Self-aggregation of cationic dimeric surfactants in water–ionic liquid binary mixtures

Photo-Responsive Asymmetric Gemini Azobenzene Surfactants: Synthesis, Characterization, and Application in Intelligent Foams

Gemini surfactants with stimuli-responsive properties have been demonstrated for a broad range of applications. This study presents the synthesis of a series of photoresponsive asymmetric gemini azobenzene-surfactants (AZO-3(OH)-n, n = 12, 14, 16) and characterizes their structures and photoresponsive properties. Surface tension analysis reveals that the surface activities of AZO-3(OH)-n increase with the degree of asymmetry and decrease significantly after ultraviolet (UV) irradiation. Thermodynamic parameters suggest that the micellization process of the AZO-3(OH)-n molecules is spontaneous. TEM combined with dynamic light scattering confirms that trans-AZO-3(OH)-n with higher asymmetry can assemble into vesicles in aqueous solutions that transform into micelles after UV irradiation. Foaming performance studies show concentration-dependent improvements in both foamability and foam stability. However, the changes in the molecular structure and surface activity after UV irradiation lead to a rapid decrease in the foam half-life. The resulting intelligent foams with rapid photoresponsiveness and excellent cycling stability offer a promising strategy for expanding their applications in industrial production.

Imidazolium‐Based Ionic Liquid as Modulator of Physicochemical Properties of Cationic, Anionic, Nonionic, and Gemini Surfactants

The aggregation morphology of 2 cationic surfactants (cetyldimethylethanolammonium bromide and cetyldiethylethanolammonium bromide), an anionic surfactant (sodium dodecylbenzenesulfonate), a nonionic surfactant (Triton X‐100), and 2 gemini surfactants (16‐4‐16,2Br−[butanediyi‐1,4‐bis(dimethyldohexylammonium bromide)] and 16‐6‐16,2Br−[hexanediyi‐1,6‐bis(dimethyldohexylammonium bromide)]) in the presence of the ionic liquid (IL) 1‐ethyl‐3‐methylimidazoliumbromide [Emim][Br] is studied using various techniques such as surface tension, conductivity, and UV–visible and fluorescence spectroscopy. Increasing the concentration of [Emim][Br] results in a decrease in the critical micelle concentration (CMC) value of the surfactants. Various interfacial properties, namely the surface excess concentration (Гmax), minimum area per molecule at the air–water interface (Amin), and surface pressure at the CMC (πcmc), as well as the thermodynamic parameters such as free energy of the given air/water interface (), Gibbs free energy of micelle formation (), Gibbs free energy of micellization per alkyl tail (), Gibbs energy of transfer (), and standard free energy of adsorption () were also investigated. The aggregation number (Nagg) was determined by the fluorescence method. It was observed that Nagg decreased with increasing weight‐percent of the IL.

Microstructure of copolymeric micelles modulated by ionic liquids: investigating the role of the anion and cation

The addition of ionic liquids significantly alters the micellization behaviour of, and has a profound effect on, the micelles of T1304.

Structural, biocomplexation and gene delivery properties of hydroxyethylated gemini surfactants with varied spacer length

Gemini surfactants with hexadecyl tails and hydroxyethylated head groups bridged with tetramethylene (G4), hexamethylene (G6) and dodecamethylene (G12) spacers were shown to self-assemble at the lower critical micelle concentration compared to their conventional m-s-m analogs. The lipoplex formation and the plasmid DNA transfer into different kinds of host cells were studied. In the case of eukaryotic cells, high transfection efficacy has been demonstrated for DNA-gemini complexes, which increased as follows: G6<G4<G12. Different activity series, i.e., G6>G4>G12 has been obtained in the case of transformation of bacterial cells with plasmid DNA-gemini complexes, mediated by electroporation technique. Solely G6 shows transformation efficacy exceeding the control result (uncomplexed DNA), while the inhibitory effect occurs for G4 and G12. Analysis of physico-chemical features of single surfactants and lipoplexes shows that compaction and condensation effects change as follows: G6<G4 ≤ G12, i.e., agree with the order of transfection efficacy, which is supported by membrane tropic properties of G12. On the other hand, gel retardation assay and docking study testify low electrostatic affinity in G12/DNA pair, thereby indicating that hydrophobic effect probably plays important role in the lipoplex formation. Two factors are assumed to be responsible for the inhibition effect of gemini in the case of transformation of bacterial cells. They are (i) an unfavorable influence of cationic surfactants on the electroporation procedure due to depressing the electrophoretic effect; and (ii) antibacterial activity of cationic surfactants that may cause the disruption of integrity of cell membranes.