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Vesicle to micelle transition in the ternary mixture of L121/SDS/D2O: NMR, EPR and SANS studies

Abstract

The subtle changes in the microstructure and dynamics of the triblock copolymer L121, (ethylene oxide)5 (propylene oxide)68 (ethylene oxide)5 i.e., E5P68E5, and sodium dodecylsulfate (SDS) system in aqueous medium have been investigated using high resolution nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR) and small-angle neutron scattering (SANS) methods. NMR self-diffusion measurements helped to understand the nature of binding of SDS with L121, and the formation of their mixed aggregates. These results showed that even at low [SDS] (~2mM), addition of L121 stabilized the dynamics of SDS. Further, the increase in [SDS] resulted in progressive changes in the diffusion behavior of both SDS and L121. 13C chemical shift analysis revealed that the preferential binding of L121 occurred on the SDS micelle surface. Deuterium (2H) NMR spin-relaxation data evidenced that the formed mixed aggregates were non-spherical in terms of relaxation rate changes, and slowed the dynamics. The rotational correlation times of mixed aggregates have been estimated from EPR analysis. SANS study indicated the presence of uni- , and multi-lamellar vesicles of L121 at low [SDS]. The vesicles transformed to mixed L121-SDS micelles in the presence of higher [SDS]. This was supported from the measurements of 2H NMR spin-relaxation and EPR rotational correlation times.

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Publication details

The article was received on 04 Oct 2017, accepted on 09 Nov 2017 and first published on 10 Nov 2017


Article type: Paper
DOI: 10.1039/C7CP06796H
Citation: Phys. Chem. Chem. Phys., 2017, Accepted Manuscript
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    Vesicle to micelle transition in the ternary mixture of L121/SDS/D2O: NMR, EPR and SANS studies

    G. K. S. Prameela, B. V. N. Phani Kumar, R. K. R. REDDY, A. Pan, J. SUBRAMANIAN, S. Kumar, V. K. Aswal, J. Kohlbrecher, A. B. B. Mandal and S. P. Moulik, Phys. Chem. Chem. Phys., 2017, Accepted Manuscript , DOI: 10.1039/C7CP06796H

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