Quasiliving Carbocationic Polymerization. VI. Quasiliving Polymerization of lsobutyl Vinyl Ether

Quasiliving carbocationic polymerization of isobutyl vinyl ether (IBVE) was achieved with the p-dicumyl chloride (p-DCC)/AgSbF6 initiating system in methylene chloride solvent at -70 and -90°C. The monomer was introduced as a steady, continuous stream to a premixed, well-stirred initiator solution (quasiliving technique). The number-average molecular weights (M n) of poly(IBVE) increased linearly with thecumulative weight of added monomer (WIBVE), and linear M n versus WIBVE plots passing through the origin were obtained. M n's were inversely proportional to the initial initiator concentration ([p-DCC]0) and were in agreement with theoretical values (WIBVE/[p-DCC]0) expected for quasiliving systems, The number of polymer chains produced per unit initiator (p-DCC) was close to unity and remainec unchanged during the early stages of the reactions. The poly-(IBVE) exhibited narrow molecular weight distributions with M w/M n ranging from 1.4 to 1.7. Polymerizations using methylene chloride solvent at highertemperatures (-30 and -50°C) also yielded linear ascending M n versus WIBVE plots; however, they showed intercepts. Using a nonpolar solvent (n-heptane), M n did not increase with WIBVE (-50°C) or M n versus WIBVE plots were strongly curved (-70°C), indicating slow initiation and the absence of quasiliving conditions. Evidently optimum conditions for quasiliving IBVE polymerization prevail only in polar media at lower temperatures.