Depelopment of supported catalysts for living polymerization of olefins and its application to gas-phse polymerization

因此，活性聚合引起了人们的广泛关注，已有多篇论文报道了均相催化体系下丙烯的活性聚合。然而，用负载式单位点催化体系进行丙烯活性聚合的例子很少，这从实际的角度来看应该是非常重要的。我们以前发现，用三烷基铝修饰的甲基铝氧烷（dMMAO）激活的螯合（二胺）二甲基钛配合物(1)在0℃下在庚烷中进行丙烯的活性聚合。以硅胶、氧化铝和氧化镁为原料，通过载体与dMMAO在庚烷中反应制备负载型dMMAO，并与1进行丙烯聚合，以阐明干燥后的MMAO的负载作用。无论金属氧化物如何，负载体系都能在0℃下对干燥的MMAO进行丙烯活性聚合，无需任何诱导期。这些体系的传播速率常数（k_p）和聚合物的分子量分布（M_w/M_n）取决于所采用的金属氧化物。k_p值随着载体上MMAO的Lewis酸度的增大而增大，增大的M_w/M_n是由载体的非均质性引起的Lewis酸度分布所致。该系统得到无规聚丙烯，而不考虑金属氧化物的干燥MMAO。我们还用ansa-fluorenylamidodimethyltitanium(2)进行了丙烯聚合，当被dMMAO激活时，它可以代替1进行丙烯的活性聚合。虽然硅胶和氧化铝的2负载dMMAO体系显示出很高的初始活性，但体系失活并发生链转移。结果表明，配合物与负载型活化剂的结合对负载型催化体系的活性聚合具有重要意义。

The living polymerization, therefore, has attracted much attention and several papers have reported on the living polymerization of propene by homogeneous catalytic systems. There are, however, few examples for living polymerization of propene by supported single-site catalytic systems, which should be very important from the practical point of view. We have previously found that living polymerization of propene proceeded in heptane at 0℃ by a chelating (diamide) dimethyltitaniumcomplex (1) activated with trialkylaluminum-free modified methylaluminoxane (dMMAO), which is easily soluble in hydrocarbons.We prepared supported dMMAOs using silica gel, alumina and magnesia by the reaction of the support and dMMAO in heptane and conducted propene polymerization with 1 to clarify the supporting effects of dried MMAO. The supported systems conducted living polymerization of propene at 0℃ without any induction period regardless of the metal oxides for dried MMAO. The propagation rate constants (k_p) of these systems and the molecular weight distribution (M_w/M_n) of the produced polymer depended on the metal oxide employed. The k_p value increased with the increase in Lewis acidity of MMAO on the support and the broadening (M_w/M_n) was ascribed to the distribution of Lewis acidity caused by the heterogeneity of the supported cocatalyst. The systems gave atactic polypropylene regardless of the metal oxides for dried MMAO.We also conducted propene polymerization with ansa-fluorenylamidodimethyltitanium (2), which conducts living polymerization of propene when activated with dMMAO, in place of 1. Although the 2-supported dMMAO systems of silica-gel and alumina showed very high initial activity, the system deactivated and chain transfer also occurred. The results indicated that the combination of the complex and the supported activator was very important for the living polymerization with supported catalytic systems.