n-BuLi/DME引发的α-甲基苯乙烯阴离子平衡聚合动力学及反应机理的研究

KINETIC STUDIES ON ANIONIC EQUILIBRIUM POLYMERIZATION OF α-METHYLSTYRENE INITIATED BY n-BuLi/DME SYSTEM

研究了以n-BuLi为引发剂、环己烷为溶剂,2,5-二氧己烷(DME)为添加剂,在20℃下进行α-甲基苯乙烯(α-MeSt)的阴离子平衡聚合反应。测定了聚合(解聚)速率常数与添加剂浓度的关系。提出了[DME]/[BuLi](mol比)小于1.66、大于33.3及介于两者之间时的平衡聚合动力学方程。比较了以四氢呋喃,DME及2,5,8-三氧壬烷为添加剂时,α-MeSt的阴离子平衡聚合反应的规律及特征。

The kinetics and mechanism of anionic equilibrium polymerization of α-methylstyrene in cyclohexane, with n-butyllithium (n-BuLi) as initiator and 2 , 5 -dioxahexane ( DME ) as polar additive were investigated. The constants of apparent propagation rate ka, or of depropagation rate kad were evaluated over a wide concentration range of DME. The kinetics equation of equilibrium polymerization at molar ratio [DME]/ [BuLi] < 1.66, [DME]/ [BuLi] >3.3 and 1.66 < [DME] / [BuLi] < 33.3 were established. The monomer equilibrium concentrations, [M]., at above mentioned ratios which could be used to control the degree of polymerization were obtained. The reaction features of anionic polymerization of α-methylstyrene adopting various polar additives were compared.