Propagation Rate of the Cationic Polymerization of 2,4,6-Trimethylstyrene: A Linear Free Energy Approach
作者:Herbert Mayr、Armin R. Ofial、Holger Schimmel
DOI:10.1021/ma048389o
日期:2005.1.1
are considerably lower than that of the styryl cation (E = 9.6). As a consequence, the propagation rate constant of the cationic polymerization of 2,4,6-trimethylstyrene is considerably lower than that of styrene. Substituting these values into the correlation log k20 °C = s(N + E) yields a propagation rate constant of 3 × 107 M-1 s-1, which has to be considered an upper limit because extra steric strain
已经进行了苯甲基阳离子与2,4,6-三甲基苯乙烯的反应动力学以确定其亲核参数N = 0.68和s = 1.09,这与苯乙烯相当,并且亲核参数比4-甲基苯乙烯少,表明该化合物的阻滞作用邻甲基。动力学研究2,4,6-三甲基苯乙烯基阳离子6 +和相应的二聚体7 +与参考亲核试剂2-氯丙烯的反应,使我们能够计算出非常相似的亲电参数E(6 +)= 6.04和E(7 +)= 6.16,其远低于苯乙烯基阳离子的阳离子(E= 9.6)。结果,2,4,6-三甲基苯乙烯的阳离子聚合的传播速率常数大大低于苯乙烯。将这些值代入相关对数k 20 ° C = s(N + E)时,得出的传播速率常数为3×10 7 M -1 s -1,必须将其视为上限,因为在此过程中会产生额外的空间应变。这种相关性不包括7 +与2,4,6-三甲基苯乙烯的反应。