The radical copolymerization of styrene with methacrylic acid (MAA) initiated by triphenylbismuthonium 1,2,3,4-tetraphenylcyclopentadienylide in dioxan at 80 +/- 0.1 degrees C for 3 h results in the formation of alternating copolymer as evidenced from the values of reactivity ratios as r(1) (styrene) = 0.03 and r(2) (MAA) = 0.025. The kinetic expression is R-p alpha [1](0.5) [Sty] [MAA] and overall energy of activation is computed to be 23 kJ/mol. The FTIR spectrum of the copolymer shows the presence of bands at 3054 cm(-1) assigned to the phenyl group of styrene and at 1724 cm(-1) assigned to the -COOH group of MAA. The H-1-NMR spectrum of the copolymer shows peaks between 7.20 and 7.27 delta assigned to the phenyl protons of styrene and at 12.5 delta assigned to the COOH proton of MAA. (c) 2005 Wiley Periodicals, Inc.