Effect of urea on self-organization of sodium N-(11-acrylamidoundecanoyl)-L-valinate in water.

In this paper, the hypotheses proposed for the action of urea on the perturbation of molecular assemblies have been tested through studies of the effects of urea on the aggregation properties of a chiral surfactant, sodium N-(11-acrylamidoundecanoyl)-L-valinate in water. Surface tension, fluorescence, and circular dichroism were used to characterize the solution behavior of the amphiphile in the presence of urea. Surface tension measurement indicated decrease of critical aggregation concentration (cac) with the addition of urea in the low concentration range. Fluorescence probe studies using pyrene and 1-anilinonaphthalene indicated solubilization of urea molecules near the aggregate-water interface. Fluorescence anisotropy measurements using 1,6-diphenylhexatriene as probe molecule suggested increase of packing of the hydrocarbon chains of the amphiphiles upon addition of low concentration of urea. Dynamic light scattering measurements showed an increase of the hydrodynamic radius (R(h)) in the presence of increased concentration of urea. At higher concentrations of urea, the R(h) value decreased. Circular dichroism spectra showed the presence of chiral aggregates even in the presence of high concentration of urea.