The invention is related to a class of hydrophilic poly(meth)acrylamide-based copolymer comprising dangling (i.e., pendant) phosphorylcholine groups and dangling (i.e., pendant) reactive groups or chains each of which comprises one carboxyl group, one thiol group, or one primary or secondary amino group. The hydrophilic copolymers have a relatively high affinity to a base coating of a polyanionic polymer on a medical device or contact lens and are reactive towards azetidinium groups of an azetidinium-containing polymer upon heating. They can find particular use in producing water-soluble highly-branched hydrophilic polymeric material and in producing water gradient contact lenses.