Person:
Guzmán Solís, Eduardo

First Name

Eduardo

Last Name

Guzmán Solís

URI

https://hdl.handle.net/20.500.14352/76095

Affiliation

Universidad Complutense de Madrid

Faculty / Institute

Ciencias Químicas

Department

Química Física

Area

Química Física

Identifiers

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Now showing 1 - 10 of 13

Aqueous dispersions of oleic acid nanodroplets for thymol encapsulation
(Colloids and Surfaces A, 2024) Paula Gutiérrez-González; Peña Fernández, Laura Luisa; Alejandro Lucia; Ortega Gómez, Francisco; González Rubio, Ramón; Guzmán Solís, Eduardo
This study focuses on the use of oleic acid to disperse thymol as nanodroplets, stabilized by a mixture of alkylpolyglucoside and lecithin, in an aqueous environment. This approach aims to develop innovative platforms for the encapsulation and release of poorly water-soluble molecules such as thymol, useful for drug delivery and insecticide systems. The results highlight the critical role of controlling the content and concentration of the oil phase (thymol-oleic acid mixture) in achieving optimal thymol dispersion and nanodispersion stability. The interplay between the ability of oleic acid to inhibit thymol crystallization and the maximum dispersible oil amount is crucial. It affects the dispersion of thymol within the nanodroplets and influences coalescence and Ostwald ripening phenomena. The balance between oleic acid and thymol content is key: while oleic acid stabilizes dispersions, higher thymol content increases droplet size, potentially triggering destabilization. The uneven distribution of thymol within the droplets, revealed by fluorescence spectroscopy, suggests that up to three different chemical environments exist. This investigation may pave the way for the development of efficient platforms to improve access to biologically relevant, poorly soluble molecules.
Ionic strength effect in the equilibrium and rheological behavior of an amphiphilic triblock copolymer at the air/solution interface
(Colloids and Interface, 2024) Carbone, Carlo; Guzmán Solís, Eduardo; Maldonado-Valderrama, Julia; González Rubio, Ramón; Ortega Gómez, Francisco
This study investigates the effect of an inert salt (NaCl) on the equilibrium interfacial tension and dilatational modulus of Pluronic F-68 copolymer, a triblock copolymer consisting of two terminal blocks of poly(ethylene oxide) and a less hydrophilic central block of poly(propylene oxide). Interfacial tension measurements were carried out using a surface force balance and a drop shape tensiometer, while rheological measurements were carried out in two different frequency ranges. This involved the use of the oscillatory barrier/droplet method and electrocapillary wave measurements, complemented by an appropriate theoretical framework. This work aimed to elucidate the influence of NaCl on the interfacial behavior of Gibbs monolayers of Pluronic F-68. In addition, this study highlights some of the technical and theoretical limitations associated with obtaining reliable dilatational rheological data at high frequencies (<1 kHz) using electrocapillary wave measurements. The results provide valuable insights into the interplay between salt presence and interfacial properties of Pluronic F-68 and highlight the challenges of obtaining accurate dilatational rheological data under specific measurement conditions.
Non-equilibrium states in polyelectrolyte-surfactant systems at fluid interfaces: A critical review
(Current Opinion in Colloid and Interface Science, 2024) Ana Puente-Santamaría; Ortega Gómez, Francisco; Armando Maestro; González Rubio, Ramón; Guzmán Solís, Eduardo
Over the last two decades, a significant body of research has been developed trying to understand the association and properties of mixtures formed by oppositely charged polyelectrolytes and surfactants. Particular emphasis has been given to their interfacial properties and the intriguing formation of nonequilibrium states. The synergy between these components at interfaces has attracted considerable attention due to its relevance in various industrial and biological applications. The combination of oppositely charged entities leads to complex interactions that influence the stability and behavior of interfaces. This review critically examines recent advances toward understanding the interfacial behavior when polyelectrolytes and surfactants coexist. Emphasis is placed on the existence of nonequilibrium states, shedding light on transient phenomena and kinetic aspects that play a crucial role in the overall system behavior. This will provide insights into the mechanisms governing the interfacial phenomena in these mixed systems. In summary, this review will contribute to the fundamental understanding of colloidal and interfacial science, offering a valuable perspective on designing and optimizing materials with tailored properties.
Exploring the world of rhamnolipids: A critical review of their production, interfacial properties, and potential application
(Current Opinion in Colloid and Interface Science, 2024) Guzmán Solís, Eduardo; Ortega Gómez, Francisco; González Rubio, Ramón
Rhamnolipids are very promising sugar-based biosurfactants, generally produced by bacteria, with a wide range of properties that can be exploited at an industrial and technological level, e.g. in cosmetics, food science, or oil recovery, to provide benefits for human health and the environment. This has led to intensive research into optimizing their production to increase yields and minimize costs, which is challenging because biotechnological methods for rhamnolipid production result in complex product mixtures and require the introduction of complex separation strategies to ensure the purity of the rhamnolipid obtained. This is an important issue for the introduction of rhamnolipids to the market due to the differences that exist between the properties of the different congeners. This review attempts to provide an overview of the interfacial properties, potential applications, and recent advances in understanding the molecular mechanisms that govern the adsorption to interfaces and assembly in solution of rhamnolipids. In addition, the review also discusses some general aspects related to the production and purification methods of rhamnolipids, highlighting the need for further research to fully exploit their potential. It is hoped that this review will contribute to the growing body of knowledge about rhamnolipids and stimulate further research in this field.
Study of the Liquid/Vapor Interfacial Properties of Concentrated Polyelectrolyte–Surfactant Mixtures Using Surface Tensiometry and Neutron Reflectometry: Equilibrium, Adsorption Kinetics, and Dilational Rheology
(2018) Llamas, Sara; Guzmán Solís, Eduardo; Akanno, Andrew; Fernández-Peña, Laura; Ortega Gómez, Francisco; Campbell, Richard; Miller, Reinhard; González Rubio, Ramón
Effect of molecular structure of eco-friendly glycolipid biosurfactants on the adsorption of hair-care conditioning polymers
(Colloids and Surfaces B: Biointerfaces, 2020) Fernández-Peña, Laura; Guzmán Solís, Eduardo; Leonforte, Fabien; Serrano-Pueyo, Ana; Regulski, Krzysztof ; Tournier-Couturier, Lucie; Ortega Gómez, Francisco; González Rubio, Ramón; Luengo, Gustavo
Pseudo-binary mixtures of different glycolipids, four different rhamnolipids (RL) and an alkyl polyglucoside (APG), with poly(diallyl-dimethylammonium chloride) (PDADMAC) have been studied in relation to their adsorption onto negatively charged surfaces to shed light on the impact of the molecular structure of surfactants from natural sources (instead of synthetic surfactant, such as sodium laureth sulfate) on the adsorption of hair-conditioning polymers. For this purpose, the self-assembly of such mixtures in aqueous solution and their adsorption onto negatively charged surfaces mimicking the negative charge of damaged hair fibres have been studied combining experiments and self-consistent field (SCF) calculations. The results show that the specific physico-chemical properties of the surfactants (charge, number of sugar rings present in surfactant structure and length of the hydrocarbon length) play a main role in the control of the adsorption process, with the adsorption efficiency and hydration being improved in relation to conventional sulfate-based systems for mixtures of PDADMAC and glycolipids with the shortest alkyl chains. SCF calculations and Energy Dispersive X-Ray Spectroscopy (EDS) analysis on real hair confirmed such observations. The results allow one to assume that the characteristic of the surfactants, especially rhamnolipids, conditions positively the adsorption potential of polyelectrolytes in these model systems. This study provides important insights on the mechanisms underlying the performance of more complex but eco-friendly washing formulations
Development of an environmentally friendly larvicidal formulation based on essential oil compound blend to Control Aedes aegypti larvae: correlations between physicochemical properties and insecticidal activity
(ACS Sustainable Chemistry and Engineering, 2020) Lucia, Alejandro; Girard, Clemence; Fanucce, Micaela; Coviella, Carlos; González Rubio, Ramón; Ortega Gómez, Francisco; Guzmán Solís, Eduardo
Oil in water (o/w) emulsions stabilized by an amphiphilic copolymer have been studied in relation to their potential insecticidal activity against Aedes aegypti mosquito larvae. These emulsions contain as the oil phase different blends of two isomeric essential oil compounds, thymol and carvacrol. The results show that the addition of carvacrol facilitates the dispersion of the oil within the aqueous phase, with the stabilization and polydispersity of the emulsions being controlled by the change of the ratio between the copolymer concentration and that of the oil phase (Rcop/EOC). Emulsions containing pure essential oil compounds as the oil phase do not present any significant difference on their larvicidal activity against mosquito larvae, with emulsions containing only thymol being slightly more effective than those containing only carvacrol as the oil phase. Furthermore, the use of blends containing different weight fractions of thymol and carvacrol as the oil phase results in formulations with an additive larvicidal activity in relation to those with the pure compounds. Despite the larvicidal activity of the emulsions, they do not provoke inhibition to the emergence of adult individuals in A. aegypti populations. The spreading and evaporation of the emulsions onto the solid surface, which may be an important parameter for the performance of larvicidal formulations, were found to be dependent on the same parameters that govern the stability of the emulsions. This study helps in seeking new alternatives for the preparation of new eco-sustainable formulations against insect pests.
A closer physico-chemical look to the Layer-by-Layer electrostatic self-assembly of polyelectrolyte multilayers
(Advances in Colloid and Interface Science, 2020) Guzmán Solís, Eduardo; González Rubio, Ramón; Ortega Gómez, Francisco
The fabrication of polyelectrolyte multilayer films (PEMs) using the Layer-by-Layer (LbL) method is one of the most versatile approaches for manufacturing functional surfaces. This is the result of the possibility to control the assembly process of the LbL films almost at will, by changing the nature of the assembled materials (building blocks), the assembly conditions (pH, ionic strength, temperature, etc.) or even by changing some other operational parameters which may impact in the structure and physico-chemical properties of the obtained multi-layered films. Therefore, the understanding of the impact of the above mentioned parameters on the assembly process of LbL materials plays a critical role in the potential use of the LbL method for the fabrication of new functional materials with technological interest. This review tries to provide a broad physico-chemical perspective to the study of the fabrication process of PEMs by the LbL method, which allows one to take advantage of the many possibilities offered for this approach on the fabrication of new functional nanomaterials
Equilibration of a Polycation–Anionic Surfactant Mixture at the Water/Vapor Interface
(Langmuir, 2018) Akanno, Andrew; Guzmán Solís, Eduardo; Fernández Peña, Laura; Llamas, Sara; Ortega Gómez, Francisco; González Rubio, Ramón
The adsorption of concentrated poly(diallyldimethylammonium chloride) (PDADMAC)–sodium lauryl ether sulfate (SLES) mixtures at the water/vapor interface has been studied by different surface tension techniques and dilational viscoelasticity measurements. This work tries to shed light on the way in which the formation of polyelectrolyte–surfactant complexes in the bulk affects the interfacial properties of mixtures formed by a polycation and an oppositely charged surfactant. The results are discussed in terms of a two-step adsorption–equilibration of PDADMAC–SLES complexes at the interface, with the initial stages involving the diffusion of kinetically trapped aggregates formed in the bulk to the interface followed by the dissociation and spreading of such aggregates at the interface. This latter process becomes the main contribution to the surface tension decrease. This work aids our understanding of the most fundamental basis of the physicochemical behavior of concentrated polyelectrolyte–surfactant mixtures which present complex bulk and interfacial interactions with interest in both basic and applied sciences.
Towards understanding the behavior of polyelectrolyte–surfactant mixtures at the water/vapor interface closer to technologically-relevant conditions
(Physical Chemistry Chemical Physics, 2018) Llamas, Sara; Fernández-Peña, Laura; Akanno, Andrew; Guzmán Solís, Eduardo; Ortega, Víctor; Ortega Gómez, Francisco; García Csaky, Aurelio; Campbell, Richard ; González Rubio, Ramón
Polyelectrolyte–surfactant mixtures and their interactions with fluid interfaces are an important research field due to their use in technological applications. Most of the existing knowledge on these systems is based on models in which the polyelectrolyte concentration is around 50 times lower than that used in commercial formulations. The present work marks a step to close the gap on the understanding of their behavior under more practically-relevant conditions. The adsorption of concentrated mixtures of poly(diallyldimethyl-ammonium) chloride and sodium N-lauroyl-N-methyltaurate at the water/vapor interface with a crude mixing protocol has been studied by different surface tension techniques, Brewster angle microscopy, neutron reflectometry, and several bulk characterization techniques. Kinetically-trapped aggregates formed during mixing influence the interfacial morphology of mixtures produced in the equilibrium one-phase region, yet fluctuations in the surface tension isotherm result depending on the tensiometric technique applied. At low bulk surfactant concentrations, the free surfactant concentration is very low, and the interfacial composition matches the trend of the bulk complexes, which is a behavior that has not been observed in studies on more dilute mixtures. Nevertheless, a transition to synergistic co-adsorption of complexes and free surfactant is observed at the higher bulk surfactant concentrations studied. This transition appears to be a special feature of these more concentrated mixtures, which deserves attention in future studies of systems with additional components.