Computational Study of the Adhesion and Friction Behavior of Cross-Linked Polymer Networks

In this study, we utilized a molecular dynamics simulation approach to understand the adhesion and friction behavior of cross-linked polymer networks. We used a breakable quartic bond to model cross-linked polymers. We explored the structural characteristics and evaluated the coefficient of friction (CoF) as a function of cross-linked monomer fraction (cross-linking bond density) in 4-fold cross-linked polymer networks. To estimate the CoF, a rigid indenter was inserted to different depths of indentation. Subsequently, a constant sliding speed was applied, while keeping the depths of indentation fixed. Normal and friction forces were calculated at each depth to estimate CoF through linear curve fitting. For adhesion studies, using the force versus displacement curve, we quantified adhesion through the forces during the separation of the rigid indenter from surface of cross-linked polymeric materials while unloading after indentation into the sample. The results indicate that as the fraction of cross-linked monomers increases, the stiffness of the cross-linked network increases while the force of adhesion and CoF decrease. Additionally, increasing the depth of indentation during friction leads to higher frictional forces.