Poly(methyl methacrylates) with Ruthenium Tris(bipyridine) Cores via NiBr2(PR3)2-Catalyzed Atom Transfer Radical Polymerization (ATRP)

Abstract

Ruthenium(II) tris(bipyridine) complexes derivatized with six α-bromoester functional groups were used as multifunctional initiators for the bulk and solution (toluene) polymerizations of methyl methacrylate (MMA) and methyl acrylate (MA) using NiBr2(PPh3)2 and NiBr2(PBu3)2 as atom transfer radical polymerization (ATRP) catalysts. Both tertiary (1) and secondary (2) halide metalloinitiators were prepared for investigation. The resulting orange-colored polymers were characterized by gel permeation chromatography (GPC) in chloroform. The molecular weight distributions of the poly(methyl methacrylates) (PMMAs) were narrow (toluene, Mw/Mn = 1.1−1.3; bulk, Mw/Mn < ∼1.3 at <50% conversion). The presence of [Ru(bpy)3]2+ in the eluting polymers was verified by in-line, diode-array UV/vis spectroscopic analysis. For polymerizations of MMA in toluene at 80 °C using the tertiary initiator and NiBr2(PPh3)2 as the catalyst, Mn vs percent conversion and pseudo first-order kinetics plots were linear. Thus, these conditi...