Interfacial modification and structural transitions induced by guest molecules solubilized in U-type nonionic microemulsions.

Citation:

Nissim Garti, Amar, Idit , Yaghmur, Anan , Spernath, Aviram , and Aserin, Abraham. . 2003. “Interfacial Modification And Structural Transitions Induced By Guest Molecules Solubilized In U-Type Nonionic Microemulsions.”. Journal Of Dispersion Science And Technology, 24, 3 & 4, Pp. 397–410. doi:10.1081/DIS-120021797.

Abstract:

Alcs. and polyols are essential components (in addn. to the surfactant, H2O, and oil) in the formation of U-type self-assembled nano-structures, (sometimes called L-phases or U-type microemulsions). These microemulsions are characterized by large isotropic regions ranging from the oil side of the phase diagram up to the aq. corner. The isotropic oily solns. of reverse micelles (the concs.) can be dild. along some diln. lines with aq. phase to the direct micelles corner via a bicontinuous mesophases (i.e., 2 structural transitions). This diln. takes place with no phase sepns. or occurrence of liq. cryst. phases. The structural transitions were detd. by viscosity, cond., and pulsed gradient spin echo NMR (PGSE NMR), and are not visible to the eye. Two guest nutraceutical mols. (lutein and phytosterols) were solubilized, at their max. solubilization capacity, in the reversed micellar solns. (L2 phase) and were further dild. with the aq. phase to the aq. micellar corner (L1 phase). Structural transitions (for the 2 types of mol.) from H2O-in-oil to bicontinuous microstructures were induced by the guest mols. The transitions occurred at an earlier stage of diln., at a lower H2O content (20% aq. phase), than in the empty (blank) microemulsions (transitions at 30% aq. phase). The transitions from the bicontinuous microstructure to the oil-in-H2O microemulsions were retarded by the solubilizates and occurred at later diln. stage at higher aq. phase contents (50% aq. region for empty microemulsion and \textgreater60% for solubilized microemulsion). As a result, the bicontinuous isotropic region, in the presence of the guest mols., becomes much broader. It seems that the main reason for such guest-induced structural transitions is related to a significant flattening and enhanced rigidity of the interface. The guest mols. of the high mol. vol. are occupying high vol. fraction of the interface (when the solubilization is maximal). [on SciFinder(R)]

Last updated on 05/27/2020