Cationic and free radical propagation of copolymerization by the N-vinyl carbazole cation-radical

Abstract

Copolymerization of N-vinyl carbazole (NVC) and p-methoxy styrene in ethylene dichloride (EtCl2) at 25°C gives copolymers of virtually identical composition whether the reaction is initiated by the cationic reagent BF3OEt2 or by the typical electron-acceptor tetracyanoethylene (TCNE), provided the latter system is shielded from daylight. The propagation mechanism is concluded to be cationic in both cases. The derived reactivity ratios are: r1(NCV)=21·4±0·81;r2=0·13±0·005(BF3OEt2)r1=20·1±1·5;r3=0·09±0·01(TCNE)A photochemically induced copolymerization is found in daylight with TCNEĒtCl2 and with EtCl2 alone giving copolymers slightly richer in p-MeO styrene. Evidence is offered that under these conditions, both cationic and a parallel free radical propagation mechanism can proceed. The reactivity ratios for the cationic copolymerization by BF3OEt2 show virtually no change over the temperature range 25° to 0°C.