Adsorption of cationic multicharged surfactants at liquid/gas interface

Interaction, Surface Activity, and Application of Mixed Systems of Alcohol Ether Sulfate Anionic Surfactants with Multiple Ethylene Oxide Groups and Gemini Quaternary Ammonium Surfactant

The surface activities and application properties for the mixtures of cationic surfactants tetramethylene-1,4-bis[N,N-bis(hydroxypropyl)-hexa/decyloxypropylammonium] bromide (GC10-P) and tetramethylene-1,4-bis[N,N-bis(hydroxyethyl)-hexa/decyloxypropylammonium] bromide (GC10-E) and anionic surfactant isomeric sodium fatty alcohol ether sulfates (iso-AE9S) were investigated using both the tensiometry and the conductometry. The interaction parameters and thermodynamic micellization parameters of GC10-P/iso-AE9S and GC10-E/iso-AE9S mixtures were evaluated by Clint-Rubingh and Motomura theoretical models. When the mole fraction of α1 for GC10-P/iso-AE9S mixed system was 0.2, the critical micelle concentration (CMC) reached a minimum of 1.61 × 10-4 mol/L, and the minimum critical micelle concentration of the GC10-E/iso-AE9S mixed system is 2.67 × 10-5 mol/L at α1 = 0.6. The CMC value of the mixed system is 1-2 orders of magnitude lower than that of any single component. The results indicate that the synergistic effects of the investigated mixed systems (evaluated by βm) are in order of GC10-P/iso-AE9S < GC10-E/iso-AE9S, with maximum βm values of -17.98 and -9.78, respectively. The change in zeta potential indicates that the poly(ethylene oxide) chain has weakened the charge density of the hydrophilic headgroup of the anionic surfactant. The interfacial tension at the oil-water interface in the mixed system of anionic/cationic surfactants is lower than that of any single component, exhibiting a higher interfacial activity. The mixed system exhibits a decreased contact angle and superior wetting ability over any single component, and it also enhances foam performance, emulsification performance, and degreasing performance.

Structural Analysis of Aggregates Formed by Linear- and Star-type Quaternary Ammonium Salt-Based Trimeric Surfactants Using Rheology and Small-Angle X-ray Scattering

We performed a structural analysis of aggregates formed by two types of trimeric surfactants based on quaternary ammonium salts─linear-type 3Cnlin-s-Q and star-type 3Cntris-s-Q─featuring varying alkyl chain lengths (n) and spacer chain lengths (s) in aqueous solutions. We performed rheology, dynamic light scattering, and small-angle X-ray scattering measurements on the trimeric surfactants and investigated the effects of the alkyl chain length, spacer chain length, spacer skeleton structure, and surfactant concentration on their aggregation behavior. Linear-type 3C12lin-3-Q transitioned from gel solutions to worm-like micelles at high concentrations, and 3C14lin-3-Q became gel solutions over a wide range of concentrations. In contrast, all other studied surfactants formed ellipsoidal micelles. The minor and major axes of the ellipsoidal micelles formed by liner-type 3Cnlin-3-Q increased with the increasing alkyl chain length. As the spacer chain length of 3Cnlin-s-Q increased from 3 to 6, and as the spacer skeleton expanded from linear-type 3Cnlin-s-Q to star-type 3Cntris-s-Q, the surfactants formed ellipsoidal micelles without the formation of aggregates with a high-order structure, demonstrating this behavior over a broad concentration range.

Multiheaded Cationic Surfactants with Dedicated Functionalities: Design, Synthetic Strategies, Self-Assembly and Performance

Contemporary research concerning surfactant science and technology comprises a variety of requirements relating to the design of surfactant structures with widely varying architectures to achieve physicochemical properties and dedicated functionality. Such approaches are necessary to make them applicable to modern technologies, such as nanostructure engineering, surface structurization or fine chemicals, e.g., magnetic surfactants, biocidal agents, capping and stabilizing reagents or reactive agents at interfaces. Even slight modifications of a surfactant's molecular structure with respect to the conventional single-head-single-tail design allow for various custom-designed products. Among them, multicharge structures are the most intriguing. Their preparation requires specific synthetic routes that enable both main amphiphilic compound synthesis using appropriate step-by-step reaction strategies or coupling approaches as well as further derivatization toward specific features such as magnetic properties. Some of the most challenging aspects of multicharge cationic surfactants relate to their use at different interfaces for stable nanostructures formation, applying capping effects or complexation with polyelectrolytes. Multiheaded cationic surfactants exhibit strong antimicrobial and antiviral activity, allowing them to be implemented in various biomedical fields, especially biofilm prevention and eradication. Therefore, recent advances in synthetic strategies for multiheaded cationic surfactants, their self-aggregation and performance are scrutinized in this up-to-date review, emphasizing their applications in different fields such as building blocks in nanostructure engineering and their use as fine chemicals.

The effectiveness of newly synthesized quaternary ammonium salts differing in chain length and type of counterion against priority human pathogens

Quaternary ammonium salts (QAS) commonly occur as active substances in disinfectants. QAS have the important property of coating abiotic surfaces, which prevents adhesion of microorganisms, thus inhibiting biofilm formation. In this study, a group of nine monomeric QAS, differing in the structure and length of the aliphatic chain (C12, C14, C16) and the counterion (methylcarbonate, acetate, bromide), were investigated. The study included an analysis of their action against planktonic forms as well as bacterial biofilms. The compounds were tested for their anti-adhesion properties on stainless steel, polystyrene, silicone and glass surfaces. Moreover, mutagenicity analysis and evaluation of hemolytic properties were performed. It was found that compounds with 16-carbon hydrophobic chains were the most promising against both planktonic forms and biofilms. Tested surfactants (C12, C14, C16) showed anti-adhesion activity but it was dependent on the type of the surface and strain used. The tested compounds at MIC concentrations did not cause hemolysis of sheep blood cells. The type of counterion was not as significant for the activity of the compound as the length of the hydrophobic aliphatic chain.