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 26

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
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.
Probing the effect of the capping polyelectrolyte on the internal structure of Layer-by-Layer decorated nanoliposomes
(Journal Colloid and Interface Science, 2023) Mateos-Maroto, Ana; Rubio, José ; Prévost, Sylvain; Maestro, Armando; González Rubio, Ramón; Ortega Gómez, Francisco; Guzmán Solís, Eduardo
Hypothesis The internal organization of polyelectrolyte layers deposited on colloidal templates plays a very important role for the potential applications of these systems as capsules for drug delivery purposes. Experiments The mutual arrangement of oppositely charged polyelectrolyte layers upon their deposition on positively charged liposomes has been studied by combining up three different scattering techniques and Electronic Spin Resonance, which has provided information about the inter-layer interactions and their effect on the final structure of the capsules. Findings The sequential deposition of oppositely charged polyelectrolytes on the external leaflet of positively charged liposomes allows modulating the organization of the obtained supramolecular structures, impacting the packing and rigidity of the obtained capsules due to the change of the ionic cross-linking of the multi-layered film as a result of the specific charge of the last deposited layer. The possibility to modulate the properties of the LbL capsules by tuning the characteristics of the last deposited layers offers a very interesting route for the design of materials for encapsulation purposes with their properties controlled almost at will by changing the number of deposited layers and their chemistry.
Dilution-controlled deposition of mixtures of a synthetic polycation and a natural origin polyelectrolyte with anionic surfactants on negatively charged surfaces
(Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2024) Puente-Santamaría, Ana; Monge-Corredor, Julia; Ortega Gómez, Francisco; González Rubio, Ramón; Guzmán Solís, Eduardo
The cosmetics industry is constantly seeking sustainable and environmentally friendly ingredients for hair care formulations to replace those traditionally derived from the petrochemical industry. In this context, the substitution of traditional cationic polyelectrolytes, such as poly(diallyldimethylammonium chloride, PDADMAC), by others of natural origin, such as chitosan, is a key challenge to achieve new formulations with a higher degree of naturality and more environmentally friendly without compromising product efficacy. This work investigates the effect of dilution on the phase separation of concentrated binary mixtures of two anionic surfactants (sodium laureth sulfate, SLES, and sodium dodecyl sulfate, SDS) with PDADMAC or chitosan. PDADMAC is a polycation of petrochemical origin, whereas chitosan is obtained from natural resources. Also, how this phase separation affects the formation of conditioning deposits on surfaces that mimic the charge and wettability of damaged hair fibers has been studied. The results show that for polymers of similar molecular weight, the substitution of PDADMAC by a highly charged chitosan is a promising alternative. The deposition is greatly enhanced for model wash formulations containing chitosan after minimal dilution. The results obtained here may pave the way to an important line of research toward improving the sustainability profile of hair care formulations without compromising consumer satisfaction.
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.
Anomalous Colloidal Motion under Strong Confinement
(Small, 2023) Abelenda Núñez, Irene; Ortega Gómez, Francisco; González Rubio, Ramón; Guzmán Solís, Eduardo
Diffusion of biological macromolecules in the cytoplasm is a paradigm of colloidal diffusion in an environment characterized by a strong restriction of the accessible volume. This makes of the understanding of the physical rules governing colloidal diffusion under conditions mimicking the reduction in accessible volume occurring in the cell cytoplasm, a problem of a paramount importance. This work aims to study how the thermal motion of spherical colloidal beads in the inner cavity of giant unilamellar vesicles (GUVs) is modified by strong confinement conditions, and the viscoelastic character of the medium. Using single particle tracking, it is found that both the confinement and the environmental viscoelasticity lead to the emergence of anomalous motion pathways for colloidal microbeads encapsulated in the aqueous inner cavity of GUVs. This anomalous diffusion is strongly dependent on the ratio between the volume of the colloidal particle and that of the GUV under consideration as well as on the viscosity of the particle's liquid environment. Therefore, the results evidence that the reduction of the free volume accessible to colloidal motion pushes the diffusion far from a standard Brownian pathway as a result of the change in the hydrodynamic boundary conditions driving the particle motion
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.
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.
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, Eduardo
We 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.
Physico-chemical study of polymer mixtures formed by a polycation and a zwitterionic copolymer in aqueous solution and upon adsorption onto negatively charged surfaces
(Polymer, 2021) Fernández Peña, Laura; Guzmán Solís, Eduardo; Ortega Gómez, Francisco; Bureau, Lionel; Leonforte, Fabien; Velasco, Dandara; González Rubio, Ramón; Luengo, Gustavo S.
The adsorption of mixtures of charged polymers onto solid surfaces presents a big interest in different technological and industrial fields, and in particular, in cosmetics. This requires to deepen on the most fundamental physico-chemical bases governing the deposition, which is generally correlated to the interactions occurring in solution. This work explores the interaction in solution of model polymer mixtures formed by a cationic homopolymer (poly (diallyl-dimethyl-ammonium chloride), PDADMAC) and a zwitterionic copolymer (copolymer of acrylic acid, 3-Trimethylammonium propyl methacrylamide chloride and acrylamide, Merquat 2003), and the adsorption of such mixtures onto negatively charged surfaces. The analysis of the interactions occurring in solution between both polymers performed using dynamic light scattering (DLS), electrophoretic mobility and viscosity measurements, combined with the study of the deposition of the layers of mixtures containing different weight fractions of each polymer using ellipsometry and quartz crystal microbalance with dissipation monitoring (QCM-D) has shown that the interpolymer complexes formed in solution, and their composition, governs the deposition onto the solid surface and the tribological properties of the adsorbed layers as shown the Surface Force Apparatus (SFA) experiments, allowing for a control of the physico-chemical properties and structure of the layers. Furthermore, the use of Self Consistent Mean Fields Calculations (SCF) confirms the picture obtained from the experimental studies of the adsorbed layers, providing a prediction of the distribution of the polymer chains within the adsorbed layers. It is expected that this study can help on the understanding of the correlations existing between the behavior of future associations of innovative and eco-sustainable polymers and their adsorption processes onto solid surface.