Thermally-sensitive and Biocompatible Poly(N-vinylcaprolactam): A Kinetic Study of Free Radical Polymerization in Ethanol

Abstract

Using nuclear magnetic resonance (1H-NMR), a kinetic study on the polymerization of N-vinylcaprolactam (NVCL) was performed under different polymerization conditions. The homopolymers were synthesized by free radical polymerization in ethanol, and azobisisobutyronitrile (AIBN) and 3-mercaptopropionic acid were used as the initiator and chain transfer agent (CTA), respectively. Moreover, the effect of the monomer concentration, initiator concentration and polymerization temperature on the kinetics of the reaction was evaluated. The results revealed that the aforementioned parameters had a significant effect on the polymerization rate (Rp ): as the monomer and initiator concentration increased, an increase in Rp and the overall activation energy was observed. Poly(N-vinylcaprolactam) (PNVCL) is a thermoresponsive and biocompatible polymer that possesses a LCST (low critical solution temperature) near physiological temperature. Thermoresponsive polymers with low molar masses are useful for biomedical applications; thus, the effect of the molar mass on the polymerization rate and the LCST of PNVCL was studied. The number-average molar mass () and the polydispersity of the homopolymers were measured with a gel permeation chromatograph coupled to a triple detector (GPC/SEC/LALS), and the LCST of the PNVCL was determined by UV-visible analyses.