Molecular Restructuring Kinetics and Low-Velocity Wetting of n-Alkane Rotator Phases by Polar Liquids

Abstract

Advancing and receding contact angles were measured on n-alkane surfaces at substrate speeds below 300 μm/s for dimethyl sulfoxide, formamide, ethylene glycol, 2,2‘-thiodiethanol, and glycerol. The existence of plastic crystalline or rotator phases prior to the melting transition for n-alkane solids was utilized to provide a range of substrate molecular freedom. Contact angles for liquid-substrate combinations demonstrated velocity dependence for high interface velocities resulting in steady-state hysteresis. For measurements made on a commercial paraffin substrate in transition between the ordered crystalline and RII rotator phases corresponding to a high mechanical loss tangent, contact angles converged to apparent equilibrium values at low velocities. However, no such relaxation was observed for the ordered crystalline phase, and thus significant differences in relaxation behavior between tested liquids on the paraffin wax were not found for substrates possessing high and low molecular freedom. Differe...