The water sorption of the films of polyacrylic acid, guar gum, gellan gum and PAA-guar, PAA-gellan mixtures of different compositions, prepared at 25°C and 70°C, was studied. The chemical potentials of water Δμ1, polymer component Δμ2, the average Gibbs energy of interaction of polymers and mixtures with water Δgm, the average Gibbs mixing energy of PAA and guar, PAA and gellan Δgx have been determined. It is established that the increase in the preparation temperature significantly enhances the films’ sorption capacity in relation to water. It is determined that the Gibbs mixing energy of polyacrylic acid with guar and gellan are negative for all component ratios (Δgx <0). The second derivative of Gibbs energy for PAA-guar mixtures has different signs, and in a wide range of concentrations of the mixture it is negative. This indicates the absence of compatibility and the formation of two-phase colloidal systems in mixtures of guar with PAA. In contrast to this for PAA-guar mixtures the second derivative of Gibbs energy is positive for all component ratios. This indicates the polymer compatibilityю The increase in the preparation temperature of mixtures leads to an increase in the interaction of the components in the two-phase system, which may be related to the reduction in size of the associates of macromolecules of guar in aqueous solutions. / Изучена равновесная сорбция паров воды пленками полиакриловой кислоты ПАК, гуара геллана и смесями ПАК-гуар разного состава, приготовленными при 25 °C и 70 °C. Рассчитаны разности химических потенциалов воды Δμ1, полимерных компонентов Δμ2, средние удельные энергии Гиббса взаимодействия полимеров и смесей с водой Δgm и друг сдругом Δgx. Установлено, что повышение температуры приготовления пленок значительно увеличивает их сорбционную способность по отношению к воде. Обнаружено, что энергии Гиббса смешения гуара и геллана с полиакриловой кислотой отрицательны при всех соотношениях компонентов (Δgx < 0). Вторая производная энергии Гиббса по составу имеет разные знаки, и для системы гуар – ПАК в широкой области концентраций смеси она отрицательна. Это свидетельствует об отсутствии совместимости и образовании двухфазных коллоидных систем в смесях гуара с ПАК. В противоположность этому для системы ПАК-геллан величина положительна во всей области составов. Это свидетельствует о совместимости полимеров. При этом повышение температуры приготовления смесей приводит к усилению взаимодействия компонентов в двухфазной системе, что может быть связано с уменьшением размеров ассоциатов макромолекул гуара в водных растворах при повышении температуры.

No description available.

Les copolymères à blocs amphiphiles sont des macromolécules composées d’au moins un bloc hydrophile lié chimiquement à un ou plusieurs blocs hydrophobes. En milieu aqueux, ils s’auto-associent pour former des micelles dont les cœurs constitués des blocs hydrophobes sont protégés de l’eau par une couronne constituée des blocs hydrophiles hydratés. La majorité des copolymères à blocs amphiphiles génèrent dans l’eau des micelles « gelées » ne présentant aucun échange de chaînes entre elles. Ceci vient du fait que l’énergie nécessaire pour extraire un bloc hydrophobe du cœur des objets est beaucoup trop importante. Par conséquent, les caractéristiques des micelles sont plus contrôlées cinétiquement que thermodynamiquement. Pour diminuer cette énergie nous avons incorporé des unités hydrophile acide acrylique (AA) dans le bloc hydrophobe de poly(acrylate de n-butyle) (PnBA). L’incorporation de 50% molaire d’unités AA dans le bloc hydrophobe conduit à la formation d’agrégats pH-sensibles dans le cas du dibloc PAA-b-P(AA0.5-stat-nBA0.5) comme montré dans une étude antérieure. Cette thèse a consisté en une analyse quantitative de la dynamique d’auto-association de copolymères dibloc et tribloc amphiphiles à base d’acrylate de n-butyle et d’acide acrylique dont les blocs hydrophobes contiennent 50% d’unités hydrophiles réparties de manière statistique. Les copolymères à blocs ont été synthétisés par polymérisation radicalaire contrôlée par ATRP. L’influence de la concentration, du pH, de la température et de la force ionique sur la structure et les propriétés mécaniques des systèmes auto-assemblés a été systématiquement étudiée. Par diffusion statique de la lumière nous avons montré la présence d’une concentration d’agrégation critique (CAC) au-dessus de laquelle, des micelles de type étoile (dibloc) ou fleur (tribloc) sont formées par auto-association des blocs hydrophobes. A plus fortes concentrations, des interactions répulsives de type volume exclu apparaissent entre les micelles étoiles. Pour les micelles fleurs, à l’inverse des interactions attractives conduisent au pontage des fleurs jusqu’à l’obtention de réseaux tri-dimensionnels au-dessus de la concentration de percolation. Une attraction trop importante entre les fleurs peut même conduire à une séparation de phase à forte force ionique et bas pH. En diffusion dynamique de la lumière, nous avons montré que la formation des réseaux s’accompagnait de l’apparition d’un mode lent dont l’origine a été expliquée par un mouvement balistique d’hétérogénéités relaxées dans les systèmes. La vitesse de relaxation de ces hétérogénéités s’avèrent être dépendantes des propriétés mécaniques des hydrogels. La formation des réseaux et la dynamique d’échange des chaînes ont été étudiées par rhéologie. La viscosité augmente régulièrement avec la concentration jusqu’à la concentration de percolation où une augmentation brusque de la viscosité se produit et un temps de relaxation apparaît. Le temps de vie des ponts a été finement contrôlé et modulé sur plusieurs décades par modification du pH, de la température et de la force ionique. La formation in-situ des hydrogels nous a permis de mettre en évidence un phénomène de vieillissement des réseaux après leur formation avant d’atteindre un état stationnaire. Ce phénomène s’est traduit par une augmentation du temps de relaxation au cours du temps avant d’atteindre une valeur plateau. Ceci nous a également permis de comprendre pourquoi il était possible de générer des réseaux homogènes, par vieillissement, possédant une dynamique extrêmement lente voir nulle. / Amphiphilic block copolymers are macromolecules composed of at least one hydrophilic block chemically linked to one or several hydrophobic blocks. In water, these macromolecules self-assemble to form micelles composed of a hydrophobic core surrounded by a hydrated hydrophilic corona. The majority of amphiphilic block copolymers form “frozen” micelles in aqueous solution. This means that there is no dynamic exchange of chains between micelles because the energy necessary to extract a hydrophobic block from the core of micelles is too high. Consequently, the characteristics of the micelles are controlled kinetically and not thermodynamically. In order to decrease this energy, we have incorporated acrylic acid units (AA) in the hydrophobic block of poly(n-butyl acrylate) (PnBA). It was previously shown that the incorporation of 50% molar of AA units in the hydrophobic block led to generation of pH-sensitive micelles in the case of PAA-b-P(AA0.5-stat-nBA0.5) diblocks. This thesis presents of a quantitative analysis of the dynamics of self-assembled amphiphilic diblock and triblock copolymer based on acrylic acid units and n-butyl acrylate units. The hydrophobic blocks contained 50% of acrylic acids units incorporated randomly. The block copolymers were synthesized by controlled radical polymerization (ATRP). The influence of the concentration, pH, temperature and the ionic strength on the structure and the mechanical properties of the self-assembled systems was systematically studied. At low concentrations, static light scattering measurements showed the formation of star-like micelles (diblock) or flower-like micelles (triblock) above a critical aggregation concentration (CAC). At higher concentrations, purely repulsive excluded volume interactions between micelles appeared in the case of diblock copolymers. In the case of triblock copolymers bridging of flower-like micelles induced in addition attractive interactions leading to network formation above the percolation concentration. At high ionic strength and low pH, we showed that the attraction between flower-like micelles became sufficiently stong to induce phase separation. Dynamic light scattering measurements showed besides a fast mode due to cooperative diffusion, a second slow relaxation mode that appeared at the percolation concentration. The origin of this mode was explained by a balistic motion induced by the relaxation of heterogeneities inside the system. The velocity of heterogeneities was determined by the mechanical relaxation of the hydrogels. The formation of the network and the exchange dynamic of chains were studied by rheology. The viscosity of solutions increased sharply at the percolation concentration. The terminal visco-elastic relaxation time of the network is related to the lifetime of bridges. It could be controlled and tuned over several decades by varing of pH, temperature and the ionic strength. The in-situ formation of networks revealed an aging of networks after their formation before they reached their stationary state. Aging caused a slow increase of the relaxation time before reaching its steady value. This explains why it is possible to generate homogeneous networks even if the network at steady is kinetically frozen.

In the present work, a super water-absorbent poly(acrylic acid) was synthetized by inverse suspension polymerization, using Span60 as the dispersant, toluene as the dispersing organic phase, trimethylolpropane triacrylate as the crosslinking agent, and sodium persulfate as the initiator. The synthesis was conducted in a small-scale glass reactor operated in semi-batch mode. The following reaction conditions were evaluated: effects of initiator concentration, temperature, percentage of multifunctional cross-linker agent and monomer concentration. Also, two important properties were determined, conversion and gel fraction. A kinetic model including a population balance was employed to simulate the process. The proposed model uses the numerical fractionation technique and is capable of predicting the pre-gel and post-gel properties, the effect of the crosslinking agent level on the polymer properties and the dynamic of gelation. The model was compared with the experimental results and showed a satisfactory representation of the system after parameter adjusting. / No presente trabalho, o poli (ácido acrílico) super-absorvente foi sintetizado por polimerização em suspensão inversa, usando Span 60 como o dispersante, tolueno como fase orgânica, trimetilolpropano triacrilato como agente de reticulação e persulfato de sódio como iniciador. A síntese foi conduzida num reator de vidro em escala de bancada, operado em modo semi-batelada-batelada. As seguintes condições da reação foram avaliadas: os efeitos da concentração de iniciador, a temperatura, a porcentagem de agente de reticulação multifuncional e a concentração de monómero. Além disso, foram determinadas propriedades importantes, como a conversão e a fração de gel. Da mesma forma, foi desenvolvido um modelo de balanço populacional para simular o processo em conjunto com a técnica de fracionamento numérico, que é capaz de prever as propriedades pré-gel e pós-gel, o efeito do nível do agente de reticulação no polímero e as propriedades da dinâmica de gelificação. O modelo foi comparado com os resultados experimentais e mostrou uma representação satisfatória do sistema após o ajuste dos parâmetros.

Nos últimos anos, intensos estudos vêm sendo realizados no que se refere a substitutos ósseos biocompatíveis e absorvíveis, notadamente os cimentos ósseos de fosfato de cálcio, para cirurgias de reconstrução e em engenharia de tecidos. Porém os cimentos de fosfato de cálcio desenvolvidos apresentam baixa resistência mecânica quando comparados com os ossos do corpo humano. Neste contexto, a busca por alternativas para minimizar esse problema tem se intensificado. A obtenção de alfa-fosfato tricálcico por outras rotas de síntese, bem como o desenvolvimento de compósitos de fosfatos de cálcio e hidrogéis têm se destacado nesse ramo. O preparo destes compósitos permite combinar excelentes propriedades como: i) osteocondutividade e capacidade de formar ligações com o tecido ósseo proporcionado pelos fosfatos de cálcio e ii) facilidade de adesão e distribuição de células no interior de scaffolds, proporcionado pelo hidrogel. O objetivo do presente trabalho foi o desenvolvimento de uma nova metodologia de obtenção de alfa-fosfato tricálcico, o preparo de composições de cimentos de fosfato de cálcio e de hidrogéis, bem como a obtenção e caracterização de compósitos destes, visando o melhoramento das propriedades para aplicação como biomaterial Foi possível sintetizar alfa-fosfato tricálcico com elevado grau de pureza, utilizando-se o método de reação via úmida. Após estudos da ordem de adição e concentração dos reagentes foi possível definir os melhores parâmetros de síntese. Com isso verificou-se a influência do tempo de moagem nas propriedades dos cimentos, sendo constatado que para o fosfato de cálcio preparado pela metodologia proposta, não há necessidade de moagem adicional. Foram testadas formulações de hidrogéis utilizando N-vinil-2-pirrolidona e ou ácido acrílico, utilizando três iniciadores: azobisisobutironitrila, persulfato de amônio e 1- hidroxiciclohexil fenil cetona. Pela adição de formulações de hidrogéis ao cimento foi possível obter compósitos com maior absorção de água, mantendo as propriedades mecânicas, o que pode permitir uma melhor adesão celular ao implante sem comprometer sua estrutura. O ensaio de citotoxicidade in vitro demonstrou que o cimento sintetizado neste trabalho não apresentou efeito tóxico para as células. Mostrando, ainda, a adesão e proliferação de célulastronco mesenquimais e de uma linhagem de osteoblastos. / In the last years, intensive studies have been conducted regarding the biocompatible and resorbable bone substitutes, notably calcium phosphate bone cements, for reconstructive surgery and tissue engineering. However, the calcium phosphate cements developed exhibit low mechanical strength when compared with the bones of the human body. In this context, the search for alternatives to minimize this problem has intensified. The obtaining of alphatricalcium phosphate by others synthesis routes, as well as development of calcium phosphate and hydrogels composites has been prominent in this branch. The preparation of these composites allows to combine excellent properties such as: i) osteoconductivity and ability to form bonds with bone tissue, afforded by calcium phosphate and ii) ease of adhesion and distribution of cells in the scaffolds inside, provided by hydrogel. The aim of this work was the development of a new methodology to obtaining alpha-tricalcium phosphate, the preparation of calcium phosphate cements and hydrogels compositions, as well as the obtaining and characterization of composites of these, intended to improve the properties for application as biomaterial. It was possible to synthesize alpha-tricalcium phosphate with high purity using the wet method reaction After studies of the addition order and reagents concentration was possible to define the best synthesis parameters. With that it was verified the influence of milling time on the cements properties to being noted that for the calcium phosphate prepared by the proposed method, there is no need additional milling. Were tested hydrogel formulations using N-vinyl-2-pyrrolidone and/or acrylic acid, using three initiators: azobisisobutyronitrile, ammonium persulfate and 1-hydroxycyclohexyl phenyl ketone. By the addition of the hydrogel formulations to the cement was possible to obtain composites with higher water absorption by keeping the mechanical properties, which may permits better vascularization of the implant without compromising its structure. The in vitro cytotoxicity assay demonstrated that the cement synthesized in this work does not show any toxic effect on the cells. Also, showing the adhesion and proliferation of mesenchymal stem cells and an osteoblast line.

Cette thèse rapporte le greffage chimique de brosses de polymères neutres de poly(acrylate de tert-butyle) (PtBA) et de brosses chargées d’acide polyacrylique (PAA) sur des substrats de mica afin d’étudier leur conformation en fonction de la densité de greffage, du pH et de la force ionique. Le greffage est réalisé par polymérisation contrôlée par transfert d’atome (ATRP) initiée depuis la surface de mica afin de contrôler la croissance du polymère et sa densité de greffage. L’étude de la conformation des brosses de PtBA et de PAA a été menée avec la technique AFM en mesurant les épaisseurs des films à sec et gonflés sous différentes conditions de solvant, de pH et de force ionique. Une monocouche d’amorceurs est tout d’abord greffée sur du mica porteur de groupes hydroxyles créés par plasma (Ar/H2O). Cette couche a été caractérisée par des mesures d’angle de contact et par la technique TOF-SIMS. L’amorceur greffé a ensuite permis d’initier l’ATRP directement depuis la surface pour former des brosses neutres de PtBA liés de façon covalente au mica. La croissance linéaire de l’épaisseur du film avec la masse molaire du polymère en solution et le taux de conversion montre que la polymérisation est contrôlée. De plus, la ré-initiation des chaînes greffées atteste du caractère vivant de la polymérisation. L’hydrolyse des brosses de PtBA, confirmée par des mesures d’angle de contact, d’épaisseur et par FT-IR, conduit à des brosses de PAA. Les différentes couches greffées sont stables à l’air, en milieu organique et en milieu aqueux et leur gonflement est réversible. Le degreffage de la couche de PAA est observé suite à une longue exposition à pH basique. Cette étude représente le premier exemple de brosses greffées chimiquement sur du mica par polymérisation initiée depuis la surface. La variation des paramètres de la réaction de greffage de l’amorceur, tels que la concentration et la durée de réaction, a permis de contrôler le taux de recouvrement de l’amorceur et la densité de greffage du polymère. Une grande gamme de taux de recouvrement de l’amorceur est accessible et se traduit par un intervalle de densités de greffage allant de faibles à élevées (e.g. 0,04 chaîne/nm2 à 0,5 chaîne/nm2). L’étude de la conformation des chaînes de PtBA dans le DMF montre que cet intervalle de densités recouvre le régime crêpe au régime brosse. Le gonflement de brosses de PAA et la variation de la hauteur de la brosse L ont été étudiés en fonction de la densité de greffage, du pH et du sel ajouté cs (NaCl). Une transition brusque de collapsée à étirée est observée avec l’augmentation du pH, indépendamment de la densité de greffage. A pH neutre, les brosses sont collapsées et se comportent comme des brosses neutres en mauvais solvant. A pH basique, les brosses sont gonflées et chargées et se trouvent dans un régime de Pincus caractéristique des polyélectrolytes forts. En présence de sel, les charges sont partiellement écrantées et les répulsions électrostatiques dominent toujours dans la brosse. Cette étude contribue à une meilleure compréhension du comportement complexe des brosses de polyélectrolytes faibles et apporte un soutien expérimental à la théorie sur le comportement de ces brosses. / Neutral polymer brushes of poly(tert-butyl acrylate) (PtBA) and polyelectrolyte brushes of poly(acrylic acid) (PAA) were chemically grafted on mica in order to study their conformation as a function of grafting density, pH and ionic strength. The brushes were prepared via surface-initiated atom-transfer radical polymerization (SI-ATRP). This approach allows the control of the polymer growth and of the polymer grafting density. The study of brush conformation was investigated by measuring the dry and the swollen film thicknesses by Atomic Force microscopy (AFM) under various environmental conditions. Mica substrates were activated by a plasma method leading to OH-functionalized surfaces to which a radical initiator was covalently bound using standard siloxane protocols. The initiator grafting on the mica substrate was confirmed by water contact angle measurements and time-of-flight secondary ion mass spectrometry (TOF-SIMS). The covalently immobilized initiator successfully underwent SI-ATRP with tert-butyl acrylate, yielding end-grafted PtBA brushes that are covalently linked to mica. A linear relationship of the polymer thickness with respect to the molecular weight of the free polymer and with respect to the monomer conversion is obtained confirming that SI-ATRP is well controlled. The PtBA brushes were then hydrolyzed to PAA as confirmed by water contact angle measurements, polymer thickness measurements and FT-IR. The grafted layers show a good stability in air, organic solvent and aqueous solution and a reversible swelling. Film cleavage is observed for long exposure time in basic solution. This study represents the first example of chemically grafted brushes on mica via SI-ATRP. The polymer grafting density of poly(tert-butyl acrylate) was controlled by tuning the initiator surface coverage. By adjusting parameters such as the immobilization reaction time and concentration of the initiator, a wide range of initiator surface coverages and hence polymer densities on mica were possible ranging from 0.04 chain/nm2 to 0.5 chain/nm2). The swelling behavior of PAA brushes was investigated as a function of the polymer grafting density, pH and ionic strength cs (NaCl). A sharp transition from collapsed to stretched conformation was found with increasing pH. At neutral pH, the brushes are collapsed and behave like neutral brushes in poor solvent. At high pH, the brushes are swollen and charged and belong to the Pincus regime. In the presence of salt, the Coulombic repulsions are screened. The observed behavior of PAA brushes resembles the one of strong polyelectrolyte brushes. This study contributes to a better understanding of the complex behaviour of weak polyelectrolyte brushes and brings experimental support to theoretical studies.

The self-assembly of polystyrene-stabilized cadmium sulfide nanoparticles (PS-CdS) with amphiphilic stabilizing chains of polystyrene-block-poly(acrylic acid) (PS-b-PAA) into colloidal quantum dot compound micelles (QDCMs) is studied on two-phase gas-liquid segmented microfluidic reactors. The resulting particle sizes are found to arise from the interplay of shear-induced coalescence and particle breakup, depending on a combination of chemical and flow conditions. Variation of water content, gas-to-liquid ratio, and total flow rate, enable control of QDCM sizes in the range of 140 – 40 nm. The flow-variable shear effect on similar microfluidic reactors is then applied to direct the solution self-assembly of a PS-b-PAA block copolymer into various micelle morphologies. The difference between off-chip and on-chip morphologies under identical chemical conditions is explained by a mechanism of shear-induced coalescence enabled by strong and localized on-chip shear fields, followed by intraparticle chain rearrangements to minimize local free energies. Time-dependent studies of these nanostructures reveal that on-chip kinetic structures will relax to global equilibrium given sufficient time off-chip. Further investigations into the effect of chemical variables on on-chip shear-induced morphologies reveal a combination of thermodynamic and kinetic effects, opening avenues for morphology control via combined chemical (bottom-up) and shear (top-down) forces. An equilibrium phase diagram of off-chip micelle morphologies is constructed and used in conjunction with kinetic considerations to rationalize on-chip mechanisms and morphologies, including cylinders and vesicles, under different chemical conditions. Finally, we extend our strategy of two-phase microfluidic self-assembly of PS-b-PAA to the loading of fluorescent hydrophobic probes (pyrene and naphthalene) with different affinities for the PS core. The on-chip loading approach provides a fast alternate to the slow off-chip method, with implications for the potential development for point-of-care devices for drug loading. On-chip loading results indicate that loading efficiencies are dependent on water content and, to a lesser extent, on flow rate; the results also suggest that the on-chip morphologies of the PS-b-PAA micelles are an important factor in the loading efficiencies. / Graduate

Nos últimos anos, intensos estudos vêm sendo realizados no que se refere a substitutos ósseos biocompatíveis e absorvíveis, notadamente os cimentos ósseos de fosfato de cálcio, para cirurgias de reconstrução e em engenharia de tecidos. Porém os cimentos de fosfato de cálcio desenvolvidos apresentam baixa resistência mecânica quando comparados com os ossos do corpo humano. Neste contexto, a busca por alternativas para minimizar esse problema tem se intensificado. A obtenção de alfa-fosfato tricálcico por outras rotas de síntese, bem como o desenvolvimento de compósitos de fosfatos de cálcio e hidrogéis têm se destacado nesse ramo. O preparo destes compósitos permite combinar excelentes propriedades como: i) osteocondutividade e capacidade de formar ligações com o tecido ósseo proporcionado pelos fosfatos de cálcio e ii) facilidade de adesão e distribuição de células no interior de scaffolds, proporcionado pelo hidrogel. O objetivo do presente trabalho foi o desenvolvimento de uma nova metodologia de obtenção de alfa-fosfato tricálcico, o preparo de composições de cimentos de fosfato de cálcio e de hidrogéis, bem como a obtenção e caracterização de compósitos destes, visando o melhoramento das propriedades para aplicação como biomaterial Foi possível sintetizar alfa-fosfato tricálcico com elevado grau de pureza, utilizando-se o método de reação via úmida. Após estudos da ordem de adição e concentração dos reagentes foi possível definir os melhores parâmetros de síntese. Com isso verificou-se a influência do tempo de moagem nas propriedades dos cimentos, sendo constatado que para o fosfato de cálcio preparado pela metodologia proposta, não há necessidade de moagem adicional. Foram testadas formulações de hidrogéis utilizando N-vinil-2-pirrolidona e ou ácido acrílico, utilizando três iniciadores: azobisisobutironitrila, persulfato de amônio e 1- hidroxiciclohexil fenil cetona. Pela adição de formulações de hidrogéis ao cimento foi possível obter compósitos com maior absorção de água, mantendo as propriedades mecânicas, o que pode permitir uma melhor adesão celular ao implante sem comprometer sua estrutura. O ensaio de citotoxicidade in vitro demonstrou que o cimento sintetizado neste trabalho não apresentou efeito tóxico para as células. Mostrando, ainda, a adesão e proliferação de célulastronco mesenquimais e de uma linhagem de osteoblastos. / In the last years, intensive studies have been conducted regarding the biocompatible and resorbable bone substitutes, notably calcium phosphate bone cements, for reconstructive surgery and tissue engineering. However, the calcium phosphate cements developed exhibit low mechanical strength when compared with the bones of the human body. In this context, the search for alternatives to minimize this problem has intensified. The obtaining of alphatricalcium phosphate by others synthesis routes, as well as development of calcium phosphate and hydrogels composites has been prominent in this branch. The preparation of these composites allows to combine excellent properties such as: i) osteoconductivity and ability to form bonds with bone tissue, afforded by calcium phosphate and ii) ease of adhesion and distribution of cells in the scaffolds inside, provided by hydrogel. The aim of this work was the development of a new methodology to obtaining alpha-tricalcium phosphate, the preparation of calcium phosphate cements and hydrogels compositions, as well as the obtaining and characterization of composites of these, intended to improve the properties for application as biomaterial. It was possible to synthesize alpha-tricalcium phosphate with high purity using the wet method reaction After studies of the addition order and reagents concentration was possible to define the best synthesis parameters. With that it was verified the influence of milling time on the cements properties to being noted that for the calcium phosphate prepared by the proposed method, there is no need additional milling. Were tested hydrogel formulations using N-vinyl-2-pyrrolidone and/or acrylic acid, using three initiators: azobisisobutyronitrile, ammonium persulfate and 1-hydroxycyclohexyl phenyl ketone. By the addition of the hydrogel formulations to the cement was possible to obtain composites with higher water absorption by keeping the mechanical properties, which may permits better vascularization of the implant without compromising its structure. The in vitro cytotoxicity assay demonstrated that the cement synthesized in this work does not show any toxic effect on the cells. Also, showing the adhesion and proliferation of mesenchymal stem cells and an osteoblast line.

No description available.

Nos últimos anos, intensos estudos vêm sendo realizados no que se refere a substitutos ósseos biocompatíveis e absorvíveis, notadamente os cimentos ósseos de fosfato de cálcio, para cirurgias de reconstrução e em engenharia de tecidos. Porém os cimentos de fosfato de cálcio desenvolvidos apresentam baixa resistência mecânica quando comparados com os ossos do corpo humano. Neste contexto, a busca por alternativas para minimizar esse problema tem se intensificado. A obtenção de alfa-fosfato tricálcico por outras rotas de síntese, bem como o desenvolvimento de compósitos de fosfatos de cálcio e hidrogéis têm se destacado nesse ramo. O preparo destes compósitos permite combinar excelentes propriedades como: i) osteocondutividade e capacidade de formar ligações com o tecido ósseo proporcionado pelos fosfatos de cálcio e ii) facilidade de adesão e distribuição de células no interior de scaffolds, proporcionado pelo hidrogel. O objetivo do presente trabalho foi o desenvolvimento de uma nova metodologia de obtenção de alfa-fosfato tricálcico, o preparo de composições de cimentos de fosfato de cálcio e de hidrogéis, bem como a obtenção e caracterização de compósitos destes, visando o melhoramento das propriedades para aplicação como biomaterial Foi possível sintetizar alfa-fosfato tricálcico com elevado grau de pureza, utilizando-se o método de reação via úmida. Após estudos da ordem de adição e concentração dos reagentes foi possível definir os melhores parâmetros de síntese. Com isso verificou-se a influência do tempo de moagem nas propriedades dos cimentos, sendo constatado que para o fosfato de cálcio preparado pela metodologia proposta, não há necessidade de moagem adicional. Foram testadas formulações de hidrogéis utilizando N-vinil-2-pirrolidona e ou ácido acrílico, utilizando três iniciadores: azobisisobutironitrila, persulfato de amônio e 1- hidroxiciclohexil fenil cetona. Pela adição de formulações de hidrogéis ao cimento foi possível obter compósitos com maior absorção de água, mantendo as propriedades mecânicas, o que pode permitir uma melhor adesão celular ao implante sem comprometer sua estrutura. O ensaio de citotoxicidade in vitro demonstrou que o cimento sintetizado neste trabalho não apresentou efeito tóxico para as células. Mostrando, ainda, a adesão e proliferação de célulastronco mesenquimais e de uma linhagem de osteoblastos. / In the last years, intensive studies have been conducted regarding the biocompatible and resorbable bone substitutes, notably calcium phosphate bone cements, for reconstructive surgery and tissue engineering. However, the calcium phosphate cements developed exhibit low mechanical strength when compared with the bones of the human body. In this context, the search for alternatives to minimize this problem has intensified. The obtaining of alphatricalcium phosphate by others synthesis routes, as well as development of calcium phosphate and hydrogels composites has been prominent in this branch. The preparation of these composites allows to combine excellent properties such as: i) osteoconductivity and ability to form bonds with bone tissue, afforded by calcium phosphate and ii) ease of adhesion and distribution of cells in the scaffolds inside, provided by hydrogel. The aim of this work was the development of a new methodology to obtaining alpha-tricalcium phosphate, the preparation of calcium phosphate cements and hydrogels compositions, as well as the obtaining and characterization of composites of these, intended to improve the properties for application as biomaterial. It was possible to synthesize alpha-tricalcium phosphate with high purity using the wet method reaction After studies of the addition order and reagents concentration was possible to define the best synthesis parameters. With that it was verified the influence of milling time on the cements properties to being noted that for the calcium phosphate prepared by the proposed method, there is no need additional milling. Were tested hydrogel formulations using N-vinyl-2-pyrrolidone and/or acrylic acid, using three initiators: azobisisobutyronitrile, ammonium persulfate and 1-hydroxycyclohexyl phenyl ketone. By the addition of the hydrogel formulations to the cement was possible to obtain composites with higher water absorption by keeping the mechanical properties, which may permits better vascularization of the implant without compromising its structure. The in vitro cytotoxicity assay demonstrated that the cement synthesized in this work does not show any toxic effect on the cells. Also, showing the adhesion and proliferation of mesenchymal stem cells and an osteoblast line.