Aqueous mixtures of cationic hexadecyltrimethylammonium chloride (CTAC) and nonionic pentaethyleneglycol monododecyl ether (C₁₂E₅) are investigated. Adsorption layer properties are systematically studied within a wide concentration range for a 1:1 molar ratio of the surfactants. Surface tension and dilatational rheology measurements are conducted by profile analysis tensiometry. The interfacial data are juxtaposed to drainage kinetics and stability results for microscopic foam films, investigated by microinterferometric thin liquid film instrumentation. The obtained results give experimental evidence of synergistic interactions in the studied solutions, as compared to the corresponding single surfactant systems. Specific runs of dynamic and equilibrium surface tension curves are registered against the total surfactant quantity; the surface dilatational elasticities for the mixtures are systematically higher. A clear correlation is established between adsorption layer performance and foam film characteristics. The maxima of the film lifetimes are well outlined, and the respective values are shifted towards lower overall concentrations. The reported results substantiate the key role of the adsorption layers, and the surface dilatational properties in particular, for foam film drainage kinetics and stability. The well-expressed synergy observed in adsorption layer and foam film properties suggests the substantial benefits of using mixed surfactant systems in the design and fine-tuning of foam systems for innovative applications.

Amphiphilic fluorocarbon substances are a trending topic of research due to their wide range of applications accompanied by an alarming environmental and health impact. In order to predict their fate in the environment, use them more economically, develop new water treatment methods, etc., a better understanding of their physicochemical behavior is required. Their hydrophobicity in water/oil systems is particularly sensitive to one key thermodynamic parameter: the free energy of transfer of a perfluoromethylene group from oil to water. However, for the –CF₂– moiety, the transfer energy values reported in the literature vary by more than ±25%. Due to the exponential relationship between this energy and the adsorption constants or the partition coefficients, such an uncertainty can lead to orders of magnitude error in the predicted distribution of fluorinated species. We address this problem by presenting an experimental determination of the hydrophobic effect of a –CF₂– moiety with a greater certainty than currently available. The transfer energy is determined by measuring the interfacial tension of water|hexane for aqueous solutions of short-chained fluorotelomer alcohols. The obtained results for the free energy of transfer of a –CF₂– moiety from oil to water are $1.68\pm 0.02\times R{T}_0$, $1.75\pm 0.02\times R{T}_0$, and $1.88\pm 0.02\times R{T}_0$ at 288.15 K, 293.15 K, and 303.15 K, respectively.

Specific self-assembly is registered in aqueous solution formulations based on four-antennary oligoglycines (T4), namely a spontaneous onset of highly ordered nanostructures—tectomers. This phenomenon is initiated by the action of hydrogen-bonding interactions that promote molecular recognition propensities involving Polyglycine-II-type non-canonical architecture. The result is the formation of positively charged supramolecular entities. These have high potential to capture bacterial endotoxins, like lipopolysaccharides (LPSs). By now, it has been established that the overall properties of these systems can be precisely regulated and gradually changed through fine-tuning the parameters in the aqueous environment (composition, pH, etc.). One unexplored option is to clarify the impact of temperature variations. The aim of the present study is to implement systematic investigations on how changes in temperature influence the various options for the removal of trace LPS quantities, captured by the T4 tectomers. The additional goal is to verify the possibility to develop consecutive paths of recovering the extra T4 quantities that have not participated in the formation of T4+LPS complexes. Some prospects for further applications, e.g., in medicine and pharmaceutics, are also generally outlined.

A surfactant’s equilibrium spreading pressure (ESP) is the maximum decrease in surface tension achievable at equilibrium below the Krafft point. Difficulties in measuring the ESP have been noted previously but no well-established experimental protocols to overcome them exist. We present a case study of three solid amphiphiles with different propensities to spread on the air–water interface. Starting with the partially water soluble n-dodecanol (C₁₂H₂₅OH), which spreads instantaneously. The strong Marangoni flows associated with the spreading result in the dislocating of the Wilhelmy plate or crystals attaching to it. A temporary mechanical barrier in front of the spreading crystals mitigates the flows disturbing the plate. Presaturating the subphase with the amphiphile prevents the establishment of dynamic steady states, reduces the standard error by a factor of three and causes faster equilibration. The perfluoroalkylated analog of dodecanol (11:1 fluorotelomer alcohol, C₁₁F₂₃CH₂OH) is slow spreading. With surfactant crystals on the interface, the surface pressure reaches a pre-equilibrium plateau within an hour, followed by equilibration on day-long timescales. We show that it is better to estimate the ESP by averaging the values of multiple pre-equilibrium plateaus rather than waiting for equilibrium to be established. Finally, the nonspreading amphiphile DPPC exhibits a large barrier for the mass transfer from the DPPC crystal to the aqueous surface. This was overcome by introducing a volatile, water-immiscible solvent deposited on the surface next to the crystals to facilitate the spreading process and leave behind a monolayer.

Two-antennary oligoglycines are synthetic, biocompatible bola-amphiphiles composed of homologs with varying hydrophobic-to-hydrophilic ratios. These molecules exhibit a pronounced tendency for self-assembly in aqueous media, resulting in the formation of well-defined supramolecular structures known as tectomers. The present study is focused on one representative of the antennary olygoglycine and investigates its potential as a nanocarrier for hydrophobic drugs. The non-steroidal anti-inflammatory drug indomethacin is used as a model hydrophobic compound. To maximize the entrapment of the drug, we develop an experimental procedure, including the preliminary formation of tectomers at various pH values, followed by the addition of indomethacin. The obtained oligoglycine-indomethacin complexes are further characterized using UV-Vis spectroscopy, Dynamic Light Scattering, and Thin-Liquid-Film techniques. The results demonstrate that the two-antennary oligoglicine effectively captures indomethacin and forms stable complexes in aqueous media. We outline the optimal conditions for drug entrapment and propose hypotheses regarding the mechanisms behind the formation of the mixed complexes. This study advances the understanding of interactions between two-antennary oligoglycines and hydrophobic compounds and highlights their potential for biomedical applications.