Patent ID: 7091283

Claim:
A crosslinkable or polymerizable prepolymer that is obtained by (a) copolymerizing at least one hydrophilic monomer having one first ethylenically unsaturated group and at least one crosslinker comprising two or more second ethylenically unsaturated groups in the presence of a chain transfer agent comprising a chain transfer group and a first reactive group to obtain a copolymerization product with first reactive groups, wherein said at least one crosslinker is a polysiloxane, a perfluoroalkyl polyether, or a polysiloxane/perfluoroalkyl polyether block copolymer, wherein the hydrophilic monomer is a monomer which, when polymerized, gives a homopolymer which is water-soluble or can absorb at least 10% by weight of water; and (b) reacting an organic compound with the copolymerization product to form the crosslinkable or polymerizable prepolymer having third ethylenically unsaturated groups, wherein the organic compound comprises a third ethylenically unsaturated group and a second reactive group, wherein the second reactive group of the organic compound reacts with one of the first reactive groups of the copolymerization product, wherein said crosslinkable or polymerizable prepolymer can be crosslinked or polymerized to form a polymeric material capable of forming a hydrogel when contacted with water.