Modification of Elastic Constants by Charge Addition to a Nonionic Lamellar Phase
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- 作者：Nicolas Tsapis ; Raymond Ober ; and Wladimir Urbach
- 刊名：Langmuir
- 出版年：2000
- 出版时间：March 21, 2000
- 年：2000
- 卷：16
- 期：6
- 页码：2968 - 2974
- 全文大小：217K
- 年卷期：v.16,no.6(March 21, 2000)
- ISSN：1520-5827
文摘
We have investigated a lamellar phase (L
) composed of a nonionic surfactant tetraethylene glycolmonododecyl ether (C12E4), water, and decane, where a fraction of the nonionic surfactant has been replacedby an anionic one: sodium dodecyl sulfate (SDS). Changes induced by the addition of SDS have beendetermined by small-angle X-ray scattering (SAXS) and observations between crossed polarizers.Investigations have been carried out in both the water-rich and the oil-rich parts of the phase diagram.Changes in the Bragg distance, the Landau-Peierls order parameter 
and the elastic constants 
and 
have been particularly examined. In the decane-swollen L phase, SAXS spectra did not present anychanges. The Bragg distance dB, as well as , remained constant as the nonionic surfactant was replacedby the anionic one. On the other hand, the water-swollen L phase was stiffened and was decreasingdramatically with charge addition. For the same membrane volume fraction, dB decreased slightly as SDSconcentration increased. The dependence of the membrane rigidity = KdB and the smectic compressibilitymodulus with the SDS concentration have been determined and compared with recent theoreticalpredictions. It was found that increased with SDS concentration whereas presents a maximum whenthe Gouy-Chapman length is equal to the half of the water thickness.
) composed of a nonionic surfactant tetraethylene glycolmonododecyl ether (C12E4), water, and decane, where a fraction of the nonionic surfactant has been replacedby an anionic one: sodium dodecyl sulfate (SDS). Changes induced by the addition of SDS have beendetermined by small-angle X-ray scattering (SAXS) and observations between crossed polarizers.Investigations have been carried out in both the water-rich and the oil-rich parts of the phase diagram.Changes in the Bragg distance, the Landau-Peierls order parameter and the elastic constants and have been particularly examined. In the decane-swollen L phase, SAXS spectra did not present anychanges. The Bragg distance dB, as well as , remained constant as the nonionic surfactant was replacedby the anionic one. On the other hand, the water-swollen L phase was stiffened and was decreasingdramatically with charge addition. For the same membrane volume fraction, dB decreased slightly as SDSconcentration increased. The dependence of the membrane rigidity = KdB and the smectic compressibilitymodulus with the SDS concentration have been determined and compared with recent theoreticalpredictions. It was found that increased with SDS concentration whereas presents a maximum whenthe Gouy-Chapman length is equal to the half of the water thickness.