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Sodium Bromide Induced Micelle to Vesicle Transitions of Newly Synthesized Anionic Surface Active Ionic Liquids Based on Dodecylbenzenesulfonate

By K. Srinivasa Rao (739426), Praveen Singh Gehlot (1634176), Hariom Gupta (1464646), Markus Drechsler (1296345) and Arvind Kumar (227201)

Abstract

Dodecylbenezenesulfonate-based anionic surface active ionic liquids (DBS-ILs) paired with onium cations, <i>n</i>-butyltrimethylammonium ([N<sub>1114</sub>]), 1-butyl-3-methylimidazolium ([C<sub>4</sub>mim]), and <i>N</i>-butylpyridinium ([C<sub>4</sub>Py]) have been synthesized. DBS-ILs were found to be highly surface active having critical micelle concentration (CMC) lower than that of their conventional analogue sodium dodecylbenezenesulfonate ([Na]­[DBS]). The CMC values of DBS-ILs were determined from surface tension (ST) and isothermal titration calorimetry (ITC). DBS-ILs formed micelles predominantly in the aqueous medium, and unlike [Na]­DBS, the micelles of DBS-ILs could be transformed into vesicles with the addition of sodium bromide (NaBr). Micelle to vesicle transitions (MVTs) were evidenced from dynamic light scattering (DLS), turbidity, proton nuclear magnetic resonance (<sup>1</sup>H NMR), and cryo-TEM techniques. Thermodynamics of aggregation was investigated from ITC which indicated that the aggregation process is primarily driven by the entropy factor. The formation of a vesicle upon addition of NaBr has been accounted to the increased electrostatic interactions between the less hydrated sulfonate headgroup and the more populated bigger sized counterions along with the favored cation−π or π–π interactions between them as evidenced from 2D-NOESY NMR experiments. The stimuli-responsive morphological transitions in the self-assembly of the reported anionic surface active ionic liquids (SAILs) will be useful for encapsulation and delivery of active (bio)­molecules in the targeted biomedical applications

Topics: Biophysics, Biochemistry, Cell Biology, Physiology, Pharmacology, Environmental Sciences not elsewhere classified, Biological Sciences not elsewhere classified, Chemical Sciences not elsewhere classified, Physical Sciences not elsewhere classified, Ionic Liquids, sodium bromide, Vesicle Transitions, Sodium Bromide Induced Micelle, DLS, interaction, titration calorimetry, Na, vesicle transitions, onium cations, Synthesized Anionic Surface, MVT, surface tension, micelle concentration, entropy factor, NMR, ITC, ST, sulfonate headgroup, CMC values, aggregation process, NaBr
Year: 2015
DOI identifier: 10.1021/jp512805e.s001
OAI identifier: oai:figshare.com:article/2184904
Provided by: FigShare
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