Abstract: A dual reactivity crosslinking agent of formula I having at least two different reactive sites, and hydrogel materials prepared from at least two monomers with different rates of free-radical polymerization reactivity. The crosslinking agent includes at least one free-radical reactive site for vinyl-containing monomer and at least one free-radical reactive site for meth(acrylic)-containing monomer. The hydrogel materials are useful in the manufacture of biocompatible medical devices, for example, hydrogel materials having desirable physical properties useful as contact lens materials.