A heterobifunctional poly(ethylene glycol) is provided having a hydrolytically degradable linkage, a first terminus comprising an acrylate group, and a second terminus comprising a target such as a protein or pharmaceutical agent or a reactive moiety capable of coupling to a target. Hydrogels can be prepared. The hydrogels can be used as a carrier for a protein or a pharmaceutical agent that can be readily released in a controlled fashion.
