Impacts of Chain Adsorption on Adhesion Strength at Solid Interfaces

Adhesion technology using polymer materials has attracted attention due to its lightweight nature and high processability in structural materials, particularly mobility applications. Adhesive design relies more on practical knowledge than on scientific evidence. For instance, it is empirically known that adhesion strength increases over time after contact. This phenomenon could result from the adsorption of polymer chains onto the solid surface. However, how the adsorption states of polymer chains influence their adhesion properties remains unclear. In this study, to clarify this issue, we systematically changed the thermal annealing time of polymer thin films on a substrate and investigated the time evolution of adhesion properties in comparison with that of the thickness of adsorbed layers. The interfacial adhesion strength increased with annealing time, and its time evolution was consistent with the growth of the adsorbed layer. In addition, the strength depended not on the molecular weight but on the interaction energy between segments and the substrate, as well as the stereoregularity of chains. Thus, the controlling factors of interfacial adhesion strength included the number of contact points of chains on the solid, interaction energy, and differences in chain conformations.