Effects of surface affinity on the ordering dynamics of self-assembled monolayers of chain molecules: Transition from a parallel to a perpendicular structure

Simulation Study of the Effects of Nanoporous Structures on Mechanical Properties at Polymer-Metal Interfaces

We investigated the effect of nanopores on the adhesion behavior at polymer-metal interfaces by molecular dynamics simulation. The effects of shear and extension behavior were examined. In the shear mode, samples with porous substrates showed larger shear forces than those with flat substrates. Meanwhile, the breaking strengths in the extension mode were almost the same for systems with flat and porous substrates. The similar behavior in the extension mode was ascribed to the formation of voids in the polymer layer, which was related to the increase of total system volume and not affected by the presence of pores. We also investigated the relationship between the mechanical properties of polymer-metal interfaces in the shear mode and pore size in detail. Even a very shallow pore with a depth of 0.5 nm produced a large shear force comparable to that of a pore with a depth of 2.0 nm. The shear force increased gradually as the pore diameter became wider. These simulation results revealed that the adhesion forces between polymers and rough metal surfaces are not simply related to the interface area but depend on the pulling mode, pore size, and polymer chain length in a complicated manner.

Diffusion Influenced Adsorption Kinetics

When the kinetics of adsorption is influenced by the diffusive flow of solutes, the solute concentration at the surface is influenced by the surface coverage of solutes, which is given by the Langmuir-Hinshelwood adsorption equation. The diffusion equation with the boundary condition given by the Langmuir-Hinshelwood adsorption equation leads to the nonlinear integro-differential equation for the surface coverage. In this paper, we solved the nonlinear integro-differential equation using the Grünwald-Letnikov formula developed to solve fractional kinetics. Guided by the numerical results, analytical expressions for the upper and lower bounds of the exact numerical results were obtained. The upper and lower bounds were close to the exact numerical results in the diffusion- and reaction-controlled limits, respectively. We examined the validity of the two simple analytical expressions obtained in the diffusion-controlled limit. The results were generalized to include the effect of dispersive diffusion. We also investigated the effect of molecular rearrangement of anisotropic molecules on surface coverage.