Free radical grafting of some hydrophilic monomers onto unsaturated segmented polyurethanes — a kinetic study

Grafting of unsaturated segmented polyurethanes with some hydrophilic monomers such as N‐vinyl pyrrolidone, 2‐hydroxyethylmethacrylate and acrylamide in N,N‐dimethylformamide have been studied using 2,2′‐azobisisobutyronitrile (AIBN) as initiator. Graft copolymers were isolated from homopolymers by selected solvent extraction using a Soxhlet apparatus. A kinetic study of graft copolymerization reactions showed that the reactions follow the conventional kinetic behaviour of free radical polymerization. The dependencies of the grafting rate on initiator and N‐vinyl pyrrolidone concentrations were of 0.5 and 1.00 order, respectively. However, for the 2‐hydroxyethylmethacrylate, the dependencies of the grafting rate on initiator and monomer concentrations were found to be of 0.5 and 2.00 order, respectively. The overall activation energy for the graft copolymerization of the 2‐hydroxyethylmethacrylate and N‐vinyl pyrrolidone were 21.81 kJ/mol and 16.28 kJ/mol, respectively.