Local dynamics of micelles of new long-chain surfactants in aqueous media |
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Authors: | M V Motyakin L L Yasina A M Wasserman L Z Rogovina V N Matveenko |
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Institution: | (1) Semenov Institute of Chemical Physics, Russian Academy of Sciences, ul. Kosygina, 4, 119991 Moscow, Russia;(2) Department of Chemistry, Moscow State University, Moscow, Russia;(3) Volgograd State Technical University, Volgograd, Russia;(4) Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow, Russia |
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Abstract: | The molecular dynamics, organization, and phase state of aqueous solutions of new long-chain cationic surfactants with saturated
hydrocarbon radicals (from C16 to C22) containing one or two hydroxyl groups in their polar heads are studied by the spin-probe EPR spectroscopy. In the region
of micellar solutions, local mobility of surfactant molecules slightly changes with an increase in the length of hydrocarbon
radical, whereas the order parameter of micelles increases notably. The addition of two hydroxyl groups to the polar part
of long-chain (C
22) surfactant molecule considerably decreases local mobility and increases the ordering of micellar system compared to the
micelles of analogous surfactant with one hydroxyl group. Phase transition from micellar to a solid state is observed in this
system with a decrease in temperature. The addition of KCl to aqueous surfactant solution lowers the local mobility, increases
the order parameter of micelles, and can cause changes in the phase state of a system. In the presence of salt, the correlation
time of probe rotation and its order parameter depend on surfactant concentration. Apparently, this is explained by changes
in the shape of micelles upon variations in surfactant concentration. |
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