High molecular weight carboxylated polybutadienes (cPBDs) with number-average molecular weight (M-n) from 98,000 to 200,000 and carboxylic acid (COOH) contents of 0.5-10 mol % were successfully synthesized through hydrocarboxylation of polybutadienes (PBDs) at temperatures of 140-150 degrees C using PdCl2(PPh3)(2) and SnCl2. 2H(2)O catalysts. At low extents of hydrocarboxylation (COOH < 6 mol %), glass transition temperatures (T-g's) of the resulting cPBDs did not change considerably (<10 degrees C). Significant chain scission and crosslinking was not detected during the chemical modification process. Characterization of the microstructures of cPBDs by FTIR, C-13-NMR, and Raman spectroscopy showed that the carboxylic groups were incorporated on the pendant (1,2) PBD double bonds as well as the backbone (1,4) double bonds, indicating the hydrocarboxylation reaction did not solely occur at the terminal carbons of the pendant double bonds.