Anomalous decrease in lamellar spacing by shear flow in a nonionic surfactant/water system

Tadashi Kato, Koji Minewaki, Youhei Kawabata, Masayuki Imai, Yoshiaki Takahashi

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)

Abstract

We study the effects of shear flow on the structure of a lamellar phase in a C16E7 [hepta(oxyethylene glycol)-n-hexadecyl ether]/water system (40-55 wt % of C16E7) at 70 °C using small-angle neutron scattering in the range of shear rate of 10 -3-30 s-1. At the shear rate 0.1-1 s-1, the repeat distance (d) is decreased significantly (down to about 40% of d at rest in the most significant case) and discontinuously with increasing shear rate. With the further increase in the shear rate, d increases through a sharp minimum (referred to as d*). Such a shear rate dependence of d is obtained for all the principal orientations of lamellae. As the concentration of C 16E7 decreases from 55 to 40 wt %, d increases from 6.5 to 8.5 nm at rest whereas d* remains almost constant (≅5 nm). Moreover, d* is found to be almost equal to the thickness of bilayers obtained from the line shape analysis of small-angle X-ray scattering at rest. The results strongly suggest that the water layer is excluded by shear flow and that the lamellar phase segregates into surfactant-rich and water-rich regions, although these regions do not reach macroscopic size.

Original languageEnglish
Pages (from-to)3504-3508
Number of pages5
JournalLangmuir
Volume20
Issue number9
DOIs
Publication statusPublished - 2004 Apr 27
Externally publishedYes

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

Fingerprint Dive into the research topics of 'Anomalous decrease in lamellar spacing by shear flow in a nonionic surfactant/water system'. Together they form a unique fingerprint.

Cite this