Tensiometry and FTIR study of the synergy in mixed SDS:DDAO surfactant solutions at varying pH

Tyagi, Gunjan; Seddon, Dale; Khodaparast, Sepideh; Sharratt, William N.; Robles, Eric S. J.; Cabral, João T.

doi:10.1016/j.colsurfa.2021.126414

Cited by 27 publications

(61 citation statements)

References 55 publications

(90 reference statements)

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“…The CMC and pH values of mixed SDS–DDAO solutions, as a function of surfactant molar ratio, are reported in Figure 2 a,b, respectively. The CMC decreases for all ratios, relative to the pure surfactant solutions, with a minimum value at a 1:1 stoichiometry (data previously reported in ref ( 23 )). The pH of the mixed solutions increases from neutral values of the pure surfactants to alkaline values (>7), indicating protonation of the DDAO and a reduction of free H + ions, and reaches a maximum at 9.5 for equimolar surfactant ratios.…”

Section: Resultssupporting

confidence: 82%

“… (a) CMC for SDS–DDAO mixtures measured at floating by pendant drop tensiometry. 23 The horizontal green line corresponds to 0.136 mM, below CMC at all ratios. (b) Solution pH of SDS–DDAO mixtures at 25 °C for three total surfactant concentrations above and below CMC.…”

Section: Resultsmentioning

confidence: 99%

“…The total scattering profiles of mixed surfactant series I are shown in Figure 3 d. For this series, all compositions are expected to be above the CMC of the solution, given the DDAO concentration is fixed at a value above the CMC of DDAO in solution. 23 The SANS profiles of solutions with SDS concentrations ≪ DDAO concentrations (SD1–4) appear characteristic of non-ionic, dilute micelles. However, as the concentration of SDS increases and becomes comparable to DDAO (∼mM), as seen in samples SD5–6, the intensity of the mid- Q region peak increases and is characteristic of charged micelle structure factor.…”

Section: Resultsmentioning

confidence: 99%

“…The role of pH is particularly relevant for such systems, as the protonation state of the amphotheric surfactant is non-trivially influenced by the presence of the anionic surfactant. As such, solution pH varies with concentration and stoichiometry, 23 in turn affecting the solution structures and the delicate stability of the mixture. In most practical applications, this pH “self-regulation” is impacted by chemical environments with distinct pH that perturb the solution structures and equilibrium, potentially causing precipitation and thus performance loss.…”

Section: Introductionmentioning

confidence: 99%

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Solution Structures of Anionic–Amphoteric Surfactant Mixtures near the Two-Phase Region at Fixed pH

et al. 2022

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We examine the solution structures in a mixed surfactant system of sodium dodecyl sulfate (SDS) and N , N -dimethyldodecylamine N -oxide (DDAO) in water, on both sides of the two-phase boundary, employing dynamic light scattering, small-angle neutron scattering, and Fourier transform infrared spectroscopy. The precipitate phase boundary was accessed by lowering pH to 8, from its floating pH 9.5 value, and was experimentally approached from the monomeric and micellar regions in three ways: at fixed DDAO or SDS concentrations and at a fixed (70:30) SDS:DDAO molar ratio. We characterize the size, shape, and interactions of micelles, which elongate approaching the boundary, leading to the formation of disk-like aggregates within the biphasic region, coexisting with micelles and monomers. Our data, from both monomeric and micellar solutions, indicate that the two phase structures formed are largely pathway-independent, with dimensions influenced by both pH and mixed surfactant composition. Precipitation occurs at intermediate stoichiometries with a similar SDS:DDAO ratio, whereas asymmetric stoichiometries form a re-entrant transition, returning to the mixed micelle phase. Overall, our findings demonstrate the effect of stoichiometry and solution pH on the synergistic interaction of mixed surfactants and their impact on phase equilibrium and associated micellar and two-phase structures.

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Section: Resultssupporting

confidence: 82%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Solution Structures of Anionic–Amphoteric Surfactant Mixtures near the Two-Phase Region at Fixed pH

et al. 2022

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“…Mixed surfactants have attracted a great deal of attention from researchers in various fields, including flotation, oil recovery, drug delivery, daily cosmetics, textiles, and pesticide emulsifiers [ 1 , 2 , 3 , 4 , 5 , 6 ]. Synergistic behavior between two different surfactants results in lower critical micelle concentration (CMC), lower interfacial tension, more stable micelles, and higher solubilization capacity [ 7 , 8 ], which means the combination of surfactants can compensate for each other [ 9 ]. The faster formation of micelles in the mixture reduces the dose of surfactants and their damage to the ecological environment.…”

Section: Introductionmentioning

confidence: 99%

Self-Assembly of NaOL-DDA Mixtures in Aqueous Solution: A Molecular Dynamics Simulation Study

Wang

Liu

et al. 2021

Molecules

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The self-assembly behaviors of sodium oleate (NaOL), dodecylamine (DDA), and their mixtures in aqueous solution were systematically investigated by large-scale molecular dynamics simulations, respectively. The interaction mechanisms between the surfactants, as well as the surfactants and solvent, were revealed via the radial distribution function (RDF), cluster size, solvent-accessible surface area (SASA), hydrogen bond, and non-bond interaction energy. Results showed that the molecules more easily formed aggregates in mixed systems compared to pure systems, indicating higher surface activity. The SASA values of DDA and NaOL decreased significantly after mixing, indicating a tighter aggregation of the mixed surfactants. The RDF results indicated that DDA and NaOL strongly interacted with each other, especially in the mixed system with a 1:1 molar ratio. Compared to van der Waals interactions, electrostatic interactions between the surfactant molecules were the main contributors to the improved aggregation in the mixed systems. Besides, hydrogen bonds were found between NaOL and DDA in the mixed systems. Therefore, the aggregates in the mixed systems were much more compact in comparison with pure systems, which contributed to the reduction of the repulsive force between same molecules. These findings indicated that the mixed NaOL/DDA surfactants had a great potential in application of mineral flotation.

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Fourier transform infrared spectroscopy in surfactant science: A personal view

Scheuing

2022

J Surfact & Detergents

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The overall goal of this review paper on Fourier transform infrared spectroscopy (FT‐IR) is to provide non‐specialists and spectroscopists alike a motivational introduction to how this technique may be used to obtain unique structural information on a wide range of surfactant‐based systems. Two main topics are addressed—The structures of surfactant aggregates in solution and the interactions of surfactants in solution with solid surfaces. Infrared spectra can yield insights into the interactions of surfactants in mixed micelles as well as in microemulsions. The structures of adsorbed surfactant layers and their kinetics of formation may be elucidated from FT‐IR spectra obtained using attenuated total reflectance sampling techniques. Insights into the detergency process of solid oily soils may also be obtained from the spectra of phases formed at the soil‐surfactant solution interface. Future work in applying FT‐IR to the development of the hydrophilic–lipophilic difference + net average curvature (HLD‐NAC) framework is proposed. Spectral interpretation principles examined in many examples, particularly regarding surfactant hydration and the loci of oil solubilization, could be used in the further development of HLD‐NAC through application to some microemulsion systems that have recently been reported.

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Tensiometry and FTIR study of the synergy in mixed SDS:DDAO surfactant solutions at varying pH

Cited by 27 publications

References 55 publications

Solution Structures of Anionic–Amphoteric Surfactant Mixtures near the Two-Phase Region at Fixed pH

Solution Structures of Anionic–Amphoteric Surfactant Mixtures near the Two-Phase Region at Fixed pH

Self-Assembly of NaOL-DDA Mixtures in Aqueous Solution: A Molecular Dynamics Simulation Study

Fourier transform infrared spectroscopy in surfactant science: A personal view

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