Effect of Molecular Weight of Pressure-sensitive Adhesive to Peeling Phenomenon between Adhesive and Silicon Wafer by Molecular Dynamics Simulations

Abstract

We have investigated the peeling behavior between pressure-sensitive adhesive and silicon wafer by using molecular dynamics method. Our aim is to clarify the effect of the molecular weight of adhesives to the peeling behavior. We have conducted peeling simulations with various molecular weight of adhesives and various surface roughness of silicon substrate as modeled by amorphous SiO₂. We focus on the stress-displacement curve, the maximum value of peeling stress and the energy required for the peeling. It was found that the larger molecular weight and larger surface roughness induced larger peeling energy. Peeling energy is dependent on the interface bonding status. On the contrast, maximum value of peeling stress partially correlates with the molecular weight. From the detailed observation of peeling process, it was found that peeling stress is dependent on the network of adhesive molecule chains. The maximum value of the peel stress increases as the number of partial molecular chains constrained to the substrate, and the number of the partial molecular chains connected to the constrained molecular chain via increase of cross-links. In addition, the number of interfaces of the connected partial molecular chain increases the maximum peeling stress. Our results provide a new insight to the design of adhesive.