Synthesis and structure–property relationships of UV-curable urethane prepolymers with hard–soft–hard blocks

UV-curable urethane prepolymers derived from diisocyanates, rigid diols, and polypropylene glycols of different molecular weights and end-capped with 2-hydroxylethyl methacrylate were prepared by stepwise addition reactions. These prepolymers have the common structure, HEMA-hard segment-soft segment-hard segment-HEMA. As the weight ratio of soft segment to hard segment and thus the rigidity varied, the cured films from these prepolymers exhibited a wide range of mechanical and other key properties such as oxygen permeability.