QUANTUM-CHEMICAL STUDY OF THE MECHANISM OF THE LIVING CATIONIC POLYMERIZATION BY ESTER-BORON TRIHALIDE INITIATORS

Semiempirical MNDO calculations of model systems simulating cationic i nitiating systems of the BCl3/ester type have been carried out. Intera ctions between BX(3) (X = F, Cl) and methyl acetate (MA) have been com pared. Properties of six-membered cyclic transition states for the rea ction between MA and propylene in the presence of BCl3, previously pro posed as a mechanism of living cationic polymerization, have been inve stigated. An alternative mechanism of polymerization via zwitterionic complexes formed between BCl3 and monomer has been suggested. The cati onic center of this zwitterionic complex has been found to be stabiliz ed by the ester component of the initiating system.