Poly(cis-norbornene-eco-2,3-dicarboxylic acid dialkyl esters) (alkyl = Me, Et, Pr, Bu, Pen, and Hex) are synthesized as a vinyl-type with a palladium(II) catalyst in high yield from easily prepared, pure exo-monomers. The polymers show good solubility in common organic solvents and excellent thermal stability up to 330degreesC. the polymers with alkyl groups larger than methyl exhibit a two-step thermal degradation profile of an initial thermal degradation of side-chains starting at 350degreesC, followed by thermal degradation of the norbornene backbone starting at ca. 430degreesC. the glass transition temperature decreases and the mechanical flexibility increases as the alkyl length of the side-chain increases.