Alignment of hexatic Langmuir monolayers under shear

We have studied the structural changes that fatty acid monolayers in the Ov phase undergo when a simple shear flow is imposed. A strong coupling is re vealed by the changes in domain structure that are observable using Brewste r angle microscopy, suggesting the possibility of shear alignment. The depe ndence of the alignment on the molecular polar tilt proves that the mechani sm is different than in nematic liquid crystals. We argue that the degenera te lattice symmetry lines of the underlying pseudohexagonal lattice align i n the flow direction, and we explain the observed alignment angle using geo metrical arguments.