Polymeric compositions that include polyurethane polymers derived from a polyisocyanate compound and a polyactive hydrogen compound. The polyurethane compound is at least partially endcapped with a group including at least one antimicrobial quaternary ammonium compound. The polymeric composition of the present invention is capable of forming a self-supporting film. The polymeric compositions are suitable for coating substrates to effectively kill or prevent the growth of microorganisms such as bacteria, mold, mildew, algae fungi and the like. The polymeric compositions are particularly useful for protecting construction materials used in moist, outdoor environments to prevent discoloration or decay from microorganisms and for surfaces in health care facilities to mitigate the spread of pathogens.