THE PROPAGATING SPECIES IN LIVING CATIONIC POLYMERIZATION - LIVING NATURE AND STERIC STRUCTURE OF POLYMERS

This paper discusses the nature of the living growing. species in cati onic polymerization from the viewpoint of the steric structure of poly (isobutyl vinyl ether) [poly(IBVE)]. At -78 degrees C, living polymeri zation was induced: with the HCl-IBVE adduct (1)/ZnCl2 system in a EtN O2/CH2Cl2 mixture, whereas similar systems with EtAlCl2 led to convent ional cationic polymerization. In this polar medium, both systems gave polymers with very similar and low isotacticity (meso approximate to 56%), indicating that the propagating reaction is mediated by free ion s. Thus, regardless of solvent polarity, or involvement of free ions o r ion pairs, living cationic polymerization requires a suitably nucleo philic counteranion. As model reactions of the growing species, 1/ZnCl 2 and 1/EtAlCl2 were directly analyzed by H-1 NMR spectroscopy.