Determination of the relative rates of addition of styrene and acrylonitrile to the 1-(1,3-diphenyl)propyl and 1-(3-cyano-1-phenyl)propyl radicals. Evidence for a penultimate effect in radical copolymerization
作者:Douglas A. Cywar、David A. Tirrell
DOI:10.1021/ja00201a041
日期:1989.9
1b as initiator allows accurate determination of the relative rates of addition of these monomers (k_s/k_A) to the 1-( 1,3-diphenylpropyl) radical (2b); similarly, analysis of SAN copolymers prepared with IC allows determination of k_s/k_A for the 1-(3-cyano-l-phenylpropyl) radical (2c). Significantly different preferences of the radicals for addition of styrene and acrylonitrile were observed; we obtain
1,1'-偶氮二(1,3-[1-^(13)C]二苯基丙烷)(1b)和4,4'-偶氮二(4-苯基[4-^(13)C]丁腈)(1C)分别以 10% 和 1.2% 的总产率制备,两者均以 Ba^(13)CO_3(99 原子%)为原料。分析以 1b 作为引发剂制备的苯乙烯-丙烯腈 (SAN) 共聚物的端基浓度,可以准确测定这些单体 (k_s/k_A) 与 1-(1,3-二苯丙基) 自由基 (2b) 的相对加成速率); 类似地,分析用 IC 制备的 SAN 共聚物可以确定 1-(3-氰基-1-苯基丙基) 自由基 (2c) 的 k_s/k_A。观察到自由基对苯乙烯和丙烯腈加成的明显不同偏好;我们得到 2b 的 k_s/k_A = 0.21 f±0.01 和 2c 的 k_s/k_A = 0.52 ± 0.03。这些结果表明 1-(1-苯基烷基) 自由基的 k_s/k_A 对自由基中心的取代 y 敏感,并为