Photon Factory Activity Report 2016 #34 (2017)

BL-15A2/2015G547

Orientation Control of Inverse Bicontinuous Cubic Phase by using Shear Alone:
Effects of Strain Amplitude of “MAOS” and Replacement of LAOS by Steady Flow.
Natsume Kira, Youhei Kawabata, and Tadashi Kato*
Tokyo Metropolitan University, Tokyo 192-0397, Japan
1 Introduction
The inverse bicontinuous cubic phase (V2 phase) isone of the lyotropic phases consisting of bilayer networks
with a long-range order. Recently, we have performed
simultaneous measurements of rheology/small-angle Xray scattering (rheo-SAXS) for V2 phase with a spacegroup Ia3d formed in a nonionic surfactant (C12E2)/watersystem [1]. It has been found that the application of thelarge amplitude oscillatory shear (LAOS) with the strain
amplitude (0) of about 20 induces grain refinement,
whereas sample orientation occurs by applying the“medium” amplitude oscillatory shear (“MAOS”) whose
strain amplitude is much smaller than the LAOS but stillin the nonlinear regime just after the LAOS. In thesestudies, the frequency of the MAOS has been chosen tobe much higher than of the LAOS. In the present study,
the frequency of the MAOS has been set to the samevalue as the LAOS and studied relations between thestrain amplitude of the MAOS and the sample orientation.
We have also examined effects of replacing the LAOS bysteady flow with various shear rates.

between the detectors. For the “ideal” powder sample, becomes 1. When all the peaks are included within (n/3) , on the other hand, α should be 2.5 because we set
 = /18. Time evolution of  is shown in Figure 1a.
For the steps ① , ③ , ⑤ , and ⑦ ,  is close to 1 asexpected. The results for the steps ②, ④, ⑥, and ⑧
indicate that the sample orientation can occur even if thefrequencies of the LAOS and MAOS are the same andthat the large difference in the strain amplitude between
them should be important for the sample orientation.
Figure 1b shows effects of replacing the LAOS by thesteady flow (the steps ①, ③, ⑤, and ⑦). The conditionsof the MAOS are the same as in the previous study. It canbe seen from the figure that the higher the shear rate of
the steady flow just before the MAOS, the higher theorientation degree during the MAOS. These results
suggest that the grain refinement processes in the steadyflow strongly affects the sample orientation during theMAOS applied after the steady flow.

2 Experiment
Rheo-SAXS measurements were performed on thebeamline 15A2 by using a stress-controlled rheometer
AR550 (TA Instruments). The details of the shear cell
have been reported previously. The scattered beam wasrecorded with the camera length of 2.6 m using thePILATUS3 2M. The approximate q range is from 0.1 to2.4 nm-1. The exposure time was 10 s.
3 Results and Discussion
Figure 1a shows time evolution of 2-D SAXS patterns
in the tangential configuration with variation of theangular frequency ( ) and the strain amplitude (0) of theoscillatory shear (see the table above the figure). In thesteps ①, ③, ⑤, and ⑦, we applied the LAOS with thesame  and 0. In the steps ②, ④, ⑥, and ⑧, on theother hand, we applied the MAOS with the same value of as the LAOS except for the step ② whose conditions
are the same as in the previous study (the steps ① and ②
were added for comparison). For quantitative discussion,
we use the degree of the orientation α defined by3( n / 3)  (n / 3)  I ( ) d8
1n 0 
1I ( ) d  2 (1)where I() is the peak intensity of the (211) reflection at
the azimuthal angle  ( = 0 corresponds to the velocitygradient direction). The peaks for n = 4 and 5 wereexcluded because they are superimposed to the gap

Fig. 1 Time evolution of 2-D SAXS patters in thetangential configuration and the degree of orientation
obtained from the peak intensity of the (211) reflection
using Eq. 1 with the change in the shear conditions shownin the tables where  and 0 in the panel (a) are theangular frequency and the strain amplitude of theoscillatory shear, respectively. In the table of the panel(b), the shear rates of the steady flow are indicated.
References[1] M. Yamanoi, Y. Kawabata, and T. Kato, Langmuir , 32,2863 (2016).

* kato-tadashi@tmu.ac.jp