The present invention provides a radiation-curable prepolymer. The
radiation-curable prepolymer of the invention is prepared by reacting an
isocyanate-capped polyurethane with an ethylenically unsaturated amine or
an ethylenically unsaturated monohydroxy compound or a mixture thereof,
wherein the isocyanate-capped polyurethane is a copolymerization
production of: (a) at least one polyalkylene glycol; (b) at least one
branching agent having at least three hydroxy groups; and (c) at least
one di- or polyisocyanate. The radiation-curable prepolymer of the
invention can find use in economically producing contact lenses which
have durable, highly elastic soft contact lenses with desired physical
properties. In addition, the present invention provides method for making
a radiation-curable prepolymer of the invention and for making a medical
device, preferably an ophthalmic device, more preferably a contact lens.