Acrylic acid carboxylated acrylic rubber (ACM) and itaconic acid carboxylated acrylic rubber were prepared by Co-60-gamma-ray-induced emulsion copolymerization. The polymers were characterized using FTIR and C-13 NMR spectroscopies. The acid value was determined with nonaqueous titration method. The molecular weight and the polydispersity index of the polymers were measured using gel permeation chromatography. The influence of the cure-site (carboxyl) on the vulcanization and mechanical properties of the ACM was researched by means of rheometric study, gel fraction analysis, mechanical property tests, and dynamic mechanical thermal analysis. The results show that the crosslink density of polymers increases with amounts of the carboxyl cure-site. The itaconic acid carboxylated ACM has better cure characteristics and mechanical properties than the acrylic acid carboxylated ACM has. In addition, the comparison of ACM prepared by Co-60-gamma-ray-induced polymerization with ACM prepared by chemical-initiator-induced polymerization has been investigated. (c) 2006 Wiley Periodicals, Inc.