UV-curable polyurethane prepolymers were prepared from the following components : isophorone diisocyanate, hydroxybutyl-terminated polysiloxane, and 8-hydroxyethyl methacrylate with diethylene glycol or neopentyl glycol added as an optional chain extender. These prepolymers, with hard segments of different structures, were characterized by high resolution NMR, FTIR, and gel permeation chromatography. Model oligomers were prepared to confirm the structures of the prepolymers. The structure-property relationship of cured prepolymers were determined.