It was shown that when polyurethanes designed for use in biopolymer applications were immersed in orienting fluids, significant increases in their non-dispersive surface energies took place. The kinetics of the surface energy response were found to be a function of the immersion medium＇s acid-base interaction potential. Restructuring from the as-cast state, similar to that reported for two-component polyurethane adhesives, occurs in response to thermodynamic demands and is attributable to a preferential concentration of low energy segments in the surface region. Since shifting surface energies in polyurethanes may pose problems in biological applications, an attempt was made to crosslink the surface of the polymers by the use of cold, microwave plasma discharges with Argon as the treatment gas. Plasma treatments proved to be successful, in that polyurethane surfaces so modified responded much more weakly to changes in the polarity of contact media.