MALDI-TOF-MS analysis of living cationic polymerization of vinyl ethers. II. Living nature of growing end and side reactions

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometr y analysis revealed that the HCl-vinyl ether adduct/SnCl4/n-Bu4NCl initiati ng system induced living cationic polymerization of isobutyl vinyl ether in CH2Cl2, at -78 degreesC, that is, the well-resolved spectra demonstrated t hat the produced polymers consist of only one series of polymers carrying o ne initiator fragment at the ru end and one methoxy group originated from q uenching with methanol at the omega end. The polymer molecular weight as we ll as the terminal structure were unchanged even when the reaction mixtures were kept unquenched at -78 degreesC for an interval of more than five tim es longer than the reaction period after complete consumption of monomer, w hich indicates the long lifetime of the living end even under such starved conditions. In contrast, the polymers obtained at a higher temperature, -15 degreesC, showed an additional minor series of polymers formed via proton initiation, originating from adventitious water. Under the starved conditio ns, other side reactions occurred to generate minor series of polymers with an aldehyde omega end or a diisobutyl acetal omega end. Rather surprisingl y, however, unsaturated C=C end groups were not detected, which means the a bsence of beta -proton elimination under these conditions. (C) 2001 John Wi ley & Sons, Inc.