New telechelic polymers and sequential copolymers by polyfunctional initiator–transfer agents (inifers). XLI. Kinetic and reactivity studies on sterically hindered inifers

The kinetics of chain transfer to the bifunctional initiating and transfer agents (binifers) 1,4‐di(2‐chloro‐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 −20°C in CH3Cl/n‐hexane and CH2Cl2/n‐hexane mixtures using the m‐tBuDCC/BCl3 binifer system. Chain transfer constants (Ci) to m‐tBuDCC and kt/kp ratios determined in the range from −30°C to −80°C in CH3Cl/n‐hexane mixtures and pure CH3Cl solvent are reported, and the activation energy differences Etr,l − Ep and Et − Ep were calculated. Chain transfer constants to p‐DCC and m‐DMeDCC were determined by the use of pure CH3Cl diluent at −50°C. The chain transfer reactivity of five different inifers is discussed and compared based on CI values obtained under identical conditions, with special regard to the new, sterically hindered binifer m‐DMeDCC of extraordinary reactivity.