-chain-transfer systems through rapid and reversible interaction of the selected main-group activators and the catalysts active for the polymerization of conjugated dienes and styrene, respectively, to realize the random copolymerization of theses three monomers; and synthesize new integral rubber in which the conjugated diene repeated units are highly cis-1,4 regulated and the styrene units are atactic, and the composition and its distribution, the molecular weight and molecular weight distribution are well controlled; the relationship among the structural factors, the catalytic performance as well as polymer properties will be elucidated.

我国橡胶消耗量连续七年排世界第一，而资源与环境压力与日俱增，生产抗湿滑、低滚动阻力、耐磨的绿色轮胎势在必行。单一胶种不能同时满足这些要求。丁二烯-异戊二烯-苯乙烯三元无规共聚物即集成橡胶，将聚丁二烯的柔顺性、聚异戊二烯的耐老化性和聚苯乙烯的刚性结合到一条大分子链，有望成为理想的绿色轮胎胶料。目前只有阴离子催化剂能引发这三种单体共聚，但有效调控共聚物的组成及分布、提高双烯烃链段的顺式含量是该领域的难题。配位聚合的优势在于区域与立体选择性。本课题将设计空间、电子效应不同的配体通过与中心金属Lewis酸性和离子半径的匹配获得新型催化体系，或通过筛选主族金属烷基化试剂分别与双烯烃和苯乙烯聚合催化剂进行可逆、快速交换反应构筑活性链转移体系，实现这三种单体配位共聚合，制备双烯烃高顺1,4-结构而苯乙烯无规结构、组成及分布、分子量及其分布可控的新型集成橡胶；揭示配体-催化剂性能-共聚物性能的关系。

本课题通过新型稀土催化剂的设计，首先实现了异戊二烯的高3,4-、高全同3,4-、高间同3,4-选择性聚合，得到3,4-聚异戊二烯---新概念集成橡胶的重要组分；以及在3,4-活性异戊二烯聚合基础上制备出聚3,4-异戊二烯与极性单体的嵌段共聚物、功能化聚双烯烃橡胶。通过两种稀土催化剂对同一种异戊二烯单体不同选择性选择性、活性链转移配位聚合，以及一种催化剂对丁二烯和异戊二烯不同选择性、活性链转移配位聚合，实现了主链含有低滚阻和耐磨性能的顺式1,4-聚双烯烃链段和抗湿滑、低滚阻的3,4-聚异戊二烯链段的新概念集成橡胶。通过侧臂空间和给电子效应，首次发现催化剂不被极性单体毒化反而活化的机理，实现极性、功能化苯乙烯衍生物的高全同、间规聚合，及其与非极性苯乙烯序列可控共聚合，为未来通过配位聚合法合成功能化溶聚丁苯橡胶提供理论基础及可能。