Polyurethane (PU) anionomers were synthesized from phthalic anhydride, neopentyl glycol, isophorone diisocyanate and dimethylolpropionic acid (DMPA) according to a prepolymer-mixing process. Emulsion characteristics and basic structure-property relationships of the emulsion-cast film were studied with regard to the DMPA concentration, degree of neutralization (DN), prepolymer molecular weight (M(pre)) and the extender functionality (f). Average particle size decreased and emulsion viscosity increased with increasing DMPA concentration and DN. The major glass transition temperature of the PU (transition of the phase rich in soft segments (T-gs)) increased with increasing DMPA concentration and f and decreased with increasing M(pre) and DN. The increase was interpreted in terms of soft segment-hard segment phase mixing, due to the increased hard fraction (DMPA) and increased cohesion of PU (f), whereas the decrease was interpreted in terms of increased phase separation (M(pre)) and increased hard segment cohesion (DN).