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Self-Assembly and Thermodynamic Properties of Dodecyldimethylethylammonium Bromide in Ethylene Glycol or Ethylene Glycol Oligomers and Water Mixed Solutions

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journal contribution
posted on 09.09.2019, 19:33 by Sha Li, HongCui Bao, Qian Zhang, Min Liu, Dezhi Sun, Jie Liu
The self-assembly behavior of dodecyldimethylethylammonium bromide (DEDAB) in mixed solvent media of ethylene glycol (EG)/water, polyethylene glycol 200 (PEG 200)/water, or polyethylene glycol 400 (PEG 400)/water at different temperatures was studied via conductivity and isothermal titration microcalorimetry (ITC) methods. The results showed that the three systems generated traditional or swollen surfactant micelles with the addition of EG or PEG oligomers. The critical micelle concentration (cmc) of DEDAB increased with the increasing cosolvent amount in mixed solvent, chain length, or temperature. The decrease in the dielectric constant of the solvent and “structure-breaking effect” of the cosolvent were not conducive to the micellization of the surfactant. Regarding thermodynamics, Gibbs energy of micellization (ΔGmo) changes more positively in mixed solvent than pure water. According to the values of ΔHmo and −TΔSmo, micelle formation of the three systems was driven entropically as well as enthalpically within the studied temperature scope and solvent composition. A comparison of chain length of the cosolvents was conducted, showing that the effect of temperature and cosolvent amount on mixed aqueous solution on cmc and thermodynamic parameters was crucial.

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