Laboratory 6.2 “Disperse systems and rheology in clean technologies” within WP 6 “Nano-structured materials and disperse systems in clean technologies” aims at the development of new systems for clean technologies and nanotechnologies in various scientific and technological areas: new cleaning agents for hard surfaces; encapsulation and controlled release of reagents; wetting and dewetting processes. The main objectives are to conduct experimental and theoretical research and development of new dispersed systems through the inclusion of new raw materials and innovative materials, and to develop and apply theoretical models of the interactions and stability of complex dispersed systems. High scientific output of Lab 6.2 is manifested via 21 scientific publications in the fields of Dispersion Chemistry, Chemical and Materials Sciences for the period 2018 – 2024 (8 articles in Q1 journals, 6 in Q2, and 7 materials in Q4). Optimized compositions of cleaning formulations for hard surfaces with sulfonated methyl esters have been obtained [1]. New theoretical models for the interactions that determine the structures in micellar systems have been developed and applied [2]. New phenomena such as vortexing [3] and nanoemulsification [4] have been described. New methods have been proposed for obtaining emulsions and foams from triglyceride phases [5]. The role of the components and compositions for the rheology [6], wetting, and cleaning [7] has been demonstrated.

Cryogenic transmission electron microscopy (Cryo-TEM) provides direct visualization of bicontinuous sponge (L₃) phases, where a surfactant bilayer meanders through space, dividing solvent into two continuous domains. Temperature increase destabilizes lamellar order by lowering the bending rigidity and driving the Gaussian modulus toward values that favor handle formation. We captured this transition as the loss of layered registry and the emergence of a labyrinthine bilayer network rich in saddle regions. A Cahn-Hilliard-type phase-field model reproduces these features: small shifts in the free-energy landscape and interfacial penalty are sufficient to convert stripe-like lamellae into bicontinuous structures. This synergy between imaging and modeling highlights how thermal fluctuations push membranes into topologies inaccessible at lower temperatures, offering a predictive framework for designing temperature-responsive surfactant systems.

Kappa carrageenan (KC), a sulfated polysaccharide derived from red seaweed, exhibits distinct gelation properties that are influenced by ionic strength and thermal conditions. While its behavior in aqueous media is well-established, understanding KC’s gelation mechanisms in non-aqueous solvents (like glycerol) remains limited. This study investigates the conformational and rheological properties of kappa carrageenan in glycerol, focusing on the effects of sodium salts (NaCl, NaH2PO4, Na3PO4) at varying concentrations and preparation temperatures (60 °C and 80 °C). Rheological measurements reveal distinct viscosity trends influenced by salt type and temperature, highlighting the interplay between ionic interactions and KC’s conformational transitions. Phosphate salts significantly enhance network elasticity and stability, especially at intermediate concentrations, whereas NaCl induces weaker, viscosity-dominated structures. Atomic force microscopy imaging provides complementary nanoscale insights, showcasing salt-specific structural transitions from looped to branched networks, alongside a temperature-dependent helix-to-coil transformation. These results illustrate how the precisely tuning ionic conditions and the preparation temperatures in glycerol media can effectively modulate KC’s structure and viscoelastic properties. This deeper understanding facilitates targeted design and optimization of carrageenan-based materials across food, pharmaceutical, cosmetic, and biotechnological applications.

Oppositely charged polymer–surfactant mixtures exhibit unique bulk and interfacial properties with many applications. In particular, cationic polymers paired with anionic surfactants are often used to deposit oils and lubricants on hair and skin upon dilution. These dilution-deposition systems are widely studied in simple mixtures but rarely in complex formulations. Thus, our paper focuses on cationic polysaccharides (cat-Guars and cat-HECs) paired with the anionic surfactant SLES-1EO (sodium laureth-1 sulfate) and incorporated into shampoos. We analyzed the polymer–surfactant complexes’ (PSCs) phase behavior, adsorption at the silicone oil/water interface, stickiness to bubbles (and drops), and deposition on hair-like substrates via phase behavior analysis, zeta potential measurements, foam film experiments, and imaging ellipsometry. Our results showed that the cat-Guar/SLES-1EO complexes exhibit wider precipitation regions and higher adsorption at the silicone oil/water interface than the cat-HEC/SLES-1EO complexes. Foam film experiments implied that only the cat-Guar/SLES-1EO complexes bridge the air bubbles (and silicone drops to hair) as they form sticky PSCs. Imaging ellipsometry revealed that cat-Guars deposit thick, inhomogeneous layers of PSCs and silicone on the hair-like substrates, whereas cat-HECs deposit thinner layers or nothing. Together, these findings elucidate the underlying deposition mechanism and offer strategies to optimize the polymer performance in shampoo formulations via a comprehensive experimental protocol.

Hypothesis
Polyglycerol esters of fatty acids are generated via the esterification of a polydisperse mixture of polyglycerol with naturally derived fatty acids. The polymerization process of polyglycerol results in the production of various oligomers, ranging from di-, tri-, and higher-order forms, which contribute to the complexity of final products. The combination of complementary experimental techniques and adequate theoretical interpretations can reveal the wide variety of their physicochemical properties.

Experiments
The colloid and interface properties of polyglyceryl mono-laurate, mono-stearate, mono-oleate, and a mixture of mono-caprylate and mono-caprate esters solutions were characterized by measurements of the electrolytic conductivity, static and dynamic surface tension, aggregate and micelle sizes and distributions, thin liquid film stability and stratification, and solubility in aqueous and in oil phases. The formation, stability, and bubble size distribution of foams generated from polyglycerol esters aqueous solutions were systematically investigated.

Findings
The low concentrations of double-tail molecules and fatty acids in polyglycerol esters affect considerably their micellar, aggregation, and vesicle formations in aqueous solutions. The theoretical data interpretation of polyglycerol esters isotherms and thin liquid films data provide information on the adsorption energies, excluded areas per molecule, interaction parameters of molecules at interfaces, surface electrostatic potential, and the size of micelles. Polyglyceryl mono-oleate exhibits spontaneous emulsification properties. Short chain length polyglycerol esters have excellent foaming ability but relatively low foam stability. The optimal weight fractions of the short-chain polyglyceryl esters and polyglyceryl mono-stearate mixtures with respect to good foaminess and foam stability upon Ostwald ripening are obtained. The reported physicochemical characterization of the water-soluble polyglycerol esters could be of interest to increase the range of their applicability in practice.