Person: Guzmán Solís, Eduardo
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First Name
Eduardo
Last Name
Guzmán Solís
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Químicas
Department
Química Física
Area
Química Física
Identifiers
10 results
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Now showing 1 - 10 of 10
Item Ensamblaje Electrostático de sistemas poliméricos cargados: fabricación y propiedades(2015) Guzmán Solís, Eduardo; Ortega Gómez, Francisco; González Rubio, RamónLa Tesis Doctoral presentada consta de un estudio de los procesos de fabricación de monocapas y multicapas de sistemas poliméricas cargados, así como de las propiedades de los sistemas obtenidos. El método de fabricación empleado en todos los sistema s estudiados se basa en la interacción electrostática entre cadenas poliméricas y superficies (o capa poliméricas), de ahí el nombre de ensamblaje electrostático (ESA). En el desarrollo de la Tesis se evalúan los diferentes comportamientos observad os en monocapas y multicapas (obtenidas por la adsorción alternada de monocapas de polímeros con carga opuesta) ante diferentes modificaciones tanto de la naturaleza de los polímeros empleados en la adsorción como de las condiciones de ensamblaje. Pa ra realizar el estudios completo se han empleado diversas técnicas experimentales que permiten la caracterización de estos sistemas tanto durante el proceso de fabricación (D-QCM y elipsometría) como una vez formadas las películas (AFM, XPS, reflecti vidad de neutrones y rayos X, potencial de superficie, potencial ?, ángulo de contacto). Con la batería de técnicas empleadas se ha obtenido información tanto estructural como de los procesos de formación (cinéticas de adsorción) y propiedades (propi edades mecánicas, contenido en agua, carga superficial) de los materiales obtenidos. Los sistemas estudiados presentan ciertas peculiaridades en lo referente a sus procesos de construcción y propiedades, que permiten anticipar posibles aplicaciones de los mismos en diversas áreas de la nanotecnología. Por un lado, la cinética de adsorción de las capas obtenidas para todos los casos ha mostrado un carácter bimodal, con una primera etapa relacionada con la difusión de las cadenas poliméricas hac ia la superficie, seguida de una etapa de reorganización de las cadenas preadsorbidas. Por otro lado, se han observado ciertas propiedades físico-químicas comunes en todos los sistemas, como son un alto grado de hidratación de las películas que lleva a la formación de estructuras altamente plastificadas, similares a un gel polimérico. En lo referente al estudio de las monocapas se ha analizado esencialmente el efecto de la arquitectura molecular y la naturaleza como polielectrolitos de las cadenas empleadas sobre el ensamblaje, siendo el estudio del ensamblaje de monocapas esencial para el posterior estudio realizado de la construcción de multicapas por ensamblaje capa a capa (LbL).Item Particle and Particle-Surfactant Mixtures at Fluid Interfaces: Assembly, Morphology, and Rheological Description(Advances in Condensed Matter Physics, 2015) Maestro, Armando; Santini, Eva; Zabiegaj, Dominika; Llamas, Sara; Ravera, Francesca; Liggieri, Libero; Ortega Gómez, Francisco; González Rubio, Ramón; Guzmán Solís, EduardoWe report here a review of particle-laden interfaces. We discuss the importance of the particle’s wettability, accounted for by the definition of a contact angle, on the attachment of particles to the fluid interface and how the contact angle is strongly affected by several physicochemical parameters. The different mechanisms of interfacial assembly are also addressed, being the adsorption and spreading the most widely used processes leading to the well-known adsorbed and spread layers, respectively. The different steps involved in the adsorption of the particles and the particle-surfactant mixtures from bulk to the interface are also discussed. We also include here the different equations of state provided so far to explain the interfacial behavior of the nanoparticles. Finally, we discuss the mechanical properties of the interfacial particle layers via dilatational and shear rheology. We emphasize along that section the importance of the shear rheology to know the intrinsic morphology of such particulate system and to understand how the flow-field-dependent evolution of the interfacial morphology might eventually affect some properties of materials such as foams and emulsions. We dedicated the last section to explaining the importance of the particulate interfacial systems in the stabilization of foams and emulsions.Item Oil-In-Water Microemulsions for Thymol Solubilization(Colloids and Interfaces, 2019) Fernández Peña, Laura; Gutiérrez Muro, Sonia; Guzmán Solís, Eduardo; Lucia, Alejandro; Ortega Gómez, Francisco; González Rubio, RamónEssential oil compounds (EOCs) are molecules with well-known antimicrobial and antipest activity. However, such molecules possess limited solubility in water, making their handling difficult. This work aimed to enhance the distribution of a solid essential oil compound, thymol, using oil-in-water (o/w) microemulsions for its solubilization. The use of mixtures formed by an alkyl polyglucoside (APG) and soybean lecithin (SL) allowed for stabilization of the o/w microemulsions in a broad range of compositions, with the total concentration of the mixture of the two surfactants (APG+SL) and the APG:SL ratio both being essential for controlling the nature of the obtained dispersions. The microemulsions obtained using oleic acid as the oil phase and with compositions far from those corresponding to the onset of the emulsion region showed a good efficiency for thymol solubilization. This is an advantage from a stability point of view, as well as for ease of thymol preparation. The present work opens new alternatives for designing eco-sustainable formulations for EOC solubilization, with the possibility of preparing the formulations at the place of use, thereby saving transport costs and reducing the emission of pollutants.Item Surfactant-Like Behavior for the Adsorption of Mixtures of a Polycation and Two Different Zwitterionic Surfactants at the Water/Vapor Interface(Molecules, 2019) Akanno, Andrew; Guzmán Solís, Eduardo; Fernández Peña, Laura; Ortega Gómez, Francisco; González Rubio, RamónThe bulk and interfacial properties of solutions formed by a polycation (i.e., poly(diallyl-dimethylammonium chloride), PDADMAC) and two different zwitterionic surfactants (i.e., coco-betaine (CB) and cocoamidopropyl-betaine (CAPB)) have been studied. The bulk aggregation of the polyelectrolyte and the two surfactants was analyzed by turbidity and electrophoretic mobility measurements, and the adsorption of the solutions at the fluid interface was studied by surface tension and interfacial dilational rheology measurements. Evidence of polymer–surfactant complex formation in bulk was only found when the number of surfactant molecules was closer to the number of charged monomers in solutions, which suggests that the electrostatic repulsion associated with the presence of a positively charged group in the surfactant hinders the association between PDADMAC and the zwitterionic surfactant for concentrations in which there are no micelles in solution. This lack of interaction in bulk is reflected in the absence of an influence of the polyelectrolyte in the interfacial properties of the mixtures, with the behavior being controlled by the presence of surfactant. This work has evidenced the significant importance of the different interactions involved in the system for controlling the interaction and complexation mechanisms of in polyelectrolyte–surfactant mixtures.Item Two Different Scenarios for the Equilibration of Polycation—Anionic Solutions at Water–Vapor Interfaces(Coatings, 2019) Guzmán Solís, Eduardo; Fernández Peña, Laura; Akanno, Andrew; Llamas, Sara; Ortega Gómez, Francisco; González Rubio, RamónThe assembly in solution of the cationic polymer poly(diallyldimethylammonium chloride) (PDADMAC) and two different anionic surfactants, sodium lauryl ether sulfate (SLES) and sodium N-lauroyl-N-methyltaurate (SLMT), has been studied. Additionally, the adsorption of the formed complexes at the water–vapor interface have been measured to try to shed light on the complex physico-chemical behavior of these systems under conditions close to that used in commercial products. The results show that, independently of the type of surfactant, polyelectrolyte-surfactant interactions lead to the formation of kinetically trapped aggregates in solution. Such aggregates drive the solution to phase separation, even though the complexes should remain undercharged along the whole range of explored compositions. Despite the similarities in the bulk behavior, the equilibration of the interfacial layers formed upon adsorption of kinetically trapped aggregates at the water–vapor interface follows different mechanisms. This was pointed out by surface tension and interfacial dilational rheology measurements, which showed different equilibration mechanisms of the interfacial layer depending on the nature of the surfactant: (i) formation layers with intact aggregates in the PDADMAC-SLMT system, and (ii) dissociation and spreading of kinetically trapped aggregates after their incorporation at the fluid interface for the PDADMAC-SLES one. This evidences the critical impact of the chemical nature of the surfactant in the interfacial properties of these systems. It is expected that this work may contribute to the understanding of the complex interactions involved in this type of system to exploit its behavior for technological purposes.Item Colloids at Fluid Interfaces(Processes, 2019) Maestro, Armando; Guzmán Solís, EduardoOver the last two decades, understanding of the attachment of colloids to fluid interfaces has attracted the interest of researchers from different fields. This is explained by considering the ubiquity of colloidal and interfacial systems in nature and technology. However, to date, the control and tuning of the assembly of colloids at fluid interfaces remain a challenge. This review discusses some of the most fundamental aspects governing the organization of colloidal objects at fluid interfaces, paying special attention to spherical particles. This requires a description of different physicochemical aspects, from the driving force involved in the assembly to its thermodynamic description, and from the interactions involved in the assembly to the dynamics and rheological behavior of particle-laden interfaces.Item 3D solid supported inter-polyelectrolyte complexes obtained by the alternate deposition of poly(diallyldimethylammonium chloride) and poly(sodium 4-styrenesulfonate)(Beilstein Journal of Nanotechnoly, 2016) Guzmán Solís, Eduardo; Maestro, Armando; Llamas, Sara; Álvarez-Rodríguez, Jesús; Ortega Gómez, Francisco; Maroto-Valiente, Ángel; González Rubio, RamónThis work addresses the formation and the internal morphology of polyelectrolyte layers obtained by the layer-by-layer method. A multimodal characterization showed the absence of stratification of the films formed by the alternate deposition of poly(diallyldimethylammonium chloride) and poly(sodium 4-styrenesulfonate). Indeed the final organization might be regarded as threedimensional solid-supported inter-polyelectrolyte films. The growth mechanism of the multilayers, followed using a quartz crystal microbalance, evidences two different growth trends, which show a dependency on the ionic strength due to its influence onto the polymer conformation. The hydration state does not modify the multilayer growth, but it contributes to the total adsorbed mass of the film. The water associated with the polyelectrolyte films leads to their swelling and plastification. The use of X-ray photoelectron spectroscopy has allowed for deeper insights on the internal structure and composition of the polyelectrolyte multilayers.Item 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, RamónPolyelectrolyte–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.Item 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, RamónItem 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, RamónThe 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.