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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., Depto. de Química Física, Fac. de Ciencias Químicas, Instituto Pluridisciplinar (IP), TRUE, pub

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., Ministerio de Economía y Competitividad (España), European Commisssion, Depto. de Química Física, Fac. de Ciencias Químicas, TRUE, pub

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., MICINN, European Innovative Training Network-Marie Skłodowska-Curie Action NanoPaInt, Depto. de Química Física, Fac. de Ciencias Químicas, Instituto Pluridisciplinar (IP), TRUE, pub

Polymers and surfactants are used in many technological and industrial applications such as the manufacture of functional materials and coatings, personal care and pharmaceutical products, food science, paints, anti-icing fluids, tertiary oil recovery and the paper industry. Polymer–surfactant mixtures are particularly important in shampoos and conditioners. However, as in almost every other industry over the past five or more decades, the performance of hair care formulations has been significantly improved by the use of petrochemical-derived ingredients. As a result, cosmetic formulations, and hair care formulations in particular, have been based primarily on polymers and surfactants that are neither renewable, nor derived from environmentally friendly processes, nor have a positive environmental impact. This contrasts with the extensive use of natural and renewable products, mainly plant extracts, in cosmetics in ancient times. Therefore, the substitution of currently used ingredients with others of natural origin has been a top priority for the cosmetic industry over the last two decades, and in order to achieve greater consumer acceptance, it is crucial to maintain and, where possible, improve the technical performance of such products. This paper describes the complexities and challenges of developing greener shampoo and conditioner ingredients and formulations to meet current and future needs, and outlines a methodological approach based on model hair surfaces and a selection of appropriate experimental and numerical techniques to achieve our goals. Some encouraging technical routes using biosurfactants, biopolymers and bio-based polymers are presented, along with the significant opportunity to obtain a wide range of green ingredients through molecular design and well-controlled biotechnological processes. Similar concerns apply to other cosmetic products such as waxes, fragrances, bleaching agents, etc., Depto. de Química Física, Fac. de Ciencias Químicas, TRUE, pub, Descuento UCM

The nondiffusive directional transport of micro-cargos, such as colloids, cells, or liposomes, is vital for living organisms, for example in the intracellular transport of cytoplasmic organelles along actin filaments or microtubules, and also in numerous applications in biomedicine and nanotechnology. Mimicking natural designs, the self-assembly capacity of magnetic colloids is studied and exploited to construct different paths along which swarms of magnetic micro/nanoparticles can be guided. Driven transport is possible thanks to the combined effect of the magnetic microstructure of the self-assembled tracks, adsorbed on a solid interface, and the application of a time-dependent magnetic field. Nonadsorbed magnetic particles propel along the pre-formed structures under the action of an externally controllable traveling potential ratchet, like molecular walkers. The transport mechanisms are determined by both the properties of the particles and the configuration of the applied field. Finally, it is shown how the proposed combination of self-assembly and guided transport paves the way to the development of a new class of techniques, able to adapt ad hoc to the environment, and transport of microparticles along irregular profiles and/or crowded conditions. The technological interest is immediate, including drug delivery and controlled guidance of microcargos, in biological environments and microfluidic platforms., Depto. de Química Física, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Químicas, Fac. de Ciencias Físicas, TRUE, pub, Descuento UCM

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., Depto. de Química Física, Fac. de Ciencias Químicas, Instituto Pluridisciplinar (IP), TRUE, pub

MINECO, EU, Depto. de Química Física, Fac. de Ciencias Químicas, TRUE, pub

This work was funded in part by L’Oréal S.A and by MINECO under grant CTQ2016-78895-R. We are grateful to C.A.I. Espectroscopía y Correlación from the UCM for the use of their facilities. We thank Céline Farcet (L’Oréal) for supporting this study., 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, L’Oréal S.A, MINECO, Depto. de Química Física, Fac. de Ciencias Químicas, TRUE, pub

CRUE-CSIC (Acuerdos Transformativos 2023), 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, Depto. de Química Física, Fac. de Ciencias Químicas, Instituto Pluridisciplinar (IP), TRUE, pub

Chitosan-coated Fe3O4nanoparticles were prepared by coprecipitation followed by reactionwith chitosan and different volumes of glutaraldehyde. Coating was modified by varyingthe volume of glutaraldehyde and reaction time. XRD pattern shows maxima compatibleFe3O4structure. FTIR spectroscopía confirms the presence of chitosan, more evident in sam-ples with higher chitosan content, as denoted by TGA. TEM images of samples with lowglutaraldehyde content reveal particles coated with a homogeneous chitosan shell. Mean-while, those prepared with high glutaraldehyde volume show nanoparticles dispersed in anorganic matrix. Samples present almost superparamagnetic behavior with magnetizationsaturation values that are reduced as the content of organic matter increases. Regarding thestability of these samples in solution, the presence of a homogeneous coating improves theinitial suspension, although it does not prevent its subsequent aggregation over time. How-ever, this aggregation process is reduced for sample synthesized with 1 mL of glutaraldehydeafter 6 h of reaction., Fundación Neurociencias y Envejecimiento, MINECO, Depto. de Química Inorgánica, Fac. de Ciencias Químicas, TRUE, pub

This work was funded by MINECO (Spain) under grants CTQ2016-78895-R and PID2019-106557GB-C21, by Banco Santander-Universidad Complutense grant PR87/19-22513 (Spain) and by E.U. on the framework of the European Innovative Training Network-Marie Sklodowska-Curie Action NanoPaint (grant agreement 955612). The authors also acknowledge the financial support received from CONICET and ANPCYT (Argentina). Authors acknowledge to the C.A.I. de Espectroscopí a y Correlacion of the UCM, for the use of ́their facilities., 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., MINECO, Banco Santander-Universidad Complutense, Depto. de Química Física, Fac. de Ciencias Químicas, TRUE, pub

This work was funded by MINECO under grant CTQ2016-78895-R and by Banco Santander Universidad Complutense grant PR87/19-22513. We are grateful to C.A.I. Espectroscopia from the UCM for the use of their facilities, 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, MINECO, Banco Santander - Universidad Complutense, Depto. de Química Física, Fac. de Ciencias Químicas, TRUE, pub

MINECO, EU, Depto. de Química Física, Fac. de Ciencias Químicas, Instituto Pluridisciplinar (IP), TRUE, pub

MICINN, Unión Europea, ILL, Depto. de Química Física, Fac. de Ciencias Químicas, Instituto Pluridisciplinar (IP), TRUE, pub

Las mezclas formadas por polielectrolitos y tensioactivos presentan un creciente interés para la ciencia coloidal como consecuencia de sus múltiples aplicaciones en una gran variedad de campos con interés tecnológico, entre los que cabe destacar las industrias de pintura, cosmética, farmacéutica y alimentaria.1-2 En formulaciones con base acuosa como es el caso de los lodos de perforación y champús, los polielectrólitos presentan un particular interés dada su alta solubilidad, y que posibilitan la obtención de formulaciones con propiedades reológicas únicas, mientras que los surfactantes, los cuales suelen ser también solubles en agua, tiende a adsorberse en superficies disminuyendo la energía de la superficie.3Desde el punto de vista químico, los polielectrolitos son polímeros que contienen grupos iónicos disociados parcialmente en disolución acuosa, estando sus propiedades dominadas por la existencia de fuertes interacciones electrostáticas de largo alcance.1, 4 La interacción de estos poliiones con tensioactivos o proteínas de carga opuesta o neutra da lugar a la formación de complejos polímero-tensioactivo, los cuales desempeñan un papel clave en en multitud de procesos tanto biológicos como industriales...

CRUE-CSIC (Acuerdos Transformativos 2022), The interaction of particles with fluid interfaces is ubiquitous in synthetic and natural work, involving two types of interactions: particle–interface interactions (trapping energy) and interparticle interactions. Therefore, it is urgent to gain a deep understanding of the main forces controlling the trapping of particles at fluid interfaces, and their assembly to generate a broad range of structures characterized by different degrees of order. This Perspective tries to provide an overview of the main contributions to the energetic landscape controlling the assembly of particles at fluid interfaces, which is essential for exploiting this type of interfacial systems as platforms for the fabrication of interface-based soft materials with technological interest., Unión Europea. Horizonte 2020, Ministerio de Ciencia e Innovación (MICINN), Depto. de Química Física, Fac. de Ciencias Químicas, TRUE, pub

CRUE-CSIC (Acuerdos Transformativos 2022), Particles adsorbed to fluid interfaces are ubiquitous in industry, nature or life. The wide range of properties arising from the assembly of particles at fluid interface has stimulated an intense research activity on shed light to the most fundamental physico-chemical aspects of these systems. These include the mechanisms driving the equilibration of the interfacial layers, trapping energy, specific inter-particle interactions and the response of the particle-laden interface to mechanical perturbations and flows. The understanding of the physico-chemistry of particle-laden interfaces becomes essential for taking advantage of the particle capacity to stabilize interfaces for the preparation of different dispersed systems (emulsions, foams or colloidosomes) and the fabrication of new reconfigurable interface-dominated devices. This review presents a detailed overview of the physico-chemical aspects that determine the behavior of particles trapped at fluid interfaces. This has been combined with some examples of real and potential applications of these systems in technological and industrial fields. It is expected that this information can provide a general perspective of the topic that can be exploited for researchers and technologist non-specialized in the study of particle-laden interfaces, or for experienced researcher seeking new questions to solve., Unión Europea. Horizonte 2020, Ministerio de Ciencia e Innovación (MICINN), Depto. de Química Física, Fac. de Ciencias Químicas, TRUE, pub

Fluid/fluid interfaces are ubiquitous in science and technology, and hence, the understanding of their properties presents a paramount importance for developing a broad range of soft interface dominated materials, but also for the elucidation of different problems with biological and medical relevance. However, the highly dynamic character of fluid/fluid interfaces makes shedding light on fundamental features guiding the performance of the interfaces very complicated. Therefore, the study of fluid/fluid interfaces cannot be limited to an equilibrium perspective, as there exists an undeniable necessity to face the study of the deformation and flow of these systems under the application of mechanical stresses, i.e., their interfacial rheology. This is a multidisciplinary challenge that has been evolving fast in recent years, and there is currently available a broad range of experimental and theoretical methodologies providing accurate information of the response of fluid/fluid interfaces under the application of mechanical stresses, mainly dilational and shear. This review focused on providing an updated perspective on the study of the response of fluid/fluid interfaces to dilational stresses; to open up new avenues that enable the exploitation of interfacial dilational rheology and to shed light on different problems in the interest of science and technology.

[EN] Chitosan-coated Fe3O4 nanoparticles were prepared by coprecipitation followed by reaction with chitosan and different volumes of glutaraldehyde. Coating was modified by varying the volume of glutaraldehyde and reaction time. XRD pattern shows maxima compatible Fe3O4 structure. FTIR spectroscopía confirms the presence of chitosan, more evident in samples with higher chitosan content, as denoted by TGA. TEM images of samples with low glutaraldehyde content reveal particles coated with a homogeneous chitosan shell. Meanwhile, those prepared with high glutaraldehyde volume show nanoparticles dispersed in an organic matrix. Samples present almost superparamagnetic behavior with magnetization saturation values that are reduced as the content of organic matter increases. Regarding the stability of these samples in solution, the presence of a homogeneous coating improves the initial suspension, although it does not prevent its subsequent aggregation over time. However, this aggregation process is reduced for sample synthesized with 1 mL of glutaraldehyde after 6 h of reaction., [ES] Se han preparado nanopartículas de Fe3O4 recubiertas con quitosano mediante coprecipitación seguida de reacción con quitosano y diferentes volúmenes de glutaraldehído. El recubrimiento fue modificado a través de la variación del volumen de glutaraldehído y el tiempo de reacción. Los patrones de DRX muestran máximos compatibles con la estructura del Fe3O4. La espectroscopía IRTF confirma la presencia de quitosano, que se hace más evidente para muestras con altos contenidos de quitosano, como se observa mediante ATG. Las imágenes de MET con volumenes pequeños de glutaraldehído revelan partículas recubiertas homogéneamente con una coraza de quitosano. Por su parte, aquellas preparadas con grandes cantidades exhiben nanopartículas dispersas en la matriz orgánica. Las muestras presentan un comportamiento prácticamente superparamagnéticos con valores de magnetización a la saturación que se reducen cuanto mayor es le contenido de materia orgánica. Atendiendo a la estabilidad de las muestras en disolución, la presencia de un recubrimiento homogéneo mejora la suspensión inicial del material, pero no previene la agregación con el tiempo. Sin embargo, este proceso de agregación se ve reducido para la muestra sintetizada con 1 ml de glutaraldehído con un tiempo de reacción de 6 horas.

CRUE-CSIC (Acuerdos Transformativos 2021), The inherent thermodynamic instability of liposomes during production and storage has limited their widespread applications. Therefore, a novel structure of food-grade nanoliposomes stabilized by a 3D organogel network within the bilayer shell was developed through the extrusion process and successfully applied to encapsulate vitamin D3. A huge flocculation and a significant reduction of zeta potential (−17 mV) were observed in control nanoliposomes (without the organogel shell) after 2 months of storage at 4 °C, while the sample with a gelled bilayer showed excellent stability with a particle diameter of 105 nm and a high negative zeta potential (−63.4 mV), even after 3 months. The development of spherical vesicles was confirmed by TEM. Interestingly, the gelled bilayer shell led to improved stability against osmotically active divalent salt ions. Electron paramagnetic resonance confirmed the higher rigidity of the shell bilayer upon gelation. The novel liposome offered a dramatic increase in encapsulation efficiency and loading of vitamin D3 compared to those of control., Union Europea. H2020, Ministerio de Economía y Competitividad (MINECO), Ministerio de Ciencia e Innovación (MICINN), Universidad Complutense de Madrid/Banco de Santander, Shiraz University, Depto. de Química Física, Fac. de Ciencias Químicas, TRUE, pub

CRUE-CSIC (Acuerdos Transformativos 2021), 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., Unión Europea. Horizonte 2020, Ministerio de Economía y Competitividad (MINECO), Ministerio de Ciencia e Innovación (MICINN), Universidad Complutense de Madrid/Banco de Santander, Depto. de Química Física, Fac. de Ciencias Químicas, TRUE, pub

This work presents a simple methodology for coating small unilamellar liposomes bearing different degrees of positive charge with polyelectrolyte multilayers using the sequential layer-by-layer deposition method. The liposomes were made of mixtures of 1,2- dioleyl-sn-glycero-3-phosphocoline and dimethyl dioctadecyl ammonium bromide (DODAB) and coated by alternated layers of the sodium salt of poly(4-styrenesulfonate) (PSS) and poly(allylamine) (PAH) as polyanions and polycations, respectively. The results show that the zeta potential of the liposomes was not very sensitive to the mole fraction of DODAB in the membrane, XD, in the range 0.3 ≤ XD ≤ 0.8. We were able to coat the liposomes with up to four polymer bilayers. The growth of the capsule size was followed by dynamic light scattering, and in some cases, by cryo-transmission electron microscopy, with good agreement between both techniques. The thickness of the layers, measured from the hydrodynamic radius of the coated liposome, depends on the polyelectrolyte used, so that the PSS layers adopt a much more packaged conformation than the PAH layers. An interesting finding is that the PSS amount needed to reach the isoelectric point of the capsules increases linearly with the charge density of the bare liposomes, whereas the amount of PAH does not depend on it. As expected, the preparation of the multilayers has to be done in such a way that when the system is close to the isoelectric point, the capsules do not aggregate. For this, we dropped the polyelectrolyte solution quickly, stirred it fast, and used dilute liposome suspensions. The method is very flexible and not limited to liposomes or polyelectrolyte multilayers; also, coatings containing charged nanoparticles can be easily made. Once the liposomes have been coated, lipids can be easily eliminated, giving rise to polyelectrolyte nanocapsules (polyelectrosomes) with potential applications as drug delivery platforms., Unión Europea. Horizonte 2020, Ministerio de Economía y Competitividad (MINECO), Ministerio de Ciencia e Innovación (MICINN), Universidad Complutense de Madrid/Banco de Santander, Depto. de Química Física, Fac. de Ciencias Químicas, TRUE, pub

CRUE-CSIC (Acuerdos Transformativos 2021), Magnetic colloids adsorbed at a fluid interface are unique model systems to understand self-assembly in confined environments, both in equilibrium and out of equilibrium, with important potential applications. In this work the pearl-chain-like self-assembled structures of superparamagnetic colloids confined to a fluid–fluid interface under static and time-dependent actuations are investigated. On the one hand, it is found that the structures generated by static fields transform as the tilt angle of the field with the interface is increased, from 2D crystals to separated pearl-chains in a process that occurs through a controllable and reversible zip-like thermally activated mechanism. On the other hand, the actuation with precessing fields about the axis perpendicular to the interface induces dynamic self-assembled structures with no counterpart in non-confined systems, generated by the interplay of averaged magnetic interactions, interfacial forces, and hydrodynamics. Finally, how these dynamic structures can be used as remotely activated roller conveyors, able to transport passive colloidal cargos at fluid interfaces and generate parallel viscous flows is shown. The latter can be used in the mixture of adsorbed molecules and the acceleration of surface-chemical reactions, overcoming diffusion limitations., Unión Europea. Horizonte 2020, Ministerio de Ciencia e Innovación (MICINN), Ministerio de Economía y Competitividad (MINECO), Universidad Complutense de Madrid/Banco de Santander, Depto. de Química Física, Fac. de Ciencias Químicas, TRUE, pub

Carbon nanomaterials are widespread in the atmospheric aerosol as a result of the combustion processes and their extensive industrial use. This has raised many question about the potential toxicity associated with the inhalation of such nanoparticles, and its incorporation into the lung surfactant layer. In order to shed light on the main physical bases underlying the incorporation of carbon nanomaterials into lung surfactant layers, this work has studied the interaction at the water/vapor interface of carbon nanosheets (CN) with Langmuir monolayers of 1,2-Dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC), with this lipid being the main component of lung surfactant layers and responsible of some of the most relevant features of such film. The incorporation of CN into DPPC Langmuir monolayers modifies the lateral organization of the DPPC at the interface, which is explained on the basis of two different effects: (i) particles occupy part of the interfacial area, and (ii) impoverishment of the lipid composition of the interface due to lipid adsorption onto the CN surface. This results in a worsening of the mechanical performance of the monolayers which may present a negative impact in the physiological performance of lung surfactant. It would be expected that the results obtained here can be useful as a step toward the understanding of the most fundamental physico-chemical bases associated with the effect of inhaled particles in the respiratory cycle., Ministerio de Economía y Competitividad (MINECO), Banco Santander/Universidad Complutense de Madrid, Depto. de Química Física, Fac. de Ciencias Químicas, TRUE, pub

Synthetic insecticides have been used for a long time as one of the most effective tools for insect pest control. However, the re-emergence of insect pests and their fast development of resistance, as has occurred for pyrethroid-resistant bed bugs Cimex lectularius L., make it necessary to develop new and safe strategies for effective pest control. This has fostered the research on new eco-sustainable formulations based on essential oils, which allows reducing the impact associated with the intensive use of synthetic insecticides on the environment and their effects on human health. This research explores the stability of water/eugenol/ethanol surfactantless emulsions loaded with imidacloprid (0.003 wt%), and their toxicity against a resistant bed bug strain. The results have shown that these emulsions enable the solubilization of a poorly water-soluble drug, such as the imidacloprid, without any significant modification of their stability. Furthermore, the application of the obtained formulations against the pyrethroid-resistant bed bug results in mortality in the 50–85% range upon topical and spray applications, with the increase of the eugenol content enhancing the effectiveness of the formulations. It may be expected that the ternary water/eugenol/ethanol mixtures could be further developed in the preparation of ready to use formulations, enabling the dispersion of insecticides for pest control., Ministerio de Economía y Competitividad (MINECO), Universidad Complutense de Madrid/Banco de Santander, Depto. de Química Física, Fac. de Ciencias Químicas, TRUE, pub

The 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., Ministerio de Economía y Competitividad (MINECO), Depto. de Química Física, Fac. de Ciencias Químicas, TRUE, pub

Essential 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., Ministerio de Economía y Competitividad (MINECO), Depto. de Química Física, Fac. de Ciencias Químicas, TRUE, pub

The 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., Ministerio de Economía y Competitividad (MINECO), Depto. de Química Física, Fac. de Ciencias Químicas, TRUE, pub

En los últimos años, el interés por el conocimiento y la comprensión del comportamiento de los fluidos complejos ha experimentado una gran evolución debido a su participación en distintos campos, incluyendo la cosmética, farmacia y tecnología de los alimentos [1-3]. En particular, el interés por estos sistemas viene desencadenado por su comportamiento en las proximidades de interfases y su capacidad para formar estructuras autoensambladas que permiten la encapsulación de principios activos. De este modo, la aplicación de los fluidos complejos en cosmética ha permitido dar un carácter más funcional a los productos para el cuidado personal..

En los últimos años, el interés por el conocimiento y la comprensión del comportamiento de los fluidos complejos ha experimentado una gran evolución debido a su participación en distintos campos, incluyendo la cosmética, farmacia y tecnología de los alimentos [1-3]. En particular, el interés por estos sistemas viene desencadenado por su comportamiento en las proximidades de interfases y su capacidad para formar estructuras autoensambladas que permiten la encapsulación de principios activos. De este modo, la aplicación de los fluidos complejos en cosmética ha permitido dar un carácter más funcional a los productos para el cuidado personal.., In recent years, the interest for the study of the physico-chemical behavior of complex fluids has undergone a noticeable evolution as result of its extended use in several technological fields including cosmetic, pharmacy and food technology [1-3]. In particular, this interest has been triggered by the behavior of complex fluids close to interfaces and, its ability to form self-assembled structures enabling for the encapsulation of active compounds. Hence, the use of complex fluids in cosmetics has driven the design and fabrication of personal care products which presents a multifunctional character...

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., Ministerio de Economía y Competitividad (España), European Commission, Depto. de Química Física, Fac. de Ciencias Químicas, TRUE, pub

Las mezclas formadas por polielectrolitos y tensioactivos presentan un creciente interés para la ciencia coloidal como consecuencia de sus múltiples aplicaciones en una gran variedad de campos con interés tecnológico, entre los que cabe destacar las industrias de pintura, cosmética, farmacéutica y alimentaria.1-2 En formulaciones con base acuosa como es el caso de los lodos de perforación y champús, los polielectrólitos presentan un particular interés dada su alta solubilidad, y que posibilitan la obtención de formulaciones con propiedades reológicas únicas, mientras que los surfactantes, los cuales suelen ser también solubles en agua, tiende a adsorberse en superficies disminuyendo la energía de la superficie.3Desde el punto de vista químico, los polielectrolitos son polímeros que contienen grupos iónicos disociados parcialmente en disolución acuosa, estando sus propiedades dominadas por la existencia de fuertes interacciones electrostáticas de largo alcance.1, 4 La interacción de estos poliiones con tensioactivos o proteínas de carga opuesta o neutra da lugar a la formación de complejos polímero-tensioactivo, los cuales desempeñan un papel clave en en multitud de procesos tanto biológicos como industriales...

Es importante comenzar encuadrando la tesis globalmente dentro del marco socioeconómico actual y describir su objetivo general, que es la puesta a punto de técnicas microreológicas que permitan obtener información de propiedades de transporte del sistema. El aspecto clave que justi ca esta meta es el tipo de sistema a estudiar, un sistema viscoelástico en el que se puedan medir propiedades microreológicas. Esta tesis se enmarca en el área de la ciencia llamada microreología, que estudia la dependencia del módulo de cizalla complejo de un uido con la frecuencia utilizando el movimiento de partículas suspendidas en él como información experimental. En los últimos años, ha habido un gran avance en la investigación de estos métodos tanto en lo que se re ere a los métodos experimentales como al análisis teórico de los datos. La novedad que introduce la microreología es que se trata de escalas de longitud micrométrica, por lo que se necesitan especiales condiciones para su medición, tales como el tamaño de las partículas, además de la ventaja de poder emplear menor cantidad de muestra. Tanto las técnicas activas y pasivas se basan en la medición del desplazamiento cuadrático medio, a partir del movimiento browniano inherente a las partículas sonda. Las principales técnicas de este tipo que se han utilizado y se describen en profundidad en esta tesis son la dispersión de luz dinámica (DLS) y una variante de ésta que es la espectroscopía de onda difusa (DWS). Otras alternativas son la videomicroscopía o el uso de pinzas ópticas o magnéticas..., This research describes the application of microrheological techniques to study the viscoelasticity of gels as model of weakly ergodic media, during their complex gelation mechanism to make it an interesting prototype for many other gelling systems in order to predict changes in their bulk properties. Microrheology is founded on the pioneering work of researchers such as Weitz and Mason, [1], [2]. In microrheology, the termal motion of probe particles is interpreted in terms of the mechanical properties of the medium in which they are suspended. The motion of the particles can be quanti ed with a variety of techniques which can fall into two classes: those involving active manipulation of probe particles within the sample, and those employing passive observation of thermal uctuations of such probe particles. In either case, the probes used are typically chemically inert spherical beads of between a fraction of a micrometer to several micrometers in diameter. Passive techniques are typically more useful for measuring low values of predominantly viscous moduli, whereas active techniques can extend the measurable range to samples containing signi cant amounts of elasticity and for carrying out measurements outside the linear regime. Active microrheology methods are, for example, optical and magnetic tweezers, atomic force microscopy. Passive methods are particle tracking, dynamic light scattering, di usion wave spectroscopy...

This 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., Ministerio de Economía y Competitividad (MINECO), ESA, EU, ESFCOST, Depto. de Química Física, Fac. de Ciencias Químicas, TRUE, pub

Es importante comenzar encuadrando la tesis globalmente dentro del marco socioeconómico actual y describir su objetivo general, que es la puesta a punto de técnicas microreológicas que permitan obtener información de propiedades de transporte del sistema. El aspecto clave que justi ca esta meta es el tipo de sistema a estudiar, un sistema viscoelástico en el que se puedan medir propiedades microreológicas. Esta tesis se enmarca en el área de la ciencia llamada microreología, que estudia la dependencia del módulo de cizalla complejo de un uido con la frecuencia utilizando el movimiento de partículas suspendidas en él como información experimental. En los últimos años, ha habido un gran avance en la investigación de estos métodos tanto en lo que se re ere a los métodos experimentales como al análisis teórico de los datos. La novedad que introduce la microreología es que se trata de escalas de longitud micrométrica, por lo que se necesitan especiales condiciones para su medición, tales como el tamaño de las partículas, además de la ventaja de poder emplear menor cantidad de muestra. Tanto las técnicas activas y pasivas se basan en la medición del desplazamiento cuadrático medio, a partir del movimiento browniano inherente a las partículas sonda. Las principales técnicas de este tipo que se han utilizado y se describen en profundidad en esta tesis son la dispersión de luz dinámica (DLS) y una variante de ésta que es la espectroscopía de onda difusa (DWS). Otras alternativas son la videomicroscopía o el uso de pinzas ópticas o magnéticas...

La 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 lle

In the last few years, the development of nanoscience and nanotechnology has attracted great interest in different fields. Nanoscience is the science that studies the systems that have at least one of their dimensions of nanometer-size. The study, design, creation, synthesis, manipulation and application of materials, devices and functional systems through control of matter at the nanoscale is known as Nanotechnology. It is frequently considered that the birth of Nanoscience and Nanotechnology goes back to a sentence in a famous conference by Richard Feinman in 1959: There is plenty of room at the bottom. In this conference he suggested the possibility of manufacturing products based on the rearrangement of atoms and molecules. As soon as scientist has begun to manipulate matter at a small scale, new phenomena and properties were founded and nanotechnologiclal methods are used to create inexpensive systems with unique properties. In this way, materials, devices and systems, whose new properties make them useful at physical, chemical and biological levels, are being studied and developed. In 1980 Eric Drexler proposed the concept of "molecular nanotechnology", which focuses on the construction of nanomachines made of atoms that are able to build other molecular components themselves. With the aim of using nanomaterials as carriers of molecules, various types of nanomaterials have been developed such as nanoparticles or carbon nanotubes; and different types of biomaterials such as dendrimers, liposomes or biodegradable polymers. More recently the design of "nanocapsules" has been the object of intense activity. They are hollow nanoscale objects with a roughly spherical shape able to trap small quantities of drugs, enzymes and other catalysts in their interior. Two different regions can be distinguished: the cavity and the coating, which is frequently made of polyelectrolyte multilayers. The best known technique to obtain these systems is by the Layer-by-layer (LbL) or

In the last few years, the development of nanoscience and nanotechnology has attracted great interest in different fields. Nanoscience is the science that studies the systems that have at least one of their dimensions of nanometer-size. The study, design, creation, synthesis, manipulation and application of materials, devices and functional systems through control of matter at the nanoscale is known as Nanotechnology. It is frequently considered that the birth of Nanoscience and Nanotechnology goes back to a sentence in a famous conference by Richard Feinman in 1959: There is plenty of room at the bottom. In this conference he suggested the possibility of manufacturing products based on the rearrangement of atoms and molecules. As soon as scientist has begun to manipulate matter at a small scale, new phenomena and properties were founded and nanotechnologiclal methods are used to create inexpensive systems with unique properties. In this way, materials, devices and systems, whose new properties make them useful at physical, chemical and biological levels, are being studied and developed. In 1980 Eric Drexler proposed the concept of "molecular nanotechnology", which focuses on the construction of nanomachines made of atoms that are able to build other molecular components themselves. With the aim of using nanomaterials as carriers of molecules, various types of nanomaterials have been developed such as nanoparticles or carbon nanotubes; and different types of biomaterials such as dendrimers, liposomes or biodegradable polymers. More recently the design of "nanocapsules" has been the object of intense activity. They are hollow nanoscale objects with a roughly spherical shape able to trap small quantities of drugs, enzymes and other catalysts in their interior. Two different regions can be distinguished: the cavity and the coating, which is frequently made of polyelectrolyte multilayers. The best known technique to obtain these systems is by the Layer-by-layer (LbL) or

La presente Tesis Doctoral recoge el estudio experimental de la dinámica de sistemas poliméricos de diferente naturaleza en geometría restringida, es decir en condiciones de baja dimensionalidad como son las interfases. En concreto, se ha estudiado el comportamiento reológico de compuestos poliméricos en forma de monocapas de Langmuir y de sistemas mixtos constituidos por nanoparticulastensioactivo y proteína-tensioactivo, constituyendo ambos monocapas de Gibbs en interfases aire-agua. Con el propósito de realizar un estudio de la reología de interfases fluidas en una escala espacio-temporal lo más amplia posible se han desarrollado diversas metodologías específicas, las cuales extienden la reología interfacial desde la escala mesoscópica hasta la macroscópica. Tanto la descripción detallada de las metodologías experimentales específicas como los argumentos que avalan las hipótesis de partida, referentes al estudio de la dinámica interfacial de sistemas complejos en formas de monocapas solubles (Gibbs) e insolubles (Langmuir), se encuentran perfectamente formulados en la literatura especializada.

La presente Tesis Doctoral recoge el estudio experimental de la dinámica de sistemas poliméricos de diferente naturaleza en geometría restringida, es decir en condiciones de baja dimensionalidad como son las interfases. En concreto, se ha estudiado el comportamiento reológico de compuestos poliméricos en forma de monocapas de Langmuir y de sistemas mixtos constituidos por nanoparticulastensioactivo y proteína-tensioactivo, constituyendo ambos monocapas de Gibbs en interfases aire-agua. Con el propósito de realizar un estudio de la reología de interfases fluidas en una escala espacio-temporal lo más amplia posible se han desarrollado diversas metodologías específicas, las cuales extienden la reología interfacial desde la escala mesoscópica hasta la macroscópica. Tanto la descripción detallada de las metodologías experimentales específicas como los argumentos que avalan las hipótesis de partida, referentes al estudio de la dinámica interfacial de sistemas complejos en formas de monocapas solubles (Gibbs) e insolubles (Langmuir), se encuentran perfectamente formulados en la literatura especializada.

La 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 lle

A calorimetric, dielectric and dynamic-mechanical study of the dynamics of the poly(t-butyl acrylate) (PtBa) chains has been carried out in a PtBa homopolymer and two polystyrene (PS)-b-PtBa block copolymers with different PtBa chain lengths. The DSC results show that the size of the cooperative rearranging regions is similar in the homopolymers and the copolymers, both for the PtBa rich- and the PS-rich regions. Therefore, no significant contributions are found arising from composition fluctuations in the copolymers. The relaxation map obtained from dielectric relaxation indicates that there are no differences in the temperature dependence of the α-relaxation of the PtBa block in the three samples studied. However, there are larger differences for the values obtained from DMTA experiments. Contrary to the α-relaxation, the relaxation map for the β-transition shows that the characteristic times for the PtBa blocks are smaller in the homopolymer than in the copolymers. In principle, these are unexpected results because the β-relaxations have a more local character than the α-ones. The width of the α-relaxation increases with T for all the samples, and it is slightly larger for the copolymers. The intensity of the α-relaxation is larger (between 3 and 4 times) for the homopolymer. Considering the molecular weights of the PtBa blocks, this effect has to be ascribed to the existence of frozen amorphous PtBa due to the existence of the glassy PS domains in the microphase separated copolymers. Molecular Dynamic Simulations (MDSs) for different sequences of the polymers under study were carried out. The conformational analysis was carried out between 1000 and 1700 K. The analysis of the variation of angles 1 and 2 of the ester group of PtBa points out the existence of a correlation between the conformational changes of the side group of the polymer chains and their relaxational behaviour.