Solution Polymerization of N-vinylcaprolactam in 1,4-dioxane. Kinetic Dependence on Temperature, Monomer, and Initiator Concentrations

The kinetics of the solution free radical po- lymerization of N-vinylcaprolactam, in 1,4-dioxane and under various polymerization conditions was studied. Azobisisobutyronitrile and 3-mercaptopropionic acid were used as initiator and as chain transfer agent (CTA), respec- tively. The influence of monomer and initiator concentra- tions and polymerization temperature on the rate of polymerizations (Rp) was investigated. In general, high conversions were obtained. The order with respect to ini- tiator was consistent with the classical kinetic rate equa- tion, while the order with respect to the monomer was greater than unity. The overall activation energy of 53.6 kJ mol � 1 was obtained in the temperature range 60-80 � C. The decreasing of the absolute molecular weights when increasing the CTA concentration was confirmed by GPC/ SEC/LALS analyses. It was confirmed by UV-visible anal- yses the effect of molecular weights on the lower critical solution temperature of the polymers. It was also verified that the addition of the CTA influenced the kinetic of the polymerizations. V C 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 229-240, 2010