Dynamic Wetting and Dewetting of a Low-Energy Surface by Pure Liquids

A high resolution optical method was used to acquire contact angle−velocity data for hexadecane and octamethylcyclotetrasiloxane (OMCTS) advancing and receding on a smooth, virtually homogeneous fluorinated surface. The predictive abilities of the hydrodynamic, molecular−kinetic and combined molecular−hydrodynamic models of wetting dynamics were compared. In this context the behavior of hexadecane and OMCTS were distinctly different. Where application of the molecular−kinetic model is most appropriate (hexadecane advancing) the motion of the contact line does agree well with the molecular length. However when hydrodynamics play a role and the combined molecular−hydrodynamic model is required, then the characteristic lengths obtained greatly exceed molecular dimensions.