Photoactive additives, such as cross-linkable polycarbonate resins, are disclosed. The additive is formed from the reaction of a monohydroxybenzophenone, a dihydroxybenzophenone, a diol chain extender, and one or more linker moieties having functional groups that react with the phenolic groups on the other ingredients. If desired, a secondary linker moiety and/or an end-capping agent can be used. When added to a base polymeric resin, the photoactive additive permits crosslinking when exposed to ultraviolet light.