Pressure sensitive adhesives can be formed using gamma irradiation. One embodiment is a pressure sensitive adhesive which is a polymeric reaction product formed by gamma ray irradiation of an emulsion composition. The emulsion composition includes water; (meth)acrylate monomer material; polar, free-radically polymerizable material that is copolymerizable with the (meth)acrylate monomer material; and at least one emulsifier