DOI: 10.1051/jp2:1996218
J. Phys. II France 6 (1996) 893-907

Alignment of Complex Fluids under Confinement and Flow

I. Koltover¹, S.H.J. Idziak¹, P. Davidson^{1, 2}, Y. Li¹, C.R. Safinya¹, M. Ruths^{3, 4}, S. Steinberg³ and J.N. Israelachvili<sup>3

1</sup>  Materials Department, Physics Department, and Biochemistry and Molecular Biology Program, University of California, Santa Barbara, CA 93106, USA
²  Laboratoire de Physique des Solides associé au CNRS, Bât. 510, Université Paris Sud, 91405 Orsay Cedex, France
³  Chemical Engineering and Materials Departments, University of California at Santa Barbara, Santa Barbara, CA 93106, USA
⁴  Department of Chemistry, University of California at Santa Barbara, Santa Barbara, CA 93106, USA

(Received 2 December 1995, received in final form 29 January 1996, accepted 20 February 1996)

Abstract
We report on a new application of the X-ray Surface Forces Apparatus [1-4] (XSFA) to the study of the alignment of complex fluid thin films under confinement and/or flow using synchrotron X-ray scattering. The smectic A liquid crystal 8CB (4-cyano-4 '-octylbiphenyl) and the hexagonal phases of a zwitterionic polyisoprene melt and of a lyotropic liquid crystal composed of sodium dodecyl sulfate (SDS), pentanol and water were investigated in the regime where the distances between the confining surfaces range from 0.4 to tens of microns. In this paper, we demonstrate that this new technique allows preparation of highly-oriented complex fluid samples suitable for high resolution X-ray diffraction and scattering studies. In addition, we have directly measured forces across thin films of 8CB using the conventional Surface Forces Apparatus (SFA). The force measurements complement well the direct X-ray imaging and provide indirect information on the sample alignment in films a few tens of Ångströms thick.

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