Interfacial strengthening of different polymers has a crucial role in blending them into new materials. Healing is one way to strengthen the interface via polymer interdiffusion across and forming new entanglements. In this research work, interfacial healing kinetics and equilibrium adhesion energy of polystyrene and poly(styrene-co-methyl methacrylate) containing different amounts of methyl methacrylate comonomer were studied using asymmetric wedge cleavage test. The results showed higher interfacial adhesion energy and enhanced healing kinetics by raising styrene monomer content of the copolymer. This may be attributed to the degree of segregation, chi N, between the joint components. Interfacial healing rate depended on chi N to the power -0.1. Interfacial adhesion energy, however, scaled as chi N to the power -0.33, where chi is the Flory-Huggins interaction parameter and N is average degree of polymerization of the components. On the other hand, correlation of interfacial adhesion energy (G(IC)) with the characteristic number of interfacial entanglements (N-ent) showed a fairly good agreement with the Cole et al.' s theory. Finally, joint interfacial adhesion energy enhanced with interfacial width divided by the product of mean entanglement length and degree of segregation, chi N, irrespective of copolymer composition. (c) Koninklijke Brill NV, Leiden, 2008