Study of conductivity, contact angle and surface free energy of anionic (SDS, AOT) and cationic (CTAB) surfactants in water and isopropanol mixture

Effect of 2-Propanol on surface properties and wetting behavior of surfactants on the glass surface

This study investigates the effects of 2-Propanol (2-PrOH) on the surface and wetting properties of anionic - Sodium bis(2-ethyl hexyl) sulfosuccinate, also known as Aerosol AT (AOT), Sodium Dodecyl Sulfate (SDS) - and cationic - Cetylpyridinium Chloride (CPC) and Cetyltrimethylammonium Bromide (CTAB) surfactants on a glass surface. Key surface properties including surface tension(γ), critical micelle concentration (CMC), surface excess concentration ( Γ max ), and minimum surface area per molecule ( A min ), were determined in water and varying parts by volume (0.10, 0.20, and 0.30) 2-PrOH at 298.15 K. Additionally, Contact angle (CA), Adhesion tension ( A T ) and Work of Adhesion ( W A ) were analyzed to assess the impact of 2-PrOH on the wettability of the surfactant solutions. The results show that adding 2-PrOH significantly reduces the γ and CA, enhancing the wetting properties of all surfactants. Γ max decreases, while A min increases, indicating a more dispersed arrangement of surfactant molecules at the air/solution interface in the presence of 2-PrOH. This leads to improved spreading and adhesion on the glass surface, as demonstrated by increased A T and W A with increasing 2-PrOH parts by volume. The study concludes that 2-PrOH acts as an effective co-surfactant optimizing surfactant performance by lowering the γ and enhancing liquid/solid interactions, making these systems more effective in applications requiring strong wetting and adhesion. These findings provide valuable insights for designing surfactant formulations for industrial applications such as coatings, detergents, and surface treatments.

Exploration of the micellization behavior of sodium dodecyl sulfate in aqueous solution of gastric enzyme pepsin: Assessment of the consequences of sodium electrolytes and temperature

This study explores the interactions between pepsin and sodium dodecyl sulfate (SDS) using conductometric analysis and molecular docking to deepen our understanding of the role of pepsin. Conductometric studies were conducted to examine the micellization behavior of SDS with pepsin in aqueous solutions of various sodium electrolytes (NaBr, Na₂SO₄, Na₃PO₄, and CH₃COONa) at temperatures ranging from 300.55 K to 320.55 K in 5 K increments. The critical micelle concentration (CMC) of the SDS-pepsin system was influenced by pepsin concentration, electrolyte type, and temperature. Pepsin was found to inhibit SDS micellization, increasing the CMC, while electrolytes promoted micellization, decreasing the CMC. Thermodynamic parameters-Gibbs free energy (∆Gm0), enthalpy (∆Hm0), and entropy (∆Sm0)-were analyzed to identify the driving forces behind micellization. The negative ∆Gm0 indicated spontaneous aggregation, with ∆Hm0 and ∆Sm0 suggesting hydrophobic and electrostatic interactions. Molecular docking further confirmed these interactions, revealing binding between the hydrophobic tail of SDS and nonpolar binding pocket of pepsin at the interdomain cleft. These findings provide insights into surfactant-enzyme interactions, with potential applications in biochemistry, pharmacology, and food science.

Interaction of Remalan Brilliant Blue R dye with n-alkyltrimethylammonium chloride surfactants: conductometric and spectroscopic investigations

Micellization behaviour, thermodynamics and dye-surfactant interactions are the main topics of this investigation into the relationship between Remalan Brilliant Blue R (RBBR) dye and n-alkyltrimethylammonium chloride (C n TAC; n = 12, 14, 16 and 18) surfactants. Conductometric analysis revealed that the critical micelle concentration decreased with increasing alkyl chain length, suggesting that longer chains formed better micelles. Due to electrostatic interactions, spectrophotometric analyses revealed notable alterations in RBBR absorption following contact with C n TAC. Benesi-Hildebrand and Scott equations were used to compute the binding constant (K b), which increased with chain length, indicating stronger dye-micelle interactions. The spontaneous interactions between RBBR and micelles were confirmed by thermodynamic analysis, which showed negative Gibbs free energy values (ΔG). The stability of dye-micelle complexes is attributed to hydrophobic forces, as seen by the greater negative ΔG that was produced by longer alkyl chains. Interestingly, increased surfactant concentrations changed equilibrium and decreased dye adsorption by breaking up pre-formed RBBR-C n TAC complexes. These results highlight how important the length of the alkyl chain is for micelle formation, thermodynamic parameters and dye-surfactant interactions. As the length of the chain grew, the sequence of RBBR binding strength was found to be C12TAC < C14TAC < C16TAC < C18TAC.

Polymerized whey protein-SDS interactions at their high concentrations

Protein-surfactant interactions have been an ongoing topic of interest for many decades. Applications involving complexes of proteins and surfactants are relevant in food, pharmaceuticals, hygiene, molecular characterization, and other fields. In this study, the interactions of polymerized whey proteins (PWP) and sodium dodecyl sulfate (SDS) at high concentrations are investigated. Different characterization techniques are used, including electrical conductivity, turbidity, isothermal titration calorimetry, dynamic light scattering, dilute solution viscometry, rheology, and surface hydrophobicity to elucidate information on the modes and extent of interactions. Results indicate that PWP-SDS interactions produce highly extended, worm like micelles, with SDS decorating PWP chains and covering non-polar residues. PWP can host SDS up to quite high surfactant to protein ratios (SPR), producing solutions that are highly viscous with shear thickening properties, yet with no networking or gelation. Interestingly, dilution of high viscosity PWP-SDS solutions leads to even smaller size of PWP-SDS molecular complex as compared with PWP without SDS. The current study extends the vision of protein surfactant interactions by examining concentration range beyond that found in literature. The results reveal insights that can help expand studies on other systems and find applications in various fields including coatings, cosmetics, food ingredients, drug transport, and disease treatment.

Association in Like-Charged Surfactant-Nanoparticle Systems: Interfacial and Bulk Effects

The association of similarly charged surfactant molecules and nanoparticles in an aqueous solution remains unresolved, and the understandings reported in the literature are conflicting. To address this issue, we undertake a fundamental study to investigate bulk and interfacial phenomena in binary mixtures of (i) positively charged nanoparticles and cationic surfactants and (ii) negatively charged nanoparticles and anionic surfactants. We find that the surfactant molecules adsorb on the surface of the nanoparticle despite similar charge, leading to supercharging of particles and simultaneously driving more surfactant molecules to the air-dispersion interface. Hence, the properties of the dispersed species, such as the size and zeta potential, and the interfacial properties, such as the surface tension and surface excess concentration, change significantly. This effect is more pronounced at a low surfactant concentration and is observed irrespective of the size of nanoparticles and surfactant-particle combination. Further, we elucidate the important role of electrostatic interactions in the surfactant-particle complexation process by varying the pH of the dispersions. Contrary to changes in the properties of the dispersed species and interface, the presence of particles does not appreciably change the bulk property, such as the critical micelle concentration.

Dioctyl sodium sulfosuccinate surfactant self-assembly dependency of solvent hydrophilicity: a modelling study

The self-assembly of dioctyl sodium sulfosuccinate (AOT) model surfactant in solvent environments of differing polarity is examined by means of dissipative particle dynamics (DPD) bead model parametrized against Hildebrand solubility parameters from atomistic molecular dynamics (MD) simulations. The model predicts that in hydrophobic solvents (e.g. dodecane) the surfactant forms small (Nagg ∼ 8) reverse micellar aggregates, while in a solvent corresponding to water lamellar assembly takes place, in good agreement with literature structural parameters. Interestingly, solvents of intermediate polarity lead to formation of large, internally structured aggregates. In these, the surfactant headgroups cluster within the aggregate, surrounded by a continuous phase formed by the hydrocarbon tails. We show that the partitioning of the headgroups between the aggregate surface layer and the inner clustered phase depends primarily on solvent polarity, and can be controlled by the solvent, but also system composition. Finally, we compare the DPD assembly response to simplified effective interaction potentials derived at dilute concentration limit for the interactions. The comparison reveals that the simplified effective potential descriptions provide good level of insight on the assembly morphologies, despite drastic, isotropic interactions simplification involved.

Development of Genistein Drug Delivery Systems Based on Bacterial Nanocellulose for Potential Colorectal Cancer Chemoprevention: Effect of Nanocellulose Surface Modification on Genistein Adsorption

Genistein is an isoflavone with antioxidant, anti-inflammatory, and anticancer properties. That said, its use in the industry is limited by its low solubility in aqueous systems. In this work, bacterial nanocellulose (BNC) and BNC modified with cetyltrimethylammonium (BNC-CTAB) were evaluated as genistein-encapsulating materials for their controlled release in cancer chemoprevention. Thin films were obtained and characterized by contact angle, AFM, TEM, UV–Vis spectroscopy FTIR, and TGA techniques to verify surface modification and genistein encapsulation. The results show a decrease in hydrophilization degree and an increase in diameter after BNC modification. Furthermore, the affinity of genistein with the encapsulating materials was determined in the context of monolayer and multilayer isotherms, thermodynamic parameters and adsorption kinetics. Spontaneous, endothermic and reversible adsorption processes were found for BNC-GEN and BNC-CTAB-GEN. After two hours, the maximum adsorption capacity corresponded to 4.59 mg GEN∙g⁻¹ BNC and 6.10 mg GEN∙g⁻¹ BNC-CTAB; the latter was a more stable system. Additionally, in vitro release assays performed with simulated gastrointestinal fluids indicated controlled and continuous desorption in gastric and colon fluids, with a release of around 5% and 85%, respectively, for either system. Finally, the IC50 tests made it possible to determine the amounts of films required to achieve therapeutic concentrations for SW480 and SW620 cell lines.

Preparation and evaluation of humic acid-based composite dust suppressant for coal storage and transportation

To mitigate environmental pollution caused by the escape of dust during coal storage and transportation, humic acid (HA) and grafted acrylamide (AM) were used as raw materials to prepare a composite dust suppressant suitable for coal storage and transportation. Single-factor experiments were used to explore the optimal synthesis conditions of the dust suppressant, and the microstructure of the product was studied using Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H-NMR), scanning electron microscopy (SEM), and other methods. The wetting effect of the dust suppressant on coal was also investigated by way of molecular dynamics (MD) simulations. The experimental results showed that the dust suppressant had good wind erosion resistance (wind erosion rate 10.2%), shock resistance (loss rate 3.63%), and anti-evaporation performance, while the MD simulation and permeability analysis results showed that the dust suppressant had an excellent wetting effect on the coal surface. SEM images revealed that the dust suppressant can fill the gaps between coal dust particles and bond them together to form a consolidated layer, thereby effectively inhibiting the escape of dust sources during coal storage and transportation.

Healable, Adhesive, and Conductive Nanocomposite Hydrogels with Ultrastretchability for Flexible Sensors

In recent years, conductive hydrogels have generated tremendous attention in biomedicals and bioelectronics fields due to their excellent physiochemical properties. In this study, a physically cross-linked conducting hydrogel has been designed in combination with cellulose nanocrystalline (CNC), polyacrylic acid (PAA) chains, laurel methacrylate, and sodium dodecyl sulfate. The obtained result shows that the hydrogel prepared is ultrastretchable, mechanically robust, transparent, biocompatible, conductive, and self-healing. The mechanical property of the prepared hydrogel is optimized through variation of the CNC content. The optimal hydrogel (CNC-1/PAA) exhibits an impressive mechanics, including high stretchability (∼1800%) and compressibility, good elasticity, and fatigue resistance. Furthermore, the conductivity of the hydrogel enables tensile strain- and pressure-sensing capabilities. The CNC/PAA-based flexible sensors are successfully designed, which shows high sensitivity, fast response (290 ms), and excellent cycle stability as well as the pressure sensing capability. As a result, the designed hydrogel has the ability to sense and detect diverse human motion, including elbow/finger/wrist bending and speaking, which demonstrates that the designed self-healing conductive hydrogels have significant potential for applications in flexible electronics.

Impacts of polyols and temperature on the micellization, interaction and thermodynamics behavior of the mixture of tetradecyltrimethylammonium bromide and polyvinyl alcohol

Herein, the aggregation manner of the mixture of polyvinyl alcohol (PVA) and tetradecyltrimethylammonium bromide (TTAB) was performed in polyols (glucose, maltose and galactose) media over 300.55–320.55 K temperatures range with 5 K interval through conductivity measurement method. The micelle formation of TTAB + PVA mixture was identified by the assessment of critical micelle concentration (CMC) from the plots of specific conductivity (κ) versus TTAB concentration. The degree of micelle ionization (α), the extent of bound counter ions (β) as well as thermodynamic properties ( Δ G m 0 ${\Delta}{G}_{m}^{0}$ , Δ H m 0 ${\Delta}{H}_{m}^{0}$ and Δ S m 0 ${\Delta}{S}_{m}^{0}$ ) of TTAB + PVA systems have been estimated. The CMC values reveal that the micelle formation of TTAB + PVA mixture experience an enhancement in the manifestation of polyols. The values of free energy of micellization ( Δ G m 0 ${\Delta}{G}_{m}^{0}$ ) are negative for the TTAB + PVA system in aqueous polyols media, suggesting a spontaneous aggregation phenomenon. The Δ H m 0 ${\Delta}{H}_{m}^{0}$ and Δ S m 0 ${\Delta}{S}_{m}^{0}$ values of TTAB + PVA systems direct that the PVA molecule interacts with TTAB through the exothermic, ion-dipole, and hydrophobic interactions. The thermodynamic properties of transfer were also determined for the move of TTAB + PVA mixture from H2O to water + polyols mixed solvents. The values of compensation temperature (T c) and intrinsic enthalpy gain ( Δ H m 0 , ∗ ${\Delta}{H}_{m}^{0,\ast }$ ) were evaluated and discussed for the studied system.

Contrasting effect of 1-butanol and 1,4-butanediol on the triggered micellar self-assemblies of C16-type cationic surfactants

The self-assembly in aqueous solutions of three quaternary salt-based C₁₆-type cationic surfactants with different polar head groups and identical carbon alkyl chain viz., cetylpyridinium bromide (CPB), cetyltrimethylammonium tosylate (CTAT), and cetyltriphenylphosphonium bromide (CTPPB) in the presence of 1-butanol (BuOH) and 1,4-butanediol (BTD) was investigated using tensiometry, 2D-nuclear Overhauser enhancement spectroscopy (2D-NOESY) and small angle neutron scattering (SANS) techniques. The adsorption parameters and micellar characteristics evaluated at 303.15 K distinctly showed that BuOH promotes the mixed micelle formation while BTD interfered with the micellization phenomenon. The SANS data fitted using an ellipsoid (as derived by Hayter and Penfold using the Ornstein-Zernike equation and the mean spherical approximation) and wormlike micellar models offered an insight into the micelle size/shape and aggregation number (N_agg) in the examined systems. The evaluated descriptors presented a clear indication of the morphology transition in cationic micelles as induced by the addition of the two alcohols. We also offer an investigation into the acceptable molecular interactions governing the differences in micelle morphologies, using the non-invasive 2D-NOESY technique and molecular modeling. The experimental observations elucidated from computational simulation add novelty to this work. Giving an account to the structural complexity in the three cationic surfactants, the molecular dynamics (MD) simulation was performed for CPB micelles in an aqueous solution of alcohols that highlighted the micelle solvation and structural transition, which is further complemented in terms of critical packing parameter (PP) for the examined systems.

Properties of some nonionic fluorocarbon surfactants and their mixtures with hydrocarbon ones

The adsorption of Zonyl FSN-100 (FSN100, having an average 14 oxyethylene units and 6 -CF₂ groups) and Zonyl FSO-100 (FSO100, having an average 10 oxyethylene units and 5 -CF₂ groups) as well as of their mixtures with p-(1,1,3,3-tetramethylbutyl) phenoxypoly(ethylene glycols) having 10, 16 and 8 oxyethylene groups in molecule (TX100, TX165, TX114) and cetyltrimethylammonium bromide (CTAB) at the solution-air and polytetrafluoroethylene (PTFE)-solution and polymethyl methacrylate (PMMA)-solution interfaces as well as the composition of the surface mixed layer was discussed based on the literature data. The adsorption properties of nonionic fluorocarbon surfactants were compared to those of the classical ones on the basis of the Gibbs standard free energy of adsorption determined by different ways and the intermolecular interactions of the surfactant molecules through the water phase. The synergetic effect in the reduction of the water surface tension by the mixture of fluorocarbon and classical nonionic surfactant was shown and explained by the comparison of the composition of the mixed surface layer to those in the bulk phase. The composition of the mixed fluorocarbon and classical surfactant layer at the solution-air interface was compared to that formed at the PTFE-solution and PMMA-solution interfaces. The changes of the surface tension of the aqueous solution of the fluorocarbon surfactants and their mixtures with classical hydrocarbon ones and their adsorption were analyzed taking into account the PTFE and PMMA surface wettability. This analysis was also based on the components and parameters of the head and tail of the surfactants surface tension as well as those of PTFE and PMMA. Apart from adsorption and wetting properties the aggregation of the fluorocarbon surfactants and their mixtures was discussed. A specific attention was paid to the possibility of two CMC values in the case of nonionic fluorocarbon surfactants as well as the synergism in CMC of mixtures of nonionic fluorocarbon and hydrocarbon surfactants.

Aggregation behavior and thermodynamic properties of the mixture of sodium carboxymethyl cellulose and cetyltrimethylammonium bromide in numerous temperatures and mixed solvents

Interaction of sodium carboxymethylcellulose (SCMC) with cetyltrimethylammonium bromide (CTAB; cationic in nature) in H2O and additives (alcohols and diols) media has been investigated using conductivity technique. The micellar parameters such as critical micelle concentration (cmc), fraction of counter ion binding (β), thermodynamic parameters, transfer properties, and enthalpy-entropy compensation parameters of CTAB + SCMC mixture have been assessed in water and aq. alcohols/diols media. One cmc value was achieved for CTAB + SCMC mixtures in the entire circumstances and the attendance of SCMC disfavors the CTAB micellization. The cmc values were obtained to be greater in alcohols and diols media compared to H2O medium. The cmc values also exhibit a dependency on the solvent composition and temperature variation. In all the cases, the ΔG 0 m values were achieved to be negative which signifying the spontaneous formation of micelles while the extent of spontaneity is decreased in alcohols and diols media. Both the ΔH 0 m and ΔS 0 m reveal that hydrophobic, ion-dipole as well as electrostatic interactions are the proposed binding forces between CTAB and SCMC. The compensation parameters (ΔH 0* m and T c ) are in decent agreement with the biological fluid.