Photoactive additives are disclosed. The additive includes a benzophenone having at least one substituent that comprises a divalent linker and a linking group, wherein the linking group is a carboxyl group, ester group, or acid halide group. The additive can be a polymer, an oligomer, or a compound. When added to a base polymeric resin, the photoactive additive permits crosslinking upon exposure to ultraviolet light.