Investigation of Surfactant-Polymer Interactions Using Rheology and Surface Tension Measurements

Microemulsion gel systems: Formulation, stability studies, biopolymer interactions, and functionality in food product development

Microemulsion gels (MGs) are nanostructured systems created by the addition of thickening agents/biopolymers to a microemulsion's aqueous or oily phases, offering benefits like improved solubilization, enhanced stability, high encapsulation efficiency, and sustained release with versatile applications in food, pharmaceuticals, and cosmetology. MGs are intricate systems with thermodynamic robustness and controllable rheological characteristics crucial for obtaining high structural integrity and achieving innovative results regarding food product development in diverse areas of food, including colloidal carriers, food packaging, active compound delivery, antimicrobial vectors, and production of biopolymer nanoparticles. Therefore, a comprehensive analysis, hence understanding about MG systems, is needed to identify trends and gaps, helping researchers to identify promising areas for innovation and providing direction for future research. This review offers a comprehensive analysis of MG systems, their characteristics, formulation, formation mechanisms, design approaches, digestion dynamics, and rheological properties. MGs excel in solubilizing hydrophilic and lipophilic bioactives due to their enhanced viscosity and interconnected droplet network within the gel matrix. Despite their advantages, challenges, such as formulation complexity, require further understanding. This article also explores innovative biopolymers, characterization, and extensive applications, while addressing case studies, and emerging trends leveraging the potential of MG systems for enhancing food stability, functionality, and nutritional value.

Steady Shear Rheology and Surface Activity of Polymer-Surfactant Mixtures

Understanding the interactions between polymers and surfactants is critical for designing advanced fluid systems used in applications such as enhanced oil recovery, drilling, and chemical processing. This study examines the effects of five surfactants: two anionic (Stepanol WA-100 and Stepwet DF-95), one cationic (HTAB), one zwitterionic (Amphosol CG), and one non-ionic (Alfonic 1412-3 Ethoxylate), on the steady shear rheology and surface activity of two polymers, namely cationic hydroxyethyl cellulose based polymer (LR-400) and anionic polyacrylamide based polymer (Praestol 2540TR). The polymer-surfactant solutions behave as shear-thinning fluids and follow the power-law model. Anionic surfactants exhibit a strong effect on the rheology of cationic polymer LR-400 solution. The consistency index rises sharply with the increase in surfactant concentration. Also, the solutions become highly shear-thinning with the increase in surfactant concentration. The effects of other surfactants on the rheology of cationic polymer solution are small to modest. None of the surfactants investigated exhibit a strong influence on the rheology of anionic polymer Praestol 2540TR. Only weak to modest effects of surfactants are observed on the rheology of anionic polymers. The surface tension of the polymer-surfactant solution decreases with the increase in surfactant concentration. Zwitterionic surfactant Amphosol CG is found to be most effective in reducing the surface tension at a given concentration in ppm. This surfactant also raises the electrical conductivity of the solution to the largest extent. From the changes in slope of surface tension versus surfactant concentration plots, the approximate values of critical aggregation concentration (CAC) and polymer saturation point (PSP) are estimated.

Influence of Added Cellulose Nanocrystals on the Rheology of Polymers

The interactions between cellulose nanocrystals and six different polymers (three anionic, two non-ionic, and one cationic) were investigated using rheological measurements of aqueous solutions of nanocrystals and polymers. The experimental viscosity data could be described adequately by a power-law model. The variations in power-law parameters (consistency index and flow behavior index) with concentrations of nanocrystals and polymers were determined for different combinations of nanocrystals and polymers. The interactions between nanocrystals and the following polymers: anionic sodium carboxymethyl cellulose and non-ionic guar gum, were found to be strong in that the consistency index increased substantially with the addition of nanocrystals to polymer solutions. The interaction between nanocrystals and non-ionic polymer polyethylene oxide was moderate. Depending on the concentrations of nanocrystals and polymer, the consistency index both increased and decreased upon the addition of nanocrystals to polymer solution. The interactions between nanocrystals and the following polymers: anionic xanthan gum, anionic polyacrylamide, and cationic quaternary ammonium salt of hydroxyethyl cellulose, were found to be weak. The changes in rheological properties with nanocrystal addition to these polymer solutions were found to be small or negligible.

The Effect of the Microstructure and Viscosity of Modified Bitumen on the Strength of Asphalt Concrete

The purpose of these studies was to establish the influence of the microstructural and rheological characteristics of modified bitumen compositions on the strength indicators of asphalt concrete. The effect of additives concentration on the rheological characteristics and microstructure of binary "bitumen-surfactant", "bitumen-AG-4I", and ternary "bitumen-AG-4I-AG-4I" systems has been studied. To assess the effect of bitumen dispersion on the physical and mechanical characteristics of modified asphalt concrete samples, the compressive strength value was determined. The following chemicals have been used as additives: the original product AS-1, industrial additive AMDOR-10, and used sealant AG-4I, a product based on polyisobutylene and petroleum oils. At an increased content of AG-4I (C ≥ 1.0 g/dm3) in ternary systems, the contribution of the emerging intermolecular polyisobutylene network to the development of structuring processes increases while the viscous effect of the surfactant AS-1 decreases. It has been established that the minimum size of bee-like bitumen structures (1.66 µm) is recorded with the joint presence of additives in the bitumen, AS-1 at a level of 1.0 g/dm3 and AG-4I at a level of 1.0 g/dm3. Under the same concentration regimes of the ternary bitumen composition, the maximum increase in compressive strength RD was achieved with the smallest size of bee-like structures of modified bitumen.

Remediation of multilayer soils contaminated by heavy chlorinated solvents using biopolymer-surfactant mixtures: Two-dimensional flow experiments and simulations

To assess the efficiency of remediating dense non-aqueous phase liquids (DNAPLs), here heavy chlorinated solvents, through injection of xanthan solutions with or without surfactant (sodium dodecylbenzenesulfonate: SDBS), we conducted a comprehensive investigation involving rheological measurements, column (1D) and two-dimensional (2D) sandbox experiments, as well as numerical simulations on two-layers sand packs. Sand packs with grain sizes of 0.2-0.3 mm and 0.4-0.6 mm, chosen to represent the low and high permeable soil layers respectively, were selected to be representative of real polluted field. The rheological analysis of xanthan solutions showed that the addition of SDBS to the solution reduced its viscosity due to repulsive electrostatic forces and hydrophobic interactions between the molecules while preserving its shear-thinning behavior. Results of two-phase flow experiments depicted that adding SDBS to the polymer solution led to a reduced differential pressure along the soil and improvements of the DNAPL recovery factor of approximately 0.15 and 0.07 in 1D homogeneous and 2D layered systems, respectively. 2D experiments revealed that the displacement of DNAPL in multilayer zones was affected by permeability difference and density contrast in a heterogeneous soil. Simulation of multiphase flow in a multilayered system was performed by incorporating non-Newtonian properties and coupling the continuity equation with generalized Darcy's law. The results of modeling and experiments are very consistent. Numerical simulations showed that for an unconfined soil, the recovery of DNAPL by injection of xanthan solution can be reduced for more than 50%. In a large 2D experimental system, the combination of injecting xanthan with blocking the contaminated zone led to a promising remediation of DNAPL-contaminated layered zones, with a recovery of 0.87.

Phycoremediation potential and agar yield of red macroalgae (Gracilaria corticata) against HEDP (hydroxyethylidene diphosphonic acid) and CAPB (cocoamidopropyl betaine) detergents and the heavy metal pollutants

The discharge of raw industrial, agricultural, and domestic wastes leads to an increase in heavy metal (HM) burden and detergents in aquatic environs, which can have destructive effects on aquatic organisms. Agarophyte Gracilaria corticata, a major component of seaweed flora of the southern coast of Iran (Bushehr) that contains agar and red pigments, is one of the economically valuable red marine algae. Agar is one of the important polysaccharides with high economic value, widely used in pharmaceutical, medicinal, and cosmetic product manufacturing industries. The aim of this work was to investigate the effect of 5 HMs and two common surfactants in household and industrial detergents on the agar yield, appearance color, and the red algae's phycoremediation potential against HMs. The metal ions were Zn(II), Cu(II), Ni(II), Mn(II), and Cr(VI), and the surfactants were HEDP and CAPB. The analysis results of samples cultured for 60 days in seawater and polluted environments showed that G. corticata can accumulate copper and nickel. In the presence of detergents without HMs, the amount of extracted agar significantly increased compared to the control sample with no change in algae color. But with increasing concentration of HMs, the amount of agar in seaweed samples decreased significantly, and the algae discolored from red to dark green or yellowish-green color (signs of death in the algae). These results show that increasing of HM pollution and detergents can lead to toxicological effects and reduce the species diversity of red seaweeds in the future.

Viscosity of Sodium Polystyrenesulfonate with Cetyltrimethylammonium Bromide in the Mixture of Methanol and Water

Viscosity of cetyltrimethylammonium bromide (CTAB) in the presence of sodium polystyrene sulfonate (NaPSS) in methanol-water mixed solvent media has been reported at 308.15 K. The results have been analyzed on the basis of a simple model based on the scaling theory of the viscosity of polyelectrolyte solutions put forward by Plucktaveesak et al. (J. Phys. Chem. B, 2003, 107, 8166-8171). The specific viscosity data obtained here for the CTAB-NaPSS couple in mixed solvent media agree very well with the predictions of the above model. It has been established that the fraction of free counterions of the polyelectrolyte can be conveniently recovered in these complex fluids.

Interactions between Ionic Cellulose Derivatives Recycled from Textile Wastes and Surfactants: Interfacial, Aggregation and Wettability Studies

Interactions between polymers (P) and surfactants (S) in aqueous solution lead to interfacial and aggregation phenomena that are not only of great interest in physical chemistry but also important for many industrial applications, such as the development of detergents and fabric softeners. Here, we synthesized two ionic derivatives-sodium carboxymethylcellulose (NaCMC) and quaternized cellulose (QC)-from cellulose recycled from textile wastes and then explored the interactions of these polymers with assorted surfactants-cationic (CTAB, gemini), anionic (SDS, SDBS) and nonionic (TX-100)-commonly used in the textile industry. We obtained surface tension curves of the P/S mixtures by fixing the polymer concentration and then increasing the surfactant concentration. In mixtures where polymer and surfactant are oppositely charged (P^-/S⁺ and P⁺/S^-), a strong association is observed, and from the surface tension curves, we determined the critical aggregation concentration (cac) and critical micelle concentration in the presence of polymer (cmc^p). For mixtures of similar charge (P⁺/S⁺ and P^-/S^-), virtually no interactions are observed, with the notable exception of the QC/CTAB system, which is much more surface active than the neat CTAB. We further investigated the effect of oppositely charged P/S mixtures on hydrophilicity by measuring the contact angles of aqueous droplets on a hydrophobic textile substrate. Significantly, both P^-/S⁺ and P⁺/S^- systems greatly enhance the hydrophilicity of the substrate at much lower surfactant concentrations than the surfactant alone (in particular in the QC/SDBS and QC/SDS systems).

Impact of Novel Teflon-DCA Nanogel Matrix on Cellular Bioactivity

The biocompatibility and effects on cells' bioactivity of developed pharmaceuticals are crucial properties, required to permit their safe delivery. Nanogel matrices offer a promising role in emerging pharmaceutics; however, it is crucial that they and their excipients do not demonstrate detrimental effects on the cells to which they interact. This study investigated the use of Teflon and the secondary bile acid deoxycholic acid in the formation of novel nanogel matrices. Each has properties which may be of benefit for the nanogels created and their use in the pharmaceutical industry. Rheological parameters and scanning electron microscopy studies were conducted. In order to assess the developed nanogels' impacts on cellular bioactivity, studies using Seahorse assays were conducted on three cell types, hepatic, muscle and pancreatic beta cells. Results demonstrated the addition of Teflon did not alter the morphological characteristics of resulting nanogels or the metabolic profiles of the cell lines. Interestingly, pancreatic beta cells highlighted the potential of Teflon to exert a protective profile from mitochondrial damage. Overall, the developed nanogels showed potentially promising profiles in certain studies conducted which may lead to future research.

Visualization of Polymer–Surfactant Interaction by Dual-Emissive Gold Nanocluster Labeling

Polymer-surfactant interaction decides the performance of corresponding complexes, making its rapid and intuitionistic visualization important for enhancing the performance of products and/or processing in related fields. In this study, the fluorescence visualization of the interaction between cationic hyperbranched polyethyleneimine and anionic sodium dodecyl sulfonate surfactant was realized by dual-emissive gold nanocluster labeling. The sensing mechanism was due to the interaction-induced polymer conformation change, which regulated the molecular structure and subsequent photoradiation process of the gold nanoclusters. All three inflection points of the interactions between the polymers and the surfactants were obtained by the change in fluorescence emission ratio of the designed dual-emissive gold nanoclusters. Moreover, these inflection points are verified by the hydrodynamic diameter and zeta potential measurements.

Effect of Ionic and Non-Ionic Surfactant on Bovine Serum Albumin Encapsulation and Biological Properties of Emulsion-Electrospun Fibers

Emulsion electrospinning is a method of modifying a fibers’ surface and functional properties by encapsulation of the bioactive molecules. In our studies, bovine serum albumin (BSA) played the role of the modifier, and to protect the protein during the electrospinning process, the W/O (water-in-oil) emulsions were prepared, consisting of polymer and micelles formed from BSA and anionic (sodium dodecyl sulfate–S) or nonionic (Tween 80–T) surfactant. It was found that the micelle size distribution was strongly dependent on the nature and the amount of the surfactant, indicating that a higher concentration of the surfactant results in a higher tendency to form smaller micelles (4–9 µm for S and 8–13 µm for T). The appearance of anionic surfactant micelles reduced the diameter of the fiber (100–700 nm) and the wettability of the nonwoven surface (up to 77°) compared to un-modified PCL polymer fibers (100–900 nm and 130°). The use of a non-ionic surfactant resulted in better loading efficiency of micelles with albumin (about 90%), lower wettability of the nonwoven fabric (about 25°) and the formation of larger fibers (100–1100 nm). X-ray photoelectron spectroscopy (XPS) was used to detect the presence of the protein, and UV-Vis spectrophotometry was used to determine the loading efficiency and the nature of the release. The results showed that the location of the micelles influenced the release profiles of the protein, and the materials modified with micelles with the nonionic surfactant showed no burst release. The release kinetics was characteristic of the zero-order release model compared to anionic surfactants. The selected surfactant concentrations did not adversely affect the biological properties of fibrous substrates, such as high viability and low cytotoxicity of RAW macrophages 264.7.

Elucidating the Impact of Surfactants on the Performance of Dissolving Microneedle Array Patches

The need for biocompatible polymers capable of dissolving in the skin while exhibiting reasonable mechanical features and delivery efficiency limits the range of materials that could be utilized in fabricating dissolving microneedle array patches (MAPs). The incorporation of additives, such as surfactants, during microneedle fabrication might be an alternative solution to overcome the limited range of materials used in fabricating dissolving MAPs. However, there is a lacuna in the knowledge on the effect of surfactants on the manufacture and performance of dissolving MAPs. The current study explores the role of surfactants in the manufacture and performance of dissolving MAPs fabricated from poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) loaded with the model drugs, ibuprofen sodium and itraconazole. Three nonionic surfactants, Lutrol F108, Pluronic F88, and Tween 80, in solutions at varying concentrations (0.5, 1.0, and 2.0% w/w) were loaded into these dissolving MAPs. It was discovered that all of the dissolving MAPs that incorporated surfactant displayed a lower reduction in the microneedle height (≈10%) relative to the control formulation (≈20%) when subjected to a compressive force of 32 N. In addition, the incorporation of surfactants in some instances enhanced the insertion profile of these polymeric MAPs when evaluated using ex vivo neonatal porcine skin. The incorporation of surfactant into ibuprofen sodium-loaded dissolving MAPs improved the insertion depth of MAPs from 400 μm down to 600 μm. However, such enhancement was not apparent when the MAPs were loaded with the model hydrophobic drug, itraconazole. Skin deposition studies highlighted that the incorporation of surfactant enhanced the delivery efficiency of both model drugs, ibuprofen sodium and itraconazole. The incorporation of surfactant enhanced the amount of ibuprofen sodium delivered from 60.61% up to ≈75% with a majority of the drug being delivered across the skin and into the receptor compartment. On the other hand, when surfactants were added into MAPs loaded with the model hydrophobic drug itraconazole, we observed enhancement in intradermal delivery efficiency from 20% up to 30%, although this did not improve the delivery of the drug across the skin. This work highlights that the addition of nonionic surfactant is an alternative formulation strategy worth exploring to improve the performance and delivery efficiency of dissolving MAPs.

Nano-Hydroxyapatite Gel and Its Effects on Remineralization of Artificial Carious Lesions

Introduction

Nano-hydroxyapatite gel (NHG) has never been investigated for enamel remineralization. This study evaluated the effects of two concentrations of NHG on remineralization of an artificial carious lesion in comparison with nano-HA toothpaste (NHT) and fluoride varnish (FV).

Materials and Methods

Carious lesions were prepared on 100 enamel samples and divided into 5 groups: FV, NHT, 20% NHG, and 30% NHG. One untreated (NT) group was left as control. The hardness of the surface was evaluated before, during, and after remineralization. Microhardness at various phases and the percent recovery of hardness (%HR) were determined and analyzed with ANOVA. Polarized-light micrographs (PLM) were evaluated for depth of the carious lesion.

Results

Significantly different remineralization capability was indicated for tested agents (p < 0.05). NHT was significantly capable of remineralization greater than NHG, FV, and NT (p < 0.05). No noticeable difference in %HR between 20% NHG and 30% NHG (p > 0.05) was found. Decreasing in the depth of caries lesion was notified by PLM as applying either NHT or NHG as greater than FV, with no reduction in the depth for NT.

Conclusions

Nano-HA both in toothpaste and gel form was capable of remineralization better than fluoride varnish. Comparable remineralization of 20% versus 30% NHG was evidenced. NHG for both concentrations was recommended as a capable remineralizing agent for caries remineralization. Clinical Significance: This study indicated that an application of nano-HA gel is an attractive route to deliver the material and can be more effective and less toxic than conventional formulations and provide its effectiveness directly at the site of action, especially for a noncooperative young child and medicinally intimidated patients who may face with inconvenience in using toothbrush and toothpaste for hygiene control.

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.

Nanobioremediation: A sustainable approach towards the degradation of sodium dodecyl sulfate in the environment and simulated conditions

Nanotechnology has gained huge importance in the field of environmental clean-up today. Due to their remarkable and unique properties, it has shown potential application for the remediation of several pesticides and textile dyes. Recently it has shown positive results for the remediation of sodium dodecyl sulfate (SDS). One of the highly exploited surfactants in detergent preparation is anionic surfactants. The SDS selected for the present study is an example of anionic linear alkyl sulfate. It is utilized extensively in industrial washing, which results in the high effluent level of this contaminant and ubiquitously toxic to the environment. The present review is based on the research depicting the adverse effects of SDS in general and possible strategies to minimizing its effects by bacterial degradation which are capable of exploiting the SDS as an only source of carbon. Moreover, it has also highlighted that how nanotechnology can play a role in the remediation of such recalcitrant pesticides.

Surface Chemistry of Polymers

Surface chemistry plays a key role in modern applications of polymer materials [...]