Molecular Dynamics Simulations of Equilibrium and Dynamic Contact Angles

The knowledge of both equilibrium and dynamic contact angles of fluid on materials is of fundamental importance in determining overall fluid management in porous media, and, thus, in the development of novel absorbent materials and in the design of good absorbent articles. In this work, we use molecular dynamics simulations to compute equilibrium and dynamic contact angles of water on both hydrophobic (polypropylene) and hydrophilic (cellulosic) surfaces in a direct manner. In such direct approaches all three phases are present in the simulation and the contact angles are computed from analyses of the resulting interfacial profiles. The computed contact angles depend upon the system size, and modern computing power allows simulations of large enough systems required to obtain reliable estimates. For both surfaces, the computed contact angles show reasonable agreement with known experimental data, and, thus, indicate that molecular modeling is a useful tool to determine contact angles in novel materials.