Described herein are depolymerized polystyrene resins derived from polystyrene source resins. The depolymerized polystyrene resins undergo a depolymerization in which chemical bonds are cleaved, producing depolymerized polystyrene resins of lower molecular weight. The polystyrene resins may be modified by chemical reaction with monomers, polymers, and oligomers, such as acrylates thereof. Also described are ink and coating compositions that include the depolymerized and modified polystyrene resins.