Cationic polymerization of N‐vinylcarbazole by triphenylmethyl hexafluoroantimonate

The polymerization of N‐vinylcarbazole (NVC) in methylene dichloride initiated by triphenylmethyl hexafluoroantimonate has been studied at 0 and 20°C. Experiments in an adiabatic calorimeter showed the rates of polymerization to be rapid (t1/2 ∼ 3 sec at [M]0 = 0.050M and [I]0 = 10−6 M), attaining first‐order with respect to monomer concentration after 30–50% conversion. The observed rate constants of propagation decreased with increasing initiator concentration to a constant value after [I]0 ∼ 10−5 M, which was not further reduced by the presence of excess SbF6− anions [from PhCH2(CH3)3NSbF6]. This behavior suggests propagation by both unpaired and paired ions and permits estimates of kp+ = 6 × 105 M−1 sec−1 at 20°C; 4.5 × 105 M−1 sec−1 at 0°C; and kp± = 5 × 104 M−1 sec−1 at both temperatures. Molecular weights (Mn) ranged between 30,000 and 100,000 according to conditions. The degree of polymerization was always < [M]0/[I]0, indicating that transfer reactions govern this chain length. Excess common anion reduced the molecular weights. A stopped‐flow apparatus was employed to monitor initiator consumption and values of ki, estimated at 130 M−1 sec−1 at 20°C and 34 M−1 sec−1 at 0°C.