Relation between the adhesion strength and interfacial width for symmetric polystyrene bilayers

Polystyrene (PS) bilayers were prepared and were adhered at a temperature between the surface and bulk glass‐transition temperatures for a given time. Then, the interfacial adhesion strength ( G L ) was examined with a conventional lap‐shear measurement. G L first increased with increasing adhesion time and then reached a constant value. This result implied that the segments moved across the interface, to a certain depth, even at a temperature below the bulk glass‐transition temperature. To confirm this, the interfacial evolution for the PS/deuterated PS bilayers was examined with dynamic secondary‐ion mass spectrometry. The G L value was linearly proportional to the thickness of the interfacial adhesion layer. Finally, we propose a strategy for regulating the adhesion strength based on the chain‐end chemistry.