Nonionic Reverse Micelles near the Critical Point

作者：Shrestha Lok Kumar^*; Shrestha Rekha Goswami

来源：Journal of Oleo Science, 2013, 62(12): 1073-1081.

DOI：10.5650/jos.62.1073

• nonionic surfactant
• reverse micelles
• critical point

We report shape, size, and internal cross-sectional structure of diglycerol monomyristate (C(14)G(2)) reverse micelles in n-hexadecane near the critical point using small-angle X-ray scattering (SAXS). Pair-distance distribution function, p(r), which gives structural information in real-space, was obtained by indirect Fourier transformation (IFT) method. The p(r) showed a clear picture of rodlike micelles at higher temperatures well above the critical point (micellar solution phase separates into two immiscible liquids at similar to 48 degrees C). At a fixed surfactant concentration (5% C(14)G(2)), decrease in temperature increases the micellar size monotonously and surprisingly shape of the p(r) curve at 50 degrees C; close to the critical point, mimics the shape of the two dimensional disk-like micelles indicating the onset of critical fluctuations (attractive interactions among rodlike micelles forming a weak network). A similar behavior has been observed with normal micelles in aqueous system near the critical point. When the system is heated to 60 degrees C, shape of the p(r) curve regains rodlike structure. At fixed temperature of 60 degrees C, increase in C(14)G(2) concentration induced one dimensional micellar growth. Maximum length of micelles increases from ca. 23.5 to 46.0 nm upon increasing concentration from 1 to 12% keeping cross section diameter apparently unchanged at ca. 4.0 nm.

• 出版日期2013-12