Living Cationic Polymerization of Vinyl Ether with Methanol/Metal Chloride Initiating Systems: Relationship between Polymerization Behavior and the Nature of Lewis Acids

Abstract

Cationic polymerization of vinyl ether (VE) was examined with methanol/metal chloride initiating systems instead of those with the conventionally used VE−protonic acid adduct initiators. With MoCl5, a highly oxophilic metal halide, the polymerization of isobutyl VE (IBVE) using methanol proceeded in a living fashion in the presence of ethyl acetate, although the reaction was not controlled in conjunction with IBVE−HCl adduct. Furthermore, in the methanol-initiated polymerization, the Lewis acids used could be classified mainly into three categories in terms of polymerization behavior: those producing long-lived species (e.g., MoCl5, NbCl5, and ZrCl4), those inducing uncontrolled polymerization (e.g., GaCl3 and FeCl3), or those showing no activity at all (e.g., ZnCl2 and InCl3). The matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI−TOF−MS) spectra of the product polymers and the direct 1H NMR analysis of the reaction mixtures revealed that the controlled polymerization sta...