New telechelic polymers and sequential copolymers by polyfunctional initiator‐transfer agents (inifers). II. Synthesis and characterization of α,ω‐di(tert‐chloro)polyisobutylenes

Detailed understanding of the mechanism of initiation and chain transfer in BCl3‐coinitiated isobutylene polymerization led to the efficient synthesis of symmetric telechelic polyisobutylenes carrying ∼CH2C(CH3)2Cl groups at either end of the molecule Cl‐PIB‐Cl. The synthesis is based on the use of inifers, i.e., bifunctional initiator‐transfer agents that effect controlled initiation and propagation in the absence of chain transfer to a monomer. Specifically, the synthesis of Cl‐PIB‐Cl was achieved by the p‐dicumyl chloride/BCl3/isobutylene/CH2Cl2 system. According to the inifer mechanism each Cl‐PIB‐Cl contains two terminal tertiary chlorines and one phenyl group at the interior of the chains. The structure of this new symmetric telechelic polymer has been established by detailed characterization studies including a sensitive new gel permeation chromatography (UV plus RI) analysis method, 1H‐NMR, kinetic experiments, and chemical derivatization. The Cl‐PIB‐Cl molecule is a key intermediate for the synthesis of hosts of new materials, e.g., triblock copolymers, α,ω‐diolefins, and α,ω‐difunctional polymers.