Detailed studies on the peroxidisulfate (PDS) initiated graft copolymerization of N-methyl aniline (NMA) with poly(ethylene terepthalate) (PET) were carried out in p-tolene sulfonic acid medium under nitrogen atmosphere. Experiments were designed to follow the rate of formation R-h of the poly(N-methyl aniline (PNMA), simultaneously with the rate of grafting of PNMA onto PET. Effects of concentration of NMA, PDS, PET, time, and temperature on R-h and graft parameters were followed. Kinetic equations were deduced to correlate the changes in the rate withexperimental conditions. Graft copolymers were isolated and grafting of PNMA onto PET was confirmed through FTIR, thermogravimetric analysis, and conductivity measurements. Tensile measurements showed that grafting of PNMA did not alter the tensile properties of PET. (C) 2004 Wiley Periodicals, Inc.