Quasiliving Carbocationic Polymerization. IV. Polymerization of p-tert-Butylstyrene

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Abstract
The mechanism of polymerization of p-tert-butylstyrene (ptBuSt) initiated by the cumyl chloride/BCl3 initiating system in CH2Cl2 at -50°C has been investigated. At and below ∼0.4 M ptBuSt, quasiliving polymerizations proceed, i.e., initiation is instantaneous, termination is absent or reversible, and chain transfer to monomer can be suppressed or eliminated. In the quasiliving range the M n versus [ptBuSt]0 plot is linear and passes through the origin, and a M w/M n decreases much below 2.0 with decreasing [ptBuSt]. GPC traces change from broad multimodal to narrow monomodal and the color of polymerization charges change from colorless to golden-yellow with decreasing [ptBuSt]. The effect of temperature jump subsequent to monomer addition has been examined; however, it does not explain the peculiar monomer concentration effect on the mechanism. Changes in the ionicity may be responsible for this phenomenon.