The invention provide a class of chain-extended polysiloxane crosslinkers which comprises (1) at least two polysiloxane segments, wherein each pair of adjacent polysiloxane segments is linked by one divalent organic radical which includes at least one pendant hydrophilic group (hydroxyl and/or carboxyl groups) or at least one dangling hydrophilic polymer chain and a di-thioether linkage —S-DR-S— in which DR is a divalent organic radical； and (2) two terminal ethylenically unsaturated groups. The present invention is also related to a polymer comprising crosslinking units derived from chain-extended polysiloxane crosslinker of the invention and to ophthalmic lenses comprising such a polymer.
