A valve in the form of a medical device, article, or implant that is composed wholly or partly of a biomaterial, the biomaterial comprising a polyurethane or polyurethane urea elastomeric composition having a plurality of soft segments and hard segments, such that the plurality of soft segments are each derived from at least one block copolymer segment of Formula 1 and optionally an additional polyol or polyamine. The valve may include a plurality ofvalve leaflets and a support structure with one or more of the valve leaflets being composed wholly or partly of the biomaterial.
