Living Carbocationic Polymerization. Xxxvii. Asymmetric Telechelic Polyisobutylenes by Lactone/Bcl3 Initiating Complexes

A new family of initiating systems of carbocationic polymerization has been introduced comprising complexes of a lactone and a Lewis acid. It has been shown by model experiments that the true initiating species are the lactone/Lewis acid complexes. A series of these complexes has been investigated in scouting experiments of isobutylene polymerization to identify an initiating complex which facilitates the diagnosis of living polymerizations. The γ-tolyl-γ-valerolactone/BCl 3 complex has been found to yield high initiation efficiencies at low isobutylene conversions and therefore has been selected for detailed investigation. It has been demonstrated that this lactone in the presence of BCl 3 effects the living polymerization of isobutylene. A variety of lactone/BCl 3 complexes has been found to be efficient initiators for the polymerization of styrene, 4-methyl-styrene, and 2,4,6-trimethylstyrene; however, under the conditions employed, these polymerizations were not living. The mode of forced termination by the addition of different quenching agents has been studied in model experiments using ester/Lewis acid complexes as model compounds. Forced termination has been found to result in a tertiary chlorine end group in model experiments as well as in functionalization experiments by adding the quenching agent at the end of the polymerization. Living polymerizations initiated by lactone/BCl 3 complexes have been shown to yield α,ω-asymmetric telechelic polyisobutylenes; that is, PIBs capped with an ester or acid group at the α-terminus and a tertiary chlorine at the ω-terminus. End-group characterizations have shown theoretical functionalities within experimental variations.