Stereocontrol in the cationic polymerization of <i>N</i>‐vinylcarbazole

Abstract

Abstract The dependence of the steric microstructure of cationically polymerized poly( N ‐vinylcarbazole) (PVK) upon catalyst, polymerization temperature, and polymerization solvent has been investigated. The effect of polymerization temperature variation was found to be small, whereas the choice of catalyst and polymerization solvent was found to have a strong influence upon the PVK steric microstructure. A correlation was found between the syndiotacticities X s and the π * solvent polarities of the polymerization solvents for a given catalyst. A decrease in X s with increasing π * solvent polarity was observed using BF 3 OEt 2 and AlEt 2 Cl catalysts and has been interpreted in terms of propagation via contact ion‐pair ring structures reversibly formed between the active end group and a preceding repeating unit. The increase in X s with increasing π * solvent polarity observed with several of the catalysts investigated has been interpreted in terms of chain ion pairs whose separation increases with increasing π * solvent polarity. The influence of the various Lewis acid catalysts upon the steric microstructures of cationically polymerized PVK allowed the following order of nucleophilicity to be established: