Structural investigation of diglycerol monolaurate reverse micelles in nonpolar oils cyclohexane and octane.
Structure of diglycerol monolaurate (abbreviated as C(12)G(2)) micelles in nonpolar oils cyclohexane and n-octane as a function of compositions, temperatures, and surfactant chain length has been investigated by small-angle X-ray scattering (SAXS). The SAXS data were evaluated by the generalized indirect Fourier transformation (GIFT) method and real-space structural information of particles was achieved. Conventional poly(oxyethylene) type nonionic surfactants do not form reverse micelles in oils unless a trace water is added. However, present surfactant C(12)G(2) formed reverse micelle (RM) in cyclohexane and n-octane without addition of water at normal room temperature. A clear signature of one dimensional (1-D) micellar growth was found with increasing C(12)G(2) concentration. On the other hand, increasing temperature or hydrocarbon chain length of surfactant shorten the length of RM, which is essentially a cylinder-to-sphere type transition in the aggregate structure. Drastic changes in the structure of RM, namely, transition of ellipsoidal prolate to long rod-like micelles was observed upon changing oil from cyclohexane to octane. All the microstructural transitions were explained in terms of critical packing parameter.
Graduate School of Environment and Information Sciences, Yokohama National University, Hodogaya-ku, Yokohama, Japan.
Lok Kumar
LK
Shrestha
Kenji
K
Aramaki
D003510:Cyclohexanes / Q000737:chemistry*; D004075:Diglycerides / Q000737:chemistry*; D008823:Micelles; D015394:Molecular Structure; D009795:Octanes / Q000737:chemistry*; D012542:Scattering, Radiation; D013501:Surface-Active Agents / Q000737:chemistry; D013696:Temperature; D014961:X-Ray Diffraction
D003510:Cyclohexanes; D004075:Diglycerides; D008823:Micelles; D009795:Octanes; D013501:Surface-Active Agents; C506365:Cyclohexane; C026728:octane