Anionic polymerization and copolymerization of isoprene and styrene with butyllithium in the presence of tetraethyltin

Abstract

A characteristic feature of polymerization catalysed by lithium alkys is the dependence of the kinetics of the process, the structure of polydiene polymers and the composition of copolymers on the nature of the polymerization medium. In hydrocarbons a coordination type of process occurs, in which the counter-ion has a considerable effect on the propagation step [1, 2]. In electron-donor solvents the mechanism of the process is altered by solvation of the active centres. The rate of polymerization is higher in these solvents and the composition and structure of copolymers are altered [3]. There has been little study of the effect of electron-accepting compounds on polymerization with RLi. It was found in a study by Welch and his collaborators [4] of the polymerization of styrene, catalysed by n-C 4H 9Li, that Lewis acids, tri-isobutylaluminium and di-n-butylzinc act as inhibitors. The authors suggest that aluminium and zinc alkyls, which are acceptors in relation to n-C 4H 9Li, form complexes with the latter that are inactive in polymerization. The possibility of formation of such complexes has been investigated by Wittig[5] and more recently by Waak[6].