title: Direct observation of shear-induced orientational phase coexistence in a lyotropic system using a modified x-ray surface forces apparatus.
abstract: The second generation x-ray surface forces apparatus (XSFA-II) allows for the first time simultaneous in situ small-angle x-ray scattering and surface force measurements. We have used the XSFA-II to monitor shear-induced orientational transitions in a lyotropic model lubricant system. Upon applying small shear amplitudes (approximately 20 micrometer) to a relatively thick (approximately 800 micrometer) film, we observed evidence for the formation of an orientational boundary layer at the shearing surface. Time-resolved x-ray diffraction revealed the gradual transition to shear-favored orientation by growth of the boundary layer.
authors.affiliation: Materials Department, Materials Research Laboratory, University of California, Santa Barbara, California, 93106, USA. ygolan@bgumail.bu.ac.il
authors.forename: Y
authors.initials: Y
authors.lastname: Golan
authors.forename: A
authors.initials: A
authors.lastname: Martin-Herranz
authors.forename: Y
authors.initials: Y
authors.lastname: Li
authors.forename: C R
authors.initials: CR
authors.lastname: Safinya
authors.forename: J
authors.initials: J
authors.lastname: Israelachvili