An investigation of free-radical copolymerization propagation kinetics of styrene and 2-hydroxyethyl methacrylate

Free-radical copolymerization propagation kinetics of styrene (ST) and 2- hydroxyethyl methacrylate (HEMA) have been investigated using pulsed laser polymerization (PLP) combined with size exclusion chromatography (SEC) and proton NMR. Monomer reactivity ratios for bulk ST/HEMA copolymerization are rHEMA = 0.49 and rST = 0.27, with no significant variation with temperature found between 50 and 120 C. The composition-averaged copolymerization propagation rate coefficient, kp,cop, is well represented by the implicit penultimate unit effect (IPUE) model. The copolymerization kinetics of HEMA with ST is quite similar to that of glycidyl methacrylate (GMA) with ST. A computational study based on quantum chemistry supports the finding that GMA and HEMA are more reactive toward ST radicals compared to alkyl methacrylates.