Direct observation of shear-induced orientational phase coexistence in a lyotropic system using a modified x-ray surface forces apparatus.
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.
Golan
Y
Y
Materials Department, Materials Research Laboratory, University of California, Santa Barbara, California, 93106, USA. ygolan@bgumail.bu.ac.il
Martin-Herranz
A
A
Li
Y
Y
Safinya
C R
CR
Israelachvili
J
J