NEW TELECHELIC POLYMERS AND SEQUENTIAL COPOLYMERS BY POLYFUNCTIONAL INITIATOR-TRANSFER AGENTS (INIFERS) .41. KINETIC AND REACTIVITY STUDIES ON STERICALLY HINDERED INIFERS

In the reported experiments, the kinetics of chain transfer to the bifunctional initiating and transfer agents (binifers) 1,4-di(2-dichloro-2-propyl)benzene (p-DCC), 1,3-di(2-chloro-2-propyl)-5-tert-butylbenzene (m-tBuDCC), and 1,3-di(2-chloro-2-propyl)-4,6-dimethylbenzene (m-DMeDCC) in the polymerization of isobutylene has been investigated. Chain transfer to monomer was shown to be absent up to minus 20 degree C in CH//3Cl/n-hexane and CH//2Cl//2/n-hexane mixtures using the m-tBuDCC/BCl//3 binifer system. Chain transfer constants (C//1) to m-tBuDCC and k//t/k//p ratios determined in the range from minus 30 degree C to minus 80 degree C in CH//3Cl/n-hexane mixtures and pure CH//3Cl solvent are reported, and the activation energy differences E//t//r//,//I minus E//p and E//t minus E//p were calculated. Chain transfer constants to p-DCC and m-DMeDCC were determined by the use of pure CH//3Cl diluent at minus 50 degree C. The chain transfer reactivity of five different inifers is discussed and compared based on C//1 values obtained under identical conditions, with special regard to the new, sterically hindered binifer m-DMeDCC of extraordinary reactivity.