Issue 20, 2009

Unprecedented microemulsion boosting effect induced by a charged diblock copolymer: bending modulus and curvature frustration of the surfactant film

Abstract

Single-phase microemulsions made of comparable amounts of water and alkane cannot be stabilized unless a large proportion of surfactant is used. Typically 10 to 30% nonionic surfactants such as n-alkylpolyglycol ethers are required to form such phases. Over the past 15 years, several authors have shown that this proportion can be significantly reduced by adding minute amounts of neutral diblock copolymers. However, though the surfactant film elastic properties seem to play a role in this so-called efficiency boosting effect, there is no clear agreement about the influence of the copolymer on bending properties, and about the correlation between those properties and the boosting effect. We present in this paper an original experimental occurrence of the boosting effect by using charged diblock copolymers. Based on a combination of various experimental techniques, an unprecedented swelling is evidenced and discussed in terms of variations of bending modulus. In particular an expression of the microemulsion free energy density proposed by Andelman et al. is used to correlate successfully the surfactant film bending modulus to the boosting. A curvature “frustration” between surfactant and copolymer is also pointed out as a possible contribution to the boosting effect.

Graphical abstract: Unprecedented microemulsion boosting effect induced by a charged diblock copolymer: bending modulus and curvature frustration of the surfactant film

Article information

Article type
Paper
Submitted
12 Mar 2009
Accepted
06 Jul 2009
First published
11 Aug 2009

Soft Matter, 2009,5, 4006-4014

Unprecedented microemulsion boosting effect induced by a charged diblock copolymer: bending modulus and curvature frustration of the surfactant film

F. Marchal, P. Guenoun, J. Daillant, D. W. Holley and J. W. Mays, Soft Matter, 2009, 5, 4006 DOI: 10.1039/B904990H

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