Volume 60, Issue 6

In dilute water-surfactant systems L 3 phases are found in which bilayers interconnect to form a sample-spanning sponge-like structure. From our previous study of the system water/NaCl-AOT (sodium bis(2-ethylhexyl) sulfosuccinate) we know that a transition of this sponge-like structure to an oil-continuous foam-like structure occurs upon addition of minute amounts of oil (about 3 wt%, α = 0.03) in the L 3 channel at a constant surfactant mass fraction of γ = 0.15 and T = 25 °C. The aim of the present study was to verify if the same transition occurs at γ = 0.25. To achieve this goal, we determined the relevant part of the phase diagram and studied the electrical conductivities and viscosities within the narrow one-phase L 3 channel. Although the electrical conductivities and viscosities change qualitatively like those observed at γ = 0.15 we did not observe a sponge-like structure at γ = 0.25 in the oil-free system ( α = 0) with freeze-fracture electron microscopy (FFEM) and freeze fracture direct imaging (FFDI). Together with the FFEM/FFDI images and SANS/SAXS curves we provide experimental evidence for a structural transition with decreasing oil content from a thermodynamically stable foam-like to a thermodynamically stable onion-like nanostructure at γ = 0.25 rather than to a sponge-like structure as is the case at γ = 0.15.

Diffusion-controlled adsorption at the rotating disk is calculated for Frumkin isotherm. The near equilibrium isotherms are simulated and their time components are analysed. The purpose of the work is to investigate the physical meanings of S-shaped isotherms that appear for strong attractions in the adsorbed layer. It is demonstrated that the surface coverage that is created gradually, by the diffusion process, consumes the concentration gradient of the dissolved surfactant in the diffusion layer. Once the equilibrium with the bulk of the solution is established, the driving force of diffusion-controlled adsorption vanishes and no additional adsorption is possible. The diffusion layer thickness on the rotating disk tends to the constant value and the flux depends only on the concentration of dissolved adsorbent at the disk surface. Hence, the equilibrium with the bulk of solution is established faster than at the stationary disk. This equilibrium takes an infinite amount of time to reach, but the system can approach close to the equilibrium within a definite period of time. The near equilibration time depends on the bulk concentration of surfactant. These relationships exhibit sharp maxima under the influence of attractions in the adsorbed layer.

Aluminium foil is a versatile material used in various industries, but its inherent low wettability limits its application. Surfactant can be used as effective agents for enhancing the wettability, enabling improved surface interactions and performance. In this study, we investigated the wettability of anionic (SDS and AOT) and cationic (CTAB) surfactants prepared in water as well as in isopropanol-water solvents with the four different volume fractions (0.1, 0.2, 0.3 and 0.4) on aluminium foil surfaces by measuring the contact angle. As the volume fraction of isopropanol on aluminium foil increases, the contact angle of SDS, CTAB, and AOT increases whereas the surface free energy decreases, indicating the hydrophobic nature of the surface. This trend is observed with the increasing concentrations of various solvents used. The adhesion work exhibits a linear increase with alcohol surface tension. A curvilinear variation is observed in the plots between cos θ $\theta $ and 1/ γ SL $\sqrt{{\gamma }_{\text{SL}}}$ . The plots of adhesion work versus contact angles show non-linear variation. Additionally, the plot of cos θ $\theta $ against the surface tension of alcohol and adhesion work against log C exhibit curvilinear variation. With these results, the article aims to provide valuable insights into the application of surfactants for improving the wettability of aluminium foil.

In this study the interaction between the esterified amide gemini surfactant C 12 -(BAE)-C 12 , where BAE stands for the bis(acetoxy)ethane linking group, and the non-ionic polymer polyvinylpyrrolidone (PVP) was investigated by the surface tension method. It was found that there was no apparent interaction between them. The interaction between C 12 -(BAE)-C 12 and sodium polyelectrolyte polyacrylate (NaPAA) was investigated by surface tension, micropolarity and turbidity measurements. The results showed that there was a strong interaction between them. The aggregates were formed by electrostatic attraction between the molecules of C 12 -(BAE)-C 12 and NaPAA in the bulk. This process led to the appearance of two inflection points, the critical aggregation concentration ( cac ) and the critical micelle concentration (CMC), on the surface tension and micropolarity curves. In addition, the inorganic salt NaBr had two opposite effects, promoting or inhibiting the interaction between C 12 -(BAE)-C 12 and NaPAA. This was related to the concentration of NaBr itself.

The creation and study of artificial membranes based on microemulsions is an important direction due to the similarity of the structure of both direct and reverse microemulsions with cell membranes. A microemulsion mobile phase prepared with a non-ionic surfactant in combination with a C18 type stationary phase creates a similar image of the cell membrane in a chromatographic column. In addition, the use of microemulsion systems to transport drugs with low bioavailability into the body can increase their bioavailability. The chromatographic behaviour of model substances of biomedical importance was investigated using micellar mobile phases containing polyoxyethylene (20) cetyl ether in biopartitioning micellar chromatography (BMC) in the concentration range of 1–5 %. Cholic acid was introduced into the polyoxyethylene (20) cetyl ether micellar mobile phase to approximate the structure of the cell membrane. The hydrophobicity of the model compounds was evaluated. Hydrophobicity indices in the micellar mobile phase with and without addition of cholic acid were compared. The release profile of promethazine hydrochloride from microemulsion systems with monomeric and polymeric surfactants was investigated. The kinetic properties of the release of promethazine hydrochloride from microemulsion systems were calculated. It was found that a microemulsion of polyoxyethylene (20) cetyl ether mixed with polyoxyethylene (4) lauryl ether reduced the release of promethazine hydrochloride in weight percent. The release of promethazine hydrochloride from microemulsions does not obey Fick’s diffusion but follows a non-Fick’s transport mechanism, as evidenced by the high values of the diffusion exponent ( n > 0.5).

In this work, fatty alcohol ethoxylation surfactant PALMEROL 1214 (lauryl myristyl alcohol C 12 –C 14 ) designated as LMA-EO-30 and novel surface-active monomer (surfethoxymers) such as Hemi Ester Lauryl Myristyl Alcohol Malate designated as HELMEM, HELMEI (itaconate) and HELMES (succinate) have been synthesized. These types of non-ionic surfactant have been characterized for their structures using spectroscopic measurements. In addition, their surface-active properties like surface tension, critical micelle concentration (CMC), HLB, the cloud point and foaming properties were investigated. The results indicated that the novel surfethoxymers HELMEM, HELMEI and HELMES exhibit an excellent surface activity and a high performance in the mentioned industrial applications.

In this paper, anionic branched-chain tertiary fatty alcohol sulfate surfactants were synthesized from n -hexene and n -octene using selective olefin dimerization, hydration reaction (hydroxylation), and sulfur trioxide sulfation. The direct hydration reaction of the α-olefin dimer 2-butyl-1-octene with water as a model reaction was explored for the synthesis of branched-chain tertiary fatty alcohols. Two branched-chain tertiary fatty alcohol sulfate surfactants, namely C 12 -SBTAS and C 16 -SBTAS, with different carbon chain lengths, were synthesized by the sulfur trioxide sulfation method. Their structures were confirmed by various analytical techniques, including HPLC, FT-IR, HR-MS, and 1 H NMR. Equilibrium and dynamic surface tension, foaming, wetting, and emulsifying properties were compared with those of Guerbet cetyl alcohol sulfate (C 16 -SGAS). C 12 -SBTAS and C 16 -SBTAS exhibited good surface activity with equilibrium surface tension ( γ CMC ) values of 27.41 mN m −1 and 26.69 mN m −1 , respectively. They also had low foaming and rapid defoaming abilities, as well as good wetting and emulsifying properties, which match the application characteristics of typical branched-chain surfactants.

In this study, special types of washing agents, intended for fruit washing were developed. Fruit washing agents with different contents of non-ionic surfactants have been prepared. The developed products were characterized in terms of performance with regard to their ability to remove pesticide residues from fruit surfaces. Special attention was paid to the safety of use in relation to the level of skin irritation during washing. The results provided important information on the effect of surfactant concentration on selected quality parameters of the developed fruit washing agents.

Among the SARS-CoV-2 vaccines developed to date, the mRNA vaccines developed by the Pfizer/BioNTech and Moderna companies have been formulated using saturated lipids, specifically 1,2-distearoyl- sn -glycero-3-phosphocholine (DSPC), along with cholesterol. DSPC and cholesterol have the disadvantage of causing sclerosis. Therefore, in this study, lipid nanoparticles (LNPs) were prepared and characterized by replacing DSPC with 1,2-dioleoyl- sn -glycero-3-phosphocholine (DOPC) and excluding cholesterol. The results showed that the DOPC-based LNPs had a smaller diameter (75.67 nm) compared to the previous study and the polydispersity index (PI) indicated a good dispersion homogeneity, suggesting size uniformity. Additionally, the LNPs maintained their size between 57 nm and 152 nm and showed stable PI values (0.330–0.393) throughout the 25 days.

Nasal inserts are novel solid, bio-adhesive dosage forms that various methods can prepare. Nasal inserts work on the principle of nasal fluid absorption from the nasal mucosa on administration into the nasal cavity, where it forms gel, avoiding foreign body sensation. They are administered via the nasal route and help to accomplish delayed systemic drug delivery. This investigation aimed to develop lyophilized nasal inserts of diltiazem hydrochloride for the treatment of hypertension using various concentrations of xanthan gum and guar gum. The drug content, surface pH, hydrophilicity studies, water uptake studies, mucoadhesive studies, in vitro drug release studies, and ex vivo permeation studies of the drug-loaded inserts were carried out. It was further characterized and evaluated by differential scanning calorimetry, scanning electron microscopy, X-ray diffraction studies, histological investigation and stability studies. Lyophilized nasal inserts have advantages over other formulations due to their high-water uptake and mucoadhesion properties. The optimized formulation showed no significant changes in the treated nasal mucosa of the goat, and the stability of the formulation was confirmed by stability studies. The nasal insert containing xanthan gum and guar gum (1:3) is the optimized one because of its high drug content and better drug release when compared to other formulations. In conclusion, the novel nasal inserts of diltiazem hydrochloride could be a better alternative for treating hypertension.

Polyglycerol esters (PEGs) which are non-ionic surfactants acting as emulsifiers, wetting agents and viscosity modifying agents are used in the cosmetic, pharmaceutical and food industries. They have been proposed as an alternative to ethoxylated glycol-based non-ionic surfactants due to safety issues. PGEs are composed of fatty acid, which is a lipophilic moiety, and polyglycerol, which is a hydrophilic moiety. They are synthesized by several methods, such as direct esterification of fatty acids and polyglycerols, chemical transesterification of fatty acid methyl esters and polyglycerol, enzymatic transesterification using Lipozyme 435, using glycerol carbonate as raw material, using microwave irradiation, etc. PGEs (Polyglycerol esters) are claimed to be green alternatives to the existing emulsifiers used in the chemical industry as the raw material used for synthesis is obtained from vegetable oils which are renewable, and therefore, eco-friendly surfactants for use in a broad number of applications including food, cosmetics, textiles and personal care. The major challenges in the synthesis of polyglycerol fatty acid esters are to increase yield and control the esterification level while minimising side reactions.