p-Perfluoro{1-[2-(2-fluorosulfonyl-ethoxy)propoxy]}ethylated poly(alpha-methyl styrene) 3 was synthesized via electron transfer of perfluoro-di{2-[2-(2-fluorosulfonyl-ethoxy)propoxy]}propionyl peroxide 2 and poly(alpha-methyl styrene) 1 at different reactant molar ratios (2 : 1). The modified polymer 3 was characterized by various techniques. The ring p-substitution was proved by FTIR and (FNMR)-F-19. The desulfonation appeared at above 124 degrees C was found by TGA. The molecular weight determined by GPC increased with the increase of reactant molar ratio, and the polydispersity values indicated there was no degradation of the parent polymer chain in the reaction. Followed by hydrolysis and acidification, the modified polymer 3 could be further quantitatively converted into its sulfonic form 4. Ion exchange capacity of novel polyelectrolyte 4 can be controlled by changing reactant molar ratio (2 : 1). (c) 2006 Wiley Periodicals, Inc.