Polyurethanes of different compositions were synthesized by chain extending the prepolymer formed by the reaction of poly(tetramethylene oxide)glycol and tolylene diisocyanate with 3,4-dihydroxycinnamic acid. The polyurethanes were characterized using Fourier transform infra-red and Fourier transform nuclear magnetic resonance spectroscopies. The molecular weights of the polymers were determined using gel permeation chromatography. The polyurethane anionomers showed typical polyelectrolyte behaviour. The glass transition temperatures of the polyurethanes and their anionomers were determined by differential scanning calorimetry. The thermal stabilities of the polymers were evaluated using a thermogravimetric analyser.