Reverse atom transfer radical polymerization of styrene catalyzed by CuCl₂-2-(8-heptadecenyl)-4,5 dihydro-1H-imidazole-1-ethylamine system

Reverse atom transfer radical polymerization (RATRP) of styrene (St) was investigated at 120 °C with tert-butyl hydroperoxide (TBHP) as initiator, 2-(8-heptadecenyl)-4,5-dihydro-1H-imidazole-1-ethylamine (OLC) as ligand, and FeCl₃, CuCl₂ or NiCl₂ as catalyst. The results indicated that the polymerization was well-controlled and accorded with first order reaction kinetics. The relative molecular mass of the resulted polystyrene increased with St conversion and its relative molecular mass distribution (M_w/M_n) was narrow. For the TBHP-CuCl₂-OLC catalystic system, the polymerization rate was the fastest with high initiation efficiency (f=0.89) and M_w/M_n was the narrowest (1.29). The chain extension reaction revealed that the polymerization was based on RATRP. Apparent rate constant of the polymerization and free radical concentration all increased with rise of temperature. Apparent activation energy and equilibrium enthalpy of the RATRP were 73.39 kJ/mol and 40.88 kJ/mol, respectively.