Pengtao Yue, James J. Feng, Chun Liu & Jie Shen
J. Colloid & Interface Sci. 290, 281-288 (2005)
Abstract - Nematic-isotropic interfaces
exhibit novel dynamics due to anchoring of the liquid crystal molecules
on the interface. The objective of this study is to demonstrate the
consequences of such dynamics in the flow field created by an elongated
nematic drop retracting in an isotropic matrix. This is accomplished by
two-dimensional flow simulations using a diffuse-interface model. By
exploring the coupling among bulk liquid crystal orientation, surface
anchoring and the flow field, we show that the anchoring energy plays a
fundamental role in the interfacial dynamics of nematic liquids. In
particular, it gives rise to a dynamic interfacial tension that depends
on the bulk orientation. Tangential gradient of the interfacial tension
drives a Marangoni flow near the nematic-isotropic interface. Besides,
the anchoring energy produces an additional normal force on the
interface that, together with the interfacial tension, determines the
movement of the interface. Consequently, a nematic drop with planar
anchoring retracts more slowly than a Newtonian drop, while one with
homeotropic anchoring retracts faster than a Newtonian drop. The
numerical results are consistent with prior theories for interfacial
rheology and experimental observations.