Novel calculation method for the work of adhesion of polymer-grafted surface

Molecular simulations are often used to elucidate solid-liquid interfacial properites. In the problem of adhesion, several methods to calculate the work of adhesion, which enables quantitative evaluation of the strength of the adhesion between two materials, have already been proposed. However, application of these methods is restricted to the flat solid surface. It is necessary to improve existing methods for efficient calculation of the work of adhesion for the complex solid surfaces such as polymer-grafted surfaces.
We developed the novel method to calculate the work of adhesion using molecular simulation. In this method, we introduced two techniques to perform efficient calculation for complex solid surfaces. First, liquid molecules contacted with the solid surface are separated from it using spherical potentials around atoms grafted to the surface. This enables separation of liquid molecules according to the surface structure. Second, appropriate update scheme of parameters contained in the potential is found to suppress the variation in the free energy gradient, which reduces the error of numerical integration. Using this method, we studied the dependence of hydrophilicity of the gold surface modified by poly(ethylene oxide) on the ratio of poly(ethylene oxide).