New ester and acid functionalized diene-based polymers were successfully synthesized by bulk and solution homopolymerizations and copolymerizations with styrene. The ester-containing diene chosen, 2,3-bis(4-ethoxy-4-oxobutyl)-1,3-butadiene, followed typical free-radical kinetics. For the bulk polymerizations, number-average molecular weights of 13 x 10(3)-80 x 10(3) g/mol and polydispersities of 2.0-4.0 were seen. Solution polymerizations did not exhibit a chain transfer to solvent effect, but rather showed a dependence on chain transfer to monomer, with the highest molecular weight of 96 x 10(3) g/mol obtained in cumene. Copolymerizations with styrene led to random copolymers, with the expected increase in the glass transition temperature as the styrene concentration increased. Functional modification of the homopolymer from a diester to a diacid was obtained in quantitative yields via saponification in tetrahydrofuran and water. This modification elevated the glass transition temperature of the polymer from -37 degreesC (diester) to 67 degreesC (diacid). The diacid polymer was only soluble in highly polar solvents (DMSO, THF) but was soluble in water while in the carboxylate form. All polymers exhibited 100% 1,4-microstructure as determined by H-1 NMR.