The phase separation behavior of polymer blends modified by copolymer additives has been studied using light scattering techniques. Block and random copolymers with equal styrene and butadiene content as well as a random copolymer with unequal monomer composition were used as additives at a concentration of 2.5% (w/w). The symmetric additives lowered the phase boundary with increasing concentration while the asymmetric additive destabilized the phase boundary. The data demonstrate a slowing of the kinetics with the addition of any of the copolymers. In comparison to the binary blend, droplet sizes in the early stage were smaller with added symmetric block copolymer and larger with added asymmetric random copolymer. Scaling analysis of the intermediate stage kinetics showed some deviations relative to binary scaling results. Deviations from Pored's law indicate that modifications to the interfacial boundary are most notable for the asymmetric random copolymer. Self-similarity was seen to hold for all of the systems.