[SY-O5] Efficient evaluation of adhesion free energy between a liquid and polymer-grafted substrate
Relating to recent rapid advancement in substrate-decoration technique such as the one using the Self-Assembled Monolayers, there exist strong demands to predict the adhesion free energy between a complex liquid and polymer-grafted substrate. In principle, the adhesion free energy can be evaluated through the molecular simulation by integrating the work required to separate the liquid from the substrate. In former methods for the work of adhesion, a planar shape potential is introduced and the work of adhesion is calculated through integrating the force exerted on the potential from liquid molecules when liquid molecules are separated from the solid surface by gradually shifting the potential origin. These methods work well for sufficiently flat solid substrate. However, they are inefficient for a polymer-grafted substrate because it becomes necessary to shift the potential over a long distance.
Motivated by that, we propose a novel method to efficiently evaluate the work of adhesion of the interface between a liquid and a polymer-grafted surface. In the present method, a set of spherical potentials whose centers are set at the atomic positions of either polymer or substrate are introduced instead of a planar potential. It enables efficient separation of the liquid molecules from the polymer-grafted substrate. Moreover, potential-parameter update schemes are carefully chosen to suppress sharp variation in the force exerted on the potential and thereby to minimize the number of integration points.
The present method is applied to the interface between a water and a gold substrate on which poly(ehtylene oxide)s (PEOs) are grafted. Then, we find that the work of adhesion tends to become large at the intermediate density of PEO. This tendency is related to the number of water molecules accessible to oxygen atoms in PEO.
Motivated by that, we propose a novel method to efficiently evaluate the work of adhesion of the interface between a liquid and a polymer-grafted surface. In the present method, a set of spherical potentials whose centers are set at the atomic positions of either polymer or substrate are introduced instead of a planar potential. It enables efficient separation of the liquid molecules from the polymer-grafted substrate. Moreover, potential-parameter update schemes are carefully chosen to suppress sharp variation in the force exerted on the potential and thereby to minimize the number of integration points.
The present method is applied to the interface between a water and a gold substrate on which poly(ehtylene oxide)s (PEOs) are grafted. Then, we find that the work of adhesion tends to become large at the intermediate density of PEO. This tendency is related to the number of water molecules accessible to oxygen atoms in PEO.