The IR spectra of styrene-acrylic acid copolymer-supported neodymium complexes were investigated. The complexes possess a structure of bidentate carboxylate groups and the Nd-O bond in the complexes is rich in covalency. The general feature of the butadiene polymerization catalyzed by the supported neodymium complexes as well as the relationship between the nature

constitution of the complexes and the catalytic activity were studied. The copolymers prepared by solution polymerization in THF or dioxane were better supporter for the synthesis of highly active supported catalyst. The polymer-supported neodymium complexes containing about 12wt% functional group-COOH gave optimum catalytic actiity at Nd/-COOH molar ratio=0.20.