A method for preparing an environmentally-responsive hydrogel for implantation in an animal comprising: a) combining at least one ethylenically unsaturated macromer, at least one macromer or monomer comprising at least one ionizable functional group, at least one polymerization initiator, and at least one solvent to prepare a hydrogel; b) treating said hydrogel to prepare an environmentally-responsive hydrogel that is responsive at physiological conditions.