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Surfactant–waterborne polymer interactions in coating applications
Published in David R. Karsa, Surfactants in Polymers, Coatings, Inks and Adhesives, 2020
The most studied polymer–surfactant system is polyethylene oxide (PEO) and sodium dodecyl sulfate (SDS) and typical sigmoidal-shaped isotherms have been obtained [26]. The CMC for SDS is ∼8 mM in the absence of electrolyte. The CAC for association with PEO is ∼4mM in water and – 1mM in 0.1M NaCl corresponding to ΔG° values of −1.7 and – 2.12kJ per mole of surfactant, respectively. Using eq. (7.1), Shirahama [26] found Hill’s coefficient z to have a value of 20 in the presence of 0.1 M NaCl, indicating that the process was highly cooperative. The SDS:PEO binding ratio was found to be 0.4, corresponding to ∼16 bound micelles per polymer chain. A similar value for the number of bound micelles was reported by Xia et al. [16], who also showed that the number increased with increasing electrolyte concentration. The increased number is due to a reduction in the electrostatic repulsions between the surfactant aggregates due to the presence of the electrolyte. SDS has also been shown to interact with polyethylene oxide–polypropylene oxide–polyethylene oxide triblock copolymers (PEO–PPO–PEO), which are commonly used to stabilise particulate dispersions [27]. These polymers have considerably more hydrophobic character than PEO alone, and this is reflected in the fact that for PEO133–PPO50–PEO133 the CAC in the presence of 0.1 mM NaCl is reduced to ∼0.26 mM SDS.
Characterization Techniques
Published in Chandan Das, Sujoy Bose, Advanced Ceramic Membranes and Applications, 2017
The structure of inhomogeneous (core-shell) nanoparticles can be studied with the SAXS technique. The internal structure of sodium dodecyl sulfate (SDS) micelles in water was determined by calculating the radial electron density profile. For example, SDS is a highly effective anionic surfactant used in many hygiene and cleaning products or drug carrier systems. In aqueous solution, SDS molecules self-assemble and form micelles: SAXS allows one to obtain the shape and size of such nanosized micelles and—due to its sensitivity to electron-density differences—to determine the internal (core-shell) structure. This is of great importance for understanding and controlling the role of surfactants in different materials (e.g., the stability of emulsions or the release rate of the active ingredient in drug carrier systems).
Surface Active and Fracture-Forming Substances (Soaps and Detergents, etc.)
Published in K.S. Birdi, Surface Chemistry and Geochemistry of Hydraulic Fracturing, 2016
The solubility of all ionic surfactants (both anionics, which are negatively charged, and cationics, which are positively charged) is low at low temperature but at a specific temperature the solubility suddenly increases (Figure 3.4). For instance, the solubility of SDS at 15°C is about 2 g/L. This temperature is called the Krafft point (KP). The solubility of SDS increases drastically above its KP. A KP can be obtained by cooling an anionic surfactant solution (ca. 0.5 molar) from a high to a lower temperature until cloudiness suddenly appears. The KP is not very sharp in the case of impure surfactants, as generally found in industry.
Separation of rare earth elements from mixed-metal feedstocks by micelle enhanced ultrafiltration with sodium dodecyl sulfate
Published in Environmental Technology, 2022
Borte Kose-Mutlu, Heileen Hsu-Kim, Mark R. Wiesner
Effect of SDS concentration. The effectiveness of the MEUF process is mainly related to the surfactant concentration in the feed solution. SDS at concentrations ranging from below the CMC to higher than the CMC were evaluated. As shown in Figure 3, an increase of the SDS concentration resulted in increased SDS and REE rejections (i.e. recovery in the retentate) and decreased overall permeate flux Js for both kinds of UF membranes. For experiments with the UP150 membrane (150 kDa, ∼9 nm nominal pore size) (Figure 3(a)), the rejection was higher than 90% at SDS concentrations below the CMC. At these concentrations, micelles are not formed in the bulk suspension, but rather form at the membrane surface where concentrations increase due to concentration polarization. During the ultrafiltration process, rejected surfactant molecules deposit on the membrane surface in time and form a gel layer near the surface of the membrane. This gel layer, or micelle aggregation layer (MAL), binds REEs. The CMC of the SDS was determined to be 8.0 mM in this study and this result agrees with previous studies (see Fig. S3.a). Researchers previously studying MEUF also reported similar results on the rejection of cations using SDS with a concentration below the CMC [22,36].
Development of triblock polymersomes for catalase delivery based on quality by design environment
Published in Journal of Dispersion Science and Technology, 2021
Camila Areias Oliveira, Camila Forster, Patrícia Léo, Carlota Rangel-Yagui
Catalase is one of the proteins of the biological antioxidative system in the skin, where it removes hydrogen peroxide by converting it to water and oxygen. The activity assays (Figure 7) showed that catalase presents specific activity of 11035.86 ± 182.27 U/mg of protein, in agreement with the supplier’s information. To investigate the encapsulated enzyme activity, we disrupted the polymersomes with 1% SDS. Our results show that the simple addition of SDS to the pure catalase solution decreased activity by 25% (8196 ± 74 U/mg). SDS is an ionic surfactant well known to denature proteins by the combined effect of electrostatic interactions between positively-charged residues at the protein surface and negatively-charged head groups of the surfactant, and hydrophobic effect resulting from interactions between surfactant molecules tail and hydrophobic regions of the protein.[43] Nonetheless, a remaining activity of 23% (2594 ± 659 U/mg) of protein was detected after the encapsulation into polymersomes. As Findlay early reported, the human skin presents low concentrations of catalase, 60-153 U/g, yet enough to its important antioxidant function.[44]
Role of ammonium ion on the aggregation and adsorption properties of sodium dodecylsulfate
Published in Journal of Dispersion Science and Technology, 2018
We adapted to start our discussion with the well-studied aggregation behavior of SDS in water using surface tension (γ) and conductance measurements. The plots of variation of γ (layer A) and the specific conductance (κ) (layer B) of SDS in water are shown in Figure 1. It is well known that the γ isotherm for SDS exhibits a minimum and then constancy is reached, which has been taken as the cmc. The cmc of SDS in water has been found to be 8.3 mM, which is in good agreement with the reported value.[6] Likewise, the plot of specific conductance shows the slope change during micelle formation (Figure 1B) and the cmc values obtained from these two methods are in good agreement. As expected, no break in the conductance profile is obtained in the region where the minimum occurs in the γ isotherm because the impurity dodecanol is not expected to alter the conductance profile of SDS.