Nematic to smectic-<i>A</i>phase transition under shear flow: A nonequilibrium synchrotron x-ray study

Abstract

We report on x-ray scattering studies of the nematic to smectic-A transition in 4-cyano-4'-octylbiphenyl under nonequilibrium shear-flow conditions. As the transition is approached, the interplay between the viscous frictional and the flow-induced-fluctuation forces on the nematic director leads to a series of regimes whose occurrence results from the divergence in one of the viscosities due to the critical slowing down of the smectic-A order-parameter fluctuations. The experiments demonstrate that, under flow, synchrotron x-ray-diffraction techniques provide a powerful structural probe of steady-state dynamical behavior.