Photon Factory Activity Report 2004 #22 Part B (2005)
Chemistry

15A/2003G235

Simultaneous SAXS/Rheology Measurements on a Surfactant Lamellar Phase
Tadashi KATO*, Kyoko MIYAZAKI, Yuriko KOSAKA, Youhei KAWABATA
Department of Chemistry, Tokyo Metropolitan University
1-1 Minamiohsawa, Hachioji, Tokyo 192-0397, Japan
Introduction
In recent years, much attention has been paid to theeffects of shear flow on the structure of a lamellar phase[1]. In our previous studies, we have measured smallangle neutron scattering (SANS) on the lamellar phase ofa nonionic surfactant C16H33(OC2H4)7OH (C16E7) in D2O(40-55 wt%) at 70 °C paying attention into the structural-3-1change in the relatively lower shear rate range, 10 - 30 s
-1[2]. When the shear rate increases from 0.1 to 1 s , therepeat distance (d) is decreased significantly (down toabout 40% of d at rest in the most significant case). This,
together with other results including small-angle lightscattering measurements, strongly suggests that waterlayers are excluded by shear flow and that the lamellar
phase segregates into a concentrated lamellar region and awater-rich region. It has been also found that the repeat
distance decreases discontinuously because two separated
peaks are observed in the time-resolved SANS
measurements. However, the segregation processes could
not be elucidated because it takes about 5-10 min to
obtain one SANS pattern. By using small-angle X-ray
scattering (SAXS) with the CCD camera as a detector, on
the other hand, a 2D scattering pattern can be obtained
within a second.
In the present study, we haveconstructed an apparatus for simultaneous SAXS/rheology measurements. The same sample as in theprevious SANS studies were used to compare the SANSand SAXS measurements.
Experimental
A rheometer AR550 (TA Instruments) is modified for
simultaneous SAXS/rheology experiments. Figure 1
shows schematic views of a sample cell. The cell consistsof two concentric cylinders, both of which are made ofpolycarbonate. The diameter of the inner cylinder and thegap are 25 mm and 1 mm, respectively. The temperatureof the sample is controlled by Peltier elements installed inthe rheometer through the sample jacket made of cupper.
To prevent sample evaporation, a vapor seal isincorporated in the cell.
SAXS measurements were performed on the beamline
15A. The scattered beam was recorded using the CCD
area detector covering the scattering vector range from-1
0.015 to 0.25 Å .
Results
Figure 2 shows 2-dimensional scattering patterns forthe lamellar phase of a C16E7/water system (48 wt%,70°C). These figures demonstrate that the repeat distance

x-ray

polycarbonate(thickness: 0.5 mm)sample(gap: 1mm)

x-ray
cupper25 mm
Fig. 1 Top (upper) and front (lower) views of asample cell for simultaneous SAXS/rheoloby
experiments.

Fig. 2 2-D scattering patterns for the lamellar phaseof a C16E7/water system (48 wt%, 70°C) at the-1-1
shear rate 0.3 s (left) and 1 s (right). The flow
direction is horizontal

decreases discontinuously when the shear rate increases-1-1from 0.3 s (left) to 1 s (right).
References[1] D. Roux, in “Nonequilibrium Dynamics, Metastabilityand Flow”, M. E. Cates, M. R. Evans, and P. Osborne Eds,
Institute of Physics Publishing, Bristol, Chap 7 (2000).
[2] T. Kato, K. Minewaki, Y. Kawabata, M. Imai, and Y.
Takahashi, Langmuir, 20, 3504 (2004).
* kato-tadashi@c.metro-u.ac.jp

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