The characterization of the interfacial surface of a dimethoxysilyl-terminated polypropylene oxide (DMSi-PPO)/diglycidylether of bisphenol A (DGEBA) system, which has the phase structure of DGEBA particles in a DMSi-PPO matrix, was investigated by using model joints with polymeric substrates. The surface free energy (gamma) of the DMSi-PPO/DGEBA system had varied with the gamma of each substrate. When the system contacted to low surface free energy materials such as Teflon, polypropylene, and polyethylene, the gamma of the system showed about 14.3-31.6 mJ/m(2); on the other hand, when the system contacted to high surface free energy substrates such as polyethylene-telephthalate and polyimide, the gamma of the system showed 50.4 and 64.6 mJ/m(2), respectively, because the concentration of the DGEBA as a polar component in the system changed around these interfaces. In the low surface energy substrates used, the actual peel adhesion energy value was in good agreement with the thermodynamic work of adhesion (Wa) determined independently. However, in the high surface energy materials used, the peel adhesion energies were 10(3)-10(4) times larger than Wa because the energy was dissipated viscoelastically at the jointed points.