Described herein is a multilayer article comprising: a. a polymer substrate comprising an abstractable atom； and b. a hydrogel coating thereon wherein the hydrogel coating has a water content of at least 10 wt % and is covalently bonded to the polymer substrate, and wherein the hydrogel coating is derived from an aqueous composition having a pH less than 9.5, the aqueous composition comprising: (a) a hydrophilic monomer selected from at least one of (meth)acrylate or (meth)acrylamide； (b) at least 0.1 wt % of a water-swellable clay； (c) a first initiator, wherein the first initiator is water-soluble and is a Type I photoinitiator； and (d) a second initiator, wherein the initiator is water-soluble and is a Type II photoinitiator； and (e) an acid.
