ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
We have used high-resolution magnetic birefringence to study very dilute mixtures of the nonionic surfactant pentaethylene glycol mono-dodecyl-ether (C12E5) in water at fields to H=18 T. The induced refractive index anisotropy Δn shows distinct H dependencies in the Lα-lamellar and L3-"sponge'' phases, and demonstrates that these are separated by a two-phase coexistence region. In the L3 phase and for surfactant concentrations γ(approximately-equal-to)0.02 (the vicinity of the Lα phase terminus), we observe a sharp change in the magnitude and H dependence of Δn. A quantitative analysis shows this to be consistent with a crossover from a highly-connected "symmetric sponge'' to a droplet or "asymmetric sponge'' structure as a function of γ, a result previously suggested by neutron scattering and electrical conductivity measurements [R. Strey, R. Schomacker, D. Roux, F. Nallet, and U. Olssen, J. Chem. Soc. Faraday Trans. II 86, 2253 (1990)]. Finally, for γ(approximately-greater-than)0.02 and at large H, we present evidence of a field-induced transformation of the L3 structure. © 1995 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.469870
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