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 spectrometry analysis revealed that the HCl-vinyl ether adduct/SnCl4/n-Bu4NCl initiating system induced living cationic polymerization of isobutyl vinyl ether in CH2Cl2, at -78 degreesC, that is, the well-resolved spectra demonstrated that the produced polymers consist of only one series of polymers carrying one initiator fragment at the ru end and one methoxy group originated from quenching with methanol at the omega end. The polymer molecular weight as well as the terminal structure were unchanged even when the reaction mixtures were kept unquenched at -78 degreesC for an interval of more than five times longer than the reaction period after complete consumption of monomer, which 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 conditions, other side reactions occurred to generate minor series of polymers with an aldehyde omega end or a diisobutyl acetal omega end. Rather surprisingly, however, unsaturated C=C end groups were not detected, which means the absence of beta -proton elimination under these conditions. (C) 2001 John Wiley & Sons, Inc.