The X-ray Surface Forces Apparatus: Structure of a Thin Smectic Liquid Crystal Film Under Confinement

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Science  24 Jun 1994:
Vol. 264, Issue 5167, pp. 1915-1918
DOI: 10.1126/science.264.5167.1915


An x-ray surface forces apparatus for simultaneously measuring forces and structures of confined complex fluids under static and flow conditions is described. This apparatus, combined with an intense synchrotron x-ray source, allows investigation of molecular orientations within a thin liquid crystal film confined between two shearing mica surfaces 3900 angstroms apart. The layer-forming smectic liquid crystal 8CB (4-cyano-4'-octylbiphenyl) adopted a series of distinct planar layer orientations, including the bulk flow-forbidden b orientation.