Dependence of polymer thin film adhesion energy on cohesive interactions between chains

The adhesion of supported polymer thin fi lms is predominantly infl uenced by the substrate-fi lm interfacial properties. Utilizing steered molecular dynamics simulations, here we uncover that the cohesive noncovalent forces between polymer chains in the fi lm also have a signifi cant effect on the adhesive properties of supported fi lm. We demonstrate that weaker interchain interactions, all else being the same, can induce higher adhesion energy within the interface. Three different adhesion regimes in the substrate–fi lm interaction strength profi le can be characterized by a nonlinear scaling relationship that earlier theoretical predictions currently do not capture. In the weak substrate–fi lm interaction regime, the adhesion energy of the fi lms exhibits near independence of cohesive forces, and entropic contributions to the surface free energy are consequential. In the intermediate regime, weaker fi lm cohesive forces achieve higher adhesion energy due to the ability of polymer chains to pack more effectively in the interfacial region, thereby increasing the adhesive interaction density. In the strong interaction regime, the adhesion energy increases linearly with the adhesive interaction strength because of saturation of local packing in the interfacial region. These fi ndings corroborate recent polymer wetting observations that have hinted on the importance of local relaxation and packing effects on interfacial properties.