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 (e.g. glucose). They also possess the necessary physical properties of an outer polymeric biosensor membrane.