The controllability of the atom transfer radical polymerization of methyl methacrylate in the polar solvent N,N-dimethylformamide and the nonpolar solvent xylene with 4-(chloromethyl)phenyltrimethoxysilane as an initiator and with CuCl/2,2'-bipyridine and CuCl/4,4'-di(5-nonyl)-2,2'-bipyridine as catalyst systems was studied. Gel permeation chromatography analysis established that in the nonpolar solvent xylene, much better control of the molecular weight and polydispersity of poly(methyl methacrylate) was achieved with the CuCl/4,4'-di(5-nonyl)-2,2'-bipyridine catalyst system than with the CuCl/2,2'-bipyridine as catalyst system. In the polar solvent N,N-dimethylformamide, unlike in xylene, the polymerization was more controllable with the CuCl/2,2-bipyridine catalyst system than with the CuCl/4,4'-di(5-nonyl)-2,2'-bipyridine catalyst system. (c) 2007 Wiley Periodicals, Inc.