2-[(diphenylphosphino)methyl]pyridine as ligand for iron-based atom transfer radical polymerization

2-[(Diphenylphosphino)methyl]pyridine (DPPMP) was successfully used as a bidentate ligand in the iron-mediated atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) with various initiators and solvents. The effect of the catalytic system on ATRP was studied systematically. Most of the polymerizations with DPPMP ligand were well controlled with a linear increase in the number-average molecular weights (M-n) versus conversion and relatively low molecular weight distributions (M-w/M-n = 1.10-1.3) being observed throughout the reactions, and the measured molecular weights matched the predicted values. Initially added iron(III) bromide improved the controllability of the polymerization reactions in terms of molecular weight control. The ratio of ligand to metal influenced the controllability of ATRP system, and the optimum ratio was found to be 2:1. It was shown that ATRP of MMA with FeX2/DPPMP catalytic system (X = Cl, Br) initiated by 2-bromopropionitrile (BPN) was controlled more effectively in toluene than in polar solvents. The rate of polymerization increased with increasing the polymerization temperature and the apparent activation energy was calculated to be 56.7 KJ mol(-1). In addition, reverse ATRP of MMA was able to be successfully carried out using AIBN in toluene at 80 degrees C. Polymerization of styrene (St) was found to be controlled well by using the PEBr/FeBr2/DPPMP system in DMF at 110 degrees C. (C) 2008 Wiley Periodicals, Inc.