Poly(acrylic acid) was grafted onto methylcellulose in aqueous media by a potassium permanganatep-xylene redox pair. Within the concentration range from 0.93 x 10(-3) to 9.33 X 10(-3) M, p-xylene, the graft copolymerization reaction exhibited minimum and maximum graft yields and was associated with two precursor-initiating species, a p-xylyl radical and its diradical derivative. The efficiency of the graft was low, not higher than 12.9% at a p-xylene concentration of 0.93 X 10(-3) M and suggested the dominance of a competitive homopolymerization reaction under homogeneous conditions. The effect of permanganate on the graft yield was normal and optimal at 135% graft yield, corresponding to a concentration of the latter of 33.3 X 10(-3) M over the range from 8.3 X 10(-3) to 66.7 X 10(-3) M. The conversion in graft yield showed a negative dependence on temperature in the range 30-60degreesC and suggested a preponderance of high activation energy transfer reaction processes. The calculated composite activation energy for the graft copolymerization was 7.6 kcal/mol. (C) 2003 Wiley Periodicals, Inc.