Grafting of Poly(N-Vinylcaprolactam) in polyurethane by gamma radiation

Poly (N-vinylcaprolactam) (PNVCL) is a thermoresponsive, biocompatible, non-toxic polymer with a phase transition temperature from hydrophilic to hydrophobic state (Tpt) close to the physiological one. This temperature is influenced by PNVCL molar mass and its copolymerization. In this work, gamma radiation at doses of 5 and 20 kGy was used to graft PNVCL chains onto films of thermoplastic polyurethane (TPU). PNVCL homopolymers were also developed by gamma radiation at the same conditions. The materials were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), viscometry and thermogravimetric analaysis (TGA). PNVCL grafting enabled thermoresponsive character to TPU films, as observed by changes in water-surface contact angles above and below Tpt. The Tpt of the developed homopolymers determined by cloud point and rheological analysis was close to 30 degrees C. These results demonstrated the feasibility of developing a graft copolymer with thermoresponsive properties, with the innovation of grafting PNVCL onto TPU films using gamma radiation.