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Molecular dynamics (MD) simulations were performed to investigate the geometric effect of nanostructured substrates on adsorptive behavior of potassium stearate monolayers. A typical protective coating, diamond-like carbon (DLC), was employed as adsorptive substrates. For the substrates with square grooves, complete penetration of molecules can only occur under large width and small depth. The occurrence of partial penetration would make monolayer atoms away from substrate surfaces and therefore induce weak substrate-molecules interactions. Compared with the square groove bottoms, monolayers are much more strongly adsorbed to the groove concave corners. For substrates with triangle and semi-circle grooves, complete penetrations are achieved in both cases and thus monolayer atoms can interact with the whole groove surface. The effect of substrate morphology on monolayer adsorption would be sufficiently weakened by the decrease of geometric size, and the surface adsorptivity of semi-circle grooves with large radius is similar to that of the smooth surface. The results indicate that the substrates with triangle grooves have better adsorptivity than other morphologies. • Size effect of nanostructured diamond-like carbon substrates on adsorption of potassium stearate monolayers was studied using MD simulation. • Geometric size of surface morphologies and amorphous atomic arrangement will significantly influence the molecular adsorption. • The monolayer-to-substrate adhesion at concave corners is much stronger than other positions within grooves. • Complete penetration of monolayers is achieved in all the morphology sizes for triangle grooves and semi-circle grooves. [ABSTRACT FROM AUTHOR]

Molecular dynamics (MD) simulations were used to provide insights into the influence of nano-scale surface morphology on adsorptive behavior of Potassium stearate molecules on diamond-like carbon (DLC) substrates. Particular focus was given to explain that how the distinctive geometric properties of different surface morphologies affect the equilibrium structures and substrate-molecules interactions of monolayers, which was achieved through adsorptive analysis methods including adsorptive process, density profile, density distribution and surface potential energy. Analysis on surface potential energy demonstrated that the adsorptivity of amorphous smooth substrate is uniformly distributed over the surface, while DLC substrates with different surface morphologies appear to be more potentially corrugated, which improves the adsorptivity significantly. Because of the large distance of molecules from carbon atoms located at the square groove bottom, substrate-molecules interactions vanish significantly, and thus potassium stearate molecules cannot penetrate completely into the square groove. It can be observed that the equilibrium substrate-molecules interactions of triangle groove and semi-circle groove are much more powerful than that of square groove due to geometrically advantageous properties. These findings provided key information of optimally design of solid substrates with controllable adsorptivity. [ABSTRACT FROM AUTHOR]

Molecular dynamics (MD) simulations were performed to investigate the adsorption of potassium stearate molecules on diamond-like carbon (DLC) substrate. The effects of non-bonded interactions and confinement conditions on the adsorption were investigated. The confinement conditions performed herein were achieved by imposing a Z-direction constraint on the movement of molecules in the initial stage of adsorption, and then releasing the molecules from the constraint gradually. Our simulation results show that the polar end groups of molecules tended to accumulate during the adsorption, and the final distribution of adsorptive film without confinement was irregular. Under confinement conditions, the adsorptive film was evenly distributed on the substrate after reaching its equilibrium configuration, and the final inter-subsystem potential of the substrate on adsorptive film was obviously decreased as compared with the results without confinement. These findings provided an effective approach for promoting the adsorption of molecules. [ABSTRACT FROM AUTHOR]