Dynamic and Equilibrium Contribution of Nematic Order in Wetting and Contact Angles

A model for the dynamic contact angles and the spreading kinetics of nematic liquid crystals on a solid surface is presented for the first time using the continuum theory of liquid crystals. The equations of motion for this system are integrated for a wedge or a drop that is thin and moves slowly. The dynamic contact angle is found to depend on the capillary number that represents the importance of viscocapillarity and on the elasticity number that is the ratio between the elastic and surface forces. The model provides an explanation for the extra volume dependence that is reported in experiments, as well as one case of recoil, and for the observation that very small drops were reported to be immobile. For the first time, these previous experimental observations are shown to be due to elastic effects.