a homogenous polymer composition useful as a membrane for biosensors is disclosed . the polymer composition comprises the reaction products of a diisocyanate , a hydrophilic diol or diamine , and a silicone material . an aliphatic diol or diamine may also be included . membranes prepared from the composition allow for increasing oxygen permeability and decreased analyte permeability . they also possess the necessary physical properties of an outer polymeric biosensor membrane .