Preparation of high-molecular-weight poly(N-vinylcarbazole) by the photoinduced low-temperature solution polymerization of N-vinylcarbazole in 1,1,2,2-tetrachloroethane

For the preparation of high-molecular-weight (HMW) poly(N-vinylcarbazole) (PVCZ) with a narrow molecular weight distribution, N-vinylcarbazole (VCZ) was solution-polymerized in 1,1,2,2-tetrachloroethane (TCE) at -20, 0, and 20°C with photoinitiation. The effects of the polymerization temperature and the concentrations of the polymerization solvent and photoinitiator on the polymerization behavior and molecular parameters of PVCZ were investigated. A low polymerization temperature with photoirradiation was successful in obtaining HMW PVCZ with a smaller temperature rise during polymerization than that for thermal free-radical polymerization by azobisisobutyronitrile (AIBN). The photo-solution-polymerization rate of VCZ in TCE was proportional to [AIBN]^0.45. The molecular weight was higher and the molecular weight distribution was narrower for PVCZ made at lower temperatures. For PVCZ prepared in TCE at -20°C with a photoinitiator concentration of 0.00003 mol/mol of VCZ, a weight-average molecular weight of 920,000 was obtained, with a polydispersity index of 1.46, and the degree of transparency converged to about 99%.