ARAÚJO, Jorge Luiz Bezerra de. Auto-organização de partículas patchy carregadas. 2014. 75 f. Dissertação (Mestrado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2014. / Submitted by Edvander Pires (edvanderpires@gmail.com) on 2014-08-29T19:48:06Z No. of bitstreams: 1 2014_dis_jlbaraujo.pdf: 26529309 bytes, checksum: 0b19a8cf79d0505ad5749c382dddd8c7 (MD5) / Approved for entry into archive by Edvander Pires(edvanderpires@gmail.com) on 2014-08-29T20:27:12Z (GMT) No. of bitstreams: 1 2014_dis_jlbaraujo.pdf: 26529309 bytes, checksum: 0b19a8cf79d0505ad5749c382dddd8c7 (MD5) / Made available in DSpace on 2014-08-29T20:27:12Z (GMT). No. of bitstreams: 1 2014_dis_jlbaraujo.pdf: 26529309 bytes, checksum: 0b19a8cf79d0505ad5749c382dddd8c7 (MD5) Previous issue date: 2014 / The current stage of development of experimental techniques allow the synthesis of particles complex colloidal, whose surface can be precisely "decorated" with physical properties and/or chemical combinations. Such colloids are usually defined as patchy particles. As result of the modification of parts of the surface of such particles, the interaction between them is generally characterized by an anisotropic potential. Study and understand the process of self-organization of this particular system is of great interest both from the scientific point of view as technology, because of its use in functional materials. In this dissertation, we study. The behavior of a two-dimensional system patchy charged particles, in which the surface is decorated with a timely charge sign opposite that located in the particle center. Thus, patchy each particle has a net charge C, which is result of the difference between the point charges on the surface and that in the particle center patchy. This study uses the technique of computer simulation of molecular dynamics to study the process of self-organization of particles patchy depending on the density and temperature. Initially, we present the model of patchy particles studied here and there is the behavior of the interaction energy between two particles and its dependence on load effective particle (liquid charge) and the number of active sites (p) that decorate the surfaces of colloids, called patches . The study of these parameters is important for understanding the self-organized structures obtained. Presents the stable structures of minimum energy a system with p=2 and C=0 as a function of temperature and density. In general, we observe two well defined phases were distinguished by calculation of thermodynamic properties during the simulation. Results for different values of p and C are also presented order to show the influence of this parameter in the system configuration. In general, it is observed that for large values of the charge and/or number of patches, the repulsive potential prevails causing the system to stabilize in a crystalline configuration. On the other hand, for a system composed of particles with a low value of charge and/or the number od patches interaction potential is attractive inducing predominantly resulting composite structures in the form of clusters of ring and lines particles. / O atual estágio de desenvolvimento de técnicas experimentais permite a síntese de partículas coloidais complexas, cuja superfície pode ser precisamente "decorada" com propriedades físicas e/ou químicas diferentes. Tais coloides são usualmente definidos como partículas patchy. Como resultado da modificação de partes da superfície de tais partículas, a interação entre as mesmas é geralmente caracterizada por um potencial anisotrópico. Estudar e compreender o processo de auto-organização desse sistema particular é de grande interesse tanto do ponto de vista científico como tecnológico devido sua utilização em materiais funcionais. Nessa dissertação, estuda-se o comportamento de um sistema bidimensional de partículas patchy carregadas, nas quais a superfície é decorada pontualmente com uma carga de sinal contrário do centro da mesma de modo que cada coloide possua uma carga total C responsável pelo potencial de interação. Neste trabalho foi utilizada a técnica de simulação Dinâmica Molecular para estudar o processo de auto-organização dessas partículas para diversas densidades e temperaturas. Contudo, antes de apresentar resultados numéricos apresenta-se o modelo de partícula patchy e verifica-se o comportamento da energia de interação com dependência na carga efetiva da partícula e com o número de sítios ativos (p) que decoram as superfícies dos coloides, chamados de patches. Nota-se que o estudo de tais parâmetros é fundamental na previsão de estruturas que o sistema se estabiliza. Apresentam-se as estruturas de mínima energia estáveis, de um sistema com p=2 e carga total neutra, em um diagrama de fases com dependência na temperatura e densidade para p=2. Esse diagrama apresenta claramente duas fases bem definidas que foram distinguidas através de cálculos de propriedades termodinâmicas durante a simulação. Resultados para diferente p e carga total também são apresentados a fim de mostrar a influencia do número de patches, e da carga total, na configuração do sistema. Em geral, observa-se que para altos valores da carga total e/ou número de patches de cada partícula, o potencial repulsivo prevalece fazendo com que o sistema se estabilize em uma configuração cristalina. Por outro lado, um sistema composto de partículas com baixo valor de carga total ou numero de patches as partículas apresentam um potencial atrativo induzindo diferentes tipos de configurações no sistema, como, por exemplo, estruturas na forma de anéis e linhas de partículas.

La notion de valence est très répandue à l’échelle de l’atome et est à l’origine de la diversité et des propriétés des composés covalents (molécules, macromolécules, cristaux). L’un des grands challenges à l’heure actuelle est de décliner cette notion de valence à l’échelle des particules, qui pourraient devenir des briques élémentaires programmées, c’est-à-dire la matière première de nouveaux matériaux qui seraient obtenus par assemblage spontané. Dans ce contexte, nous avons développé des particules à patchs possédant à leur surface des discontinuités chimiques et topologiques permettant de limiter le nombre de particules voisines et d’engendrer des interactions directionnelles avec ces dernières. L’objectif de nos travaux consiste dans un premier temps à imiter les hybridations simples de l’atome de carbone divalent (sp), trivalent (sp2) et tétravalent (sp3). Des particules de silice contenant un nombre spécifique de cavités dans lesquelles se trouvent des chaines de polystyrène ont été synthétisées et fonctionnalisées sélectivement. Des molécules colloïdales constituées d’une particule à patchs, au centre, entourée de nanoparticules satellites en nombre contrôlé ont été obtenues par assemblages covalents ou supramoléculaires. Ces premiers clusters miment la géométrie de molécules simples telles que CF4, BF3, CO2 ou H2O. En différenciant des lots de satellites soit par leur taille, soit par leur composition chimique, nous avons montré qu’il est possible d’étendre la formation de molécules colloïdales vers de structures plus complexes du type AXnYm (n+m = 4) ou encore des molécules colloïdales chirales. Enfin, nous avons développé une autre voie permettant d’obtenir de nouveaux atomes colloïdaux contenant un nombre défini de patchs surfaciques de taille contrôlée. / The concept of valence is well-known at the atomic level and is at the origin of the diversity and properties of covalent compounds (molecules, macromolecules, crystals). Nowadays, one of the major challenges is to decline this notion of valence at the scale of colloidal particles, which could become programmed elementary bricks, that is to say the raw material of new materials that would be obtained by spontaneous assembly. In this context, we have developed patchy particles with chemical and topological discontinuities at their surface that limit the number of neighboring particles and induce directional interactions with them. The objective of our work consists first in imitating simple hybridizations of the divalent (sp), trivalent (sp2) and tetravalent (sp3) carbon atoms. The silica particles containing a specific number of cavities in which residues of polystyrene chains are chemically and selectively functionalized. Colloidal molecules consisting of a patchy particle, in the center, surrounded by satellite nanoparticles in controlled number were obtained by covalent or supramolecular routes. These first clusters mimic the geometry of simple molecules such as CF4, BF3, CO2 or H2O. By differentiating batches of satellites either by their size or by their chemical composition, we have shown that it is possible to extend the formation of colloidal molecules to more complex AXnYm (n + m = 4) structures or chiral colloidal molecules. Finally, we have developed another way to obtain new colloidal atoms containing a precise number of surface patches with a controlled area.

Universidade Federal do Cearà / O atual estÃgio de desenvolvimento de tÃcnicas experimentais permite a sÃntese de partÃculas coloidais complexas, cuja superfÃcie pode ser precisamente "decorada" com propriedades fÃsicas e/ou quÃmicas diferentes. Tais coloides sÃo usualmente definidos como partÃculas patchy. Como resultado da modificaÃÃo de partes da superfÃcie de tais partÃculas, a interaÃÃo entre as mesmas à geralmente caracterizada por um potencial anisotrÃpico. Estudar e compreender o processo de auto-organizaÃÃo desse sistema particular à de grande interesse tanto do ponto de vista cientÃfico como tecnolÃgico devido sua utilizaÃÃo em materiais funcionais. Nessa dissertaÃÃo, estuda-se o comportamento de um sistema bidimensional de partÃculas patchy carregadas, nas quais a superfÃcie à decorada pontualmente com uma carga de sinal contrÃrio do centro da mesma de modo que cada coloide possua uma carga total C responsÃvel pelo potencial de interaÃÃo. Neste trabalho foi utilizada a tÃcnica de simulaÃÃo DinÃmica Molecular para estudar o processo de auto-organizaÃÃo dessas partÃculas para diversas densidades e temperaturas. Contudo, antes de apresentar resultados numÃricos apresenta-se o modelo de partÃcula patchy e verifica-se o comportamento da energia de interaÃÃo com dependÃncia na carga efetiva da partÃcula e com o nÃmero de sÃtios ativos (p) que decoram as superfÃcies dos coloides, chamados de patches. Nota-se que o estudo de tais parÃmetros à fundamental na previsÃo de estruturas que o sistema se estabiliza. Apresentam-se as estruturas de mÃnima energia estÃveis, de um sistema com p=2 e carga total neutra, em um diagrama de fases com dependÃncia na temperatura e densidade para p=2. Esse diagrama apresenta claramente duas fases bem definidas que foram distinguidas atravÃs de cÃlculos de propriedades termodinÃmicas durante a simulaÃÃo. Resultados para diferente p e carga total tambÃm sÃo apresentados a fim de mostrar a influencia do nÃmero de patches, e da carga total, na configuraÃÃo do sistema. Em geral, observa-se que para altos valores da carga total e/ou nÃmero de patches de cada partÃcula, o potencial repulsivo prevalece fazendo com que o sistema se estabilize em uma configuraÃÃo cristalina. Por outro lado, um sistema composto de partÃculas com baixo valor de carga total ou numero de patches as partÃculas apresentam um potencial atrativo induzindo diferentes tipos de configuraÃÃes no sistema, como, por exemplo, estruturas na forma de anÃis e linhas de partÃculas. / The current stage of development of experimental techniques allow the synthesis of particles complex colloidal, whose surface can be precisely "decorated" with physical properties and/or chemical combinations. Such colloids are usually defined as patchy particles. As result of the modification of parts of the surface of such particles, the interaction between them is generally characterized by an anisotropic potential. Study and understand the process of self-organization of this particular system is of great interest both from the scientific point of view as technology, because of its use in functional materials. In this dissertation, we study. The behavior of a two-dimensional system patchy charged particles, in which the surface is decorated with a timely charge sign opposite that located in the particle center. Thus, patchy each particle has a net charge C, which is result of the difference between the point charges on the surface and that in the particle center patchy. This study uses the technique of computer simulation of molecular dynamics to study the process of self-organization of particles patchy depending on the density and temperature. Initially, we present the model of patchy particles studied here and there is the behavior of the interaction energy between two particles and its dependence on load effective particle (liquid charge) and the number of active sites (p) that decorate the surfaces of colloids, called patches . The study of these parameters is important for understanding the self-organized structures obtained. Presents the stable structures of minimum energy a system with p=2 and C=0 as a function of temperature and density. In general, we observe two well defined phases were distinguished by calculation of thermodynamic properties during the simulation. Results for different values of p and C are also presented order to show the influence of this parameter in the system configuration. In general, it is observed that for large values of the charge and/or number of patches, the repulsive potential prevails causing the system to stabilize in a crystalline configuration. On the other hand, for a system composed of particles with a low value of charge and/or the number od patches interaction potential is attractive inducing predominantly resulting composite structures in the form of clusters of ring and lines particles.

Au cours ce travail, nous nous sommes intéressés au design de particules plasmoniques pour le contrôle de l’absorption et de l’émission de lumière. Notre stratégie a été de synthétiser des nanoparticules de type cœur@écorce composées d’un cœur d’or et d’une écorce diélectrique de silice contenant des molécules organiques fluorescentes. Nous avons fait varier la distance entre ces dernières et le cœur afin de moduler l’intensité de leur couplage avec les plasmons du métal et d’ainsi contrôler les propriétés optiques des nanoparticules. Nous nous sommes aussi intéressés à l’assemblage de ces nanoparticules sous la forme de supra-particules ou de réseaux bidimensionnels organisés. L’étude des propriétés optiques de ces nouveaux matériaux a permis de mettre en évidence une forte exaltation de l’intensité de fluorescence des particules cœur@écorce quand celles-ci sont confinées entre deux nappes métalliques, ce qui correspond à un mode de cavité fort. Nous avons également travaillé sur la synthèse de particules composées d’un cœur de silice et soit d’une écorce d’or présentant des patchs « vierges », soit d’une écorce de dioxyde de titane comportant des patchs recouverts de nanoparticules d’or. / During this work, we were interested in the design of plasmonic particles for the control of the absorption and the emission of light. Our strategy was to synthesize core@shell nanoparticles made of a gold core and a silica shell containing fluorescent organic molecules. We have varied the distance between the emitters and the core in order to tune their coupling with the plasmons of gold. We thus tuned the optical properties of the particles. We were also interested in the assembly of these nanoparticles to get supra-particles or organized two-dimensional networks. The study of optical properties of these new materials showed that the exaltation of the fluorescence is maximal when the core@shell particles are confined between two gold boundaries, this situation corresponding to a strong cavity mode. We also worked on the synthesis of particles consisting of a silica core and either a gold shell with bare patches or a titanium dioxide shell with patches covered with gold nanoparticles.

Cette étude porte sur l’assemblage de particules à patchs pour obtenir de nouveaux matériaux. L’étatde l’art a permis de choisir et de mettre en oeuvre une stratégie originale dont la force motrice est l’assemblageinduit en milieu solvant, c’est-à-dire basé sur le caractère collant des macromolécules de polystyrène (PS)lorsqu’elles sont soumises à un mélange d’un bon et d’un mauvais solvant. Nous avons étudié l’assemblage enclusters, en chaînes ou en monocouches de nanoparticules (NPs) de silice possédant respectivement un, deux outrois patchs, constitués de macromolécules de PS greffées à des endroits spécifiques de leur surface. Les NPs desilice à un patch, présentant un rapport de taille patch/particule contrôlable, ont été synthétisées avec succès parune étape de séparation de phases induit par gonflement suivie d’un dépôt de silice régiosélectif. Leur assemblagea été réalisé dans des mélanges binaires DMF/éthanol. Les effets de la qualité du solvant, de la force decentrifugation, de la concentration en NPs, de la durée d'incubation et du rapport de taille patch/particule ont étéétudiés et discutés. La stratégie a été étendue pour obtenir des clusters à base d’or. Les NPs de silice à deuxpatchs ont été préparées par un procédé de polymérisation en émulsion ensemencée du styrène et le rapport detaille patch/particule a été ajusté via le taux de recroissance du noyau de silice. L’assemblage en chaînes des NPsa été réalisé dans des mélanges THF/solution aqueuse de NaCl en faisant varier la concentration en NaCl, lerapport volumique THF/eau, la durée d’incubation, la concentration en NPs et le rapport de tailles patch/particule.Nous avons montré que la cinétique de croissance des chaînes est typique d’une croissance par étapes. Desstratégies pour imiter des homopolymères, des copolymères statistiques, des copolymères séquencés à blocs etdes polymères ramifiés ont été mises en oeuvre, en utilisant comme briques de base des NPs à un patch, des NPsà deux patchs avec des tailles ou des fonctions de surface différentes et/ou des NPs à trois patchs. Les NPs desilice à trois patchs ont été obtenues par la même voie de synthèse que celles à deux patchs. Pour les assemblerdans des structures 2-D en nid d'abeille, nous avons utilisé la technique de Langmuir et nous avons étudiél'influence de différents paramètres expérimentaux. Une étape de recuit sous vapeur de THF a été mise en oeuvre,ce qui a permis de renforcer mécaniquement l’assemblage, mais sans effet significatif sur la compacité. / This study deals with the assembly of patchy particles to get new materials. The state-of-the-art allowedus to select and implement an original strategy whose driving force is the solvent-induced assembly, i.e. based onthe stickiness of polystyrene (PS) macromolecules when they are subjected to a mixture of good and bad solvents.We investigated the assembly into clusters, chains or monolayers of one-patch, two-patch or three-patch silicananoparticles (NPs), respectively, the patches being PS macromolecules grafted at specific positions on theirsurface. One-patch silica NPs with controllable patch-to-particle size ratio were successfully synthesised throughphase separation and site-specific silica coating. Their assembly was performed in DMF/ethanol binary mixtures.The effect of the solvent quality, centrifugation force, particle concentration, incubation time and patch-to-size ratiowas investigated and discussed. The strategy was spread to obtain gold-coated clusters. The two-patch silica NPswere prepared through a seed-growth emulsion polymerisation of styrene and the patch-to-particle size ratio wasadjusted through the extent of the silica core regrowth. The chaining of the NPs was efficiently achieved in theTHF/NaCl aqueous solution mixtures by varying the NaCl concentration, solvent quality, incubation time, NPsconcentration and patch-to-particle size ratio. We showed that the kinetics of the chaining process is characteristicof a reaction-controlled step-growth polymerisation. Strategies to mimic homopolymers, random copolymers, blockcopolymers and branched polymers were implemented by using one-patch NPs, two-patch NPs with different sizes/surface chemical functions and/or three-patch NPs as building units. The three-patch silica NPs were obtainedthrough the same synthetic pathway than two-patch ones. For assembling them in honeycomb-like 2-D structures,we used the Langmuir technique.and we studied the influence of different experimental parameters. THF vapourannealing was implemented to reinforce mechanically the assembly but without significative effect on the packingdensity.

Les méta-matériaux sont une nouvelle classe de matériaux composites artificiels quiprésentent des propriétés inédites. Ils sont typiquement sous divisés en unité appelées méta-atomes.Un design approprié de ces méta-atomes, architecturés à l’échelle nanométrique, permet d’induire despropriétés aussi extraordinaires qu’un indice de réfraction négatif. Dans ce contexte, nous avonsdéveloppé des particules à patchs, capable de développer des interactions selon des directionsprédéterminées. Des clusters multipodiques fait de ces particules (diélectrique) entourées d’un nombrecontrôlé de satellites plasmoniques (or) ont été développés. Nous nous sommes focalisés sur desclusters isotropes, dérivant de géométries tétraédriques, octaédriques et icosaédriques (trois des cinqsolides de Platon). Pour cela, nous avons utilisé des clusters silice/polystyrène, obtenus parpolymérisation ensemencée en émulsion, qui ont servi de préformes. Ils ont ainsi permis d’obtenir desparticules dont les patchs sont en fait des fossettes au fond desquelles subsiste un résidu de chaînespolystyrène greffées. En modifiant chimiquement ces chaînes, nous avons permis soit l’accrochage aufond de ces fossettes de colloïdes d’or puis leur croissance, soit l’accostage de satellites de silice surlesquels nous avons ensuite fait croître une coquille d’or. La seconde voie à offert un meilleur contrôlede la morphologie des clusters et notamment de la distance entre les satellites d’or (quelquesnanomètres) qui est primordiale pour assurer un couplage plasmonique optimal. Les propriétés desclusters obtenus ont été modélisées et mesurées. / Metamaterials are a novel class of artificial composite materials, typically made of subunit called meta-atoms and exhibiting unusual properties. Such meta-atoms, have to be architecturedat the nanometric level, to induce as extraordinary properties as a negative refractive index. In thiscontext, we developed patchy particles, capable to create interactions along predetermined directions.Multipodic clusters made of those (dielectric) particles surrounded by a controlled number ofplasmonic satellites (gold) were developed. We focused on isotropic clusters deriving fromtetrahedral, octahedral and icosahedral geometry (three of the fifth Platonic solids). For that purpose,we used silica/polystyrene clusters, obtained from seeded emulsion polymerization, as template. Byderiving those clusters, patchy particles bearing dimples containing grafted residual polystyrene chainswere obtained. By chemically deriving those chains, we explored two synthetic pathways, thedecoration of the dimples with gold colloids subsequently grown or the anchoring of silica satellitesonto which gold shells were subsequently grown. The second one was prove to offer a better controlover the cluster morphology as well as the inter-satellites gap (few nanometer) which is pivotal toensure an optimal plasmonic coupling. Then, the optical properties of the as obtained clusters weresimulated and measured.

Proteinadsorption ist in vielen biotechnologischen Anwendungen ubiquitär und ein zentrales Forschungsfeld in der Physik der weichen Materie. Das Verstehen der treibenden Kräfte hinter der Proteinadsorption würde zu einer besseren Kontrolle des Adsorptionsprozesses führen und die Entwicklung von Biosystemen mit beispielloser Funktionalität ermöglichen. In der vorliegenden Arbeit wird die Proteinadsorption an weichen polymerartigen Biomaterialien sowie deren physikalische Wechselwirkungen unter Verwendung von zwei unterschiedlichen neu entwickelten Ansätzen theoretisch untersucht. Im ersten Teil wird ein neues mehrkomponentiges kooperatives Bindungsmodell entwickelt, um die Gleichgewichts-Adsorption von Proteinen auf Mikrogelen zu beschreiben. Es war somit möglich, die wahre treibende Kraft der Proteinadsorption zu identifizieren, die hauptsächlich elektrostatischen Ursprungs ist. Eine Errungenschaft des kooperativen Bindungsmodells ist die Vorhersage der kompetitiven Proteinadsorption und -desorption auf das Mikrogel, die auf thermodynamischen Parametern der Adsorption von Proteinen einzelner Sorten basiert. Vergleiche zwischen Experimenten mit binären Proteinmischungen und theoretischen Berechnungen zeigten sehr gute Übereinstimmungen. Der zweite Teil fokussiert auf Protein-Wechselwirkungen mit Polyelektrolyten, um Adsorptionsprozesse auf mikroskopischer Ebene zu erklären. Dafür wurden geladene fleckige Partikel konstruiert und als Proteinmodelle verwendet, während ein einfaches Kugel-Feder-Modell für das Polyelektrolyt und Polyelektrolytbürste benutzt wurde. Ein zentraler Aspekt war die Bestimmung der freien Energie, das Potential der mittleren Kraft (PMF), für die Komplexbildung der beiden Bestandteile mit Vergleichen zur Modellentwicklungen. Die Simulationsergebnisse legen ein komplexes Wechselspiel von elektrostatischen Kräften und Ionenfreisetzungsmechanismen dar, die für die starken attraktiven Wechselwirkungen in den PMFs verantwortlich sind. / Protein adsorption is ubiquitous in many biotechnological applications and has become a central research field in soft matter. Understanding the driving forces behind protein adsorption would allow a better control of the adsorption process and the development of biosystems with unprecedented functionality. In this thesis, protein adsorption onto soft polymeric biomaterials and their physical interactions is studied theoretically by using two different and newly developed approaches. In the first part, a novel multi-component cooperative binding model is developed to describe the equilibrium adsorption of proteins onto microgels. It was thus possible to correctly identify the true driving force behind the protein adsorption which was found to be mainly of electrostatic origin. A key achievement by the cooperative binding model is the prediction of competitive protein adsorption and desorption onto the microgel that is based on thermodynamic parameters related to single-type protein adsorption without any variable parameters. Comparisons between experimental data of binary protein mixtures and theoretical calculations have shown excellent agreements. The second part is focused on protein interactions with polyelectrolyte materials to elucidate adsorption processes on a microscopic level. For this purpose, charged patchy particles are constructed and used as protein models while a simple bead-spring model is employed for the polyelectrolyte and polyelectrolyte brush. A central aspect was the determination of the associated free energy, the potential of mean force (PMF), on the complex formation between the two constituents with comparisons to theoretical model developments. The simulation results evidenced a complex interplay of electrostatic forces and ion release mechanisms to be responsible for the strong attractive interactions observed in the PMFs.