Crosslinkable prepolymers from a hydrophilic monomer and a hydrophobic crosslinker

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.