O copolímero SBS é o aditivo mais empregado mundialmente na modificação de ligantes asfálticos, por melhorar diversas de suas características. Um dos principais problemas deste tipo de formulação é a separação de fases, que pode ser minimizada com a incorporação de aditivos. Um novo polietileno de alta densidade e baixo peso molecular oxidado (com denominação comercial TITAN 9686) foi utilizado nesta pesquisa, com o objetivo de testar a hipótese de que a adição de proporções adequadas deste aditivo possa melhorar as características reológicas do asfalto+SBS. O experimento laboratorial foi delineado com base na técnica de experimentos com misturas, englobando um total de nove formulações compostas com asfalto, SBS e TITAN. O teor de SBS variou entre 0 e 5% em peso e o de polietileno variou entre 0 e 2% em peso. Foi utilizado óleo aromático no teor de 4% em peso para todas as nove misturas. As misturas foram analisadas em três condições de envelhecimento: virgem, curto prazo (na estufa RTFO) e longo prazo (na estufa PAV). Foram realizados os seguintes ensaios reológicos: (i) de cisalhamento em regime oscilatório em diferentes condições de temperatura e frequência (para medida do módulo complexo e do ângulo de fase, usados na determinação do grau de desempenho, no cálculo dos parâmetros G*/sen(δ) e G*.sen(δ) e na construção de curvas-mestre), (ii) de viscosidade Brookfield, (iii) de fluência e recuperação sob múltiplas tensões (para medida do percentual de recuperação e da compliância não-recuperável), (iv) de varredura de amplitude linear (para cálculo do parâmetro a f e para ajuste do modelo de fadiga) e (v) de estabilidade à estocagem. Acerca das características escolhidas para mensurar a melhora ou piora das propriedades das misturas asfalto+SBS com a adição de TITAN, podem ser feitas as seguintes observações: (i) a estabilidade à estocagem é melhorada com a adição de TITAN, em particular no teores entre 1 e 2%; (ii) a sensibilidade ao envelhecimento tanto a curto quanto a longo prazos diminui com a adição de TITAN; (iii) a adição de TITAN aumenta a resistência à deformação permanente, à luz dos parâmetros Jnr e R e aumenta a sensibilidade dos ligantes asfálticos modificados com SBS a mudanças bruscas nos níveis de tensão aplicados; e (iv) a adição de TITAN contribui com o aumento da resistência à fadiga, à luz dos parâmetros Nf , a baixos níveis de deformação, e af , e a prejudica reduzindo o parâmetro Nf a altos níveis de deformação e aumentando a temperatura crítica de fadiga ou o parâmetro G*.sen(δ). Tendo por base estas evidências, é possível concluir que a adição de TITAN, em linhas gerais, melhorou a estabilidade dos ligantes asfálticos modificados com até 5,0% de SBS. Com base nas análises realizadas, é possível afirmar que teores da ordem de 1 a 2% de TITAN, para teores de SBS entre 3,0 e 5,0%, são recomendáveis, à luz das propriedades, índices e parâmetros analisados neste trabalho. / The SBS copolymer is the most widely used additive in asphalt binder modification, since it enhances many of the properties of the original material. A critical problem that arises from this type of modification is phase separation, which can be minimized by adding other modifiers to the formulation. A new oxidized, high-density polyethylene with low molecular weight (commercial designation of \"TITAN 9686\") was used in the study with the purpose of verifying the hypothesis that the addition of suitable contents of this modifier can improve the rheological properties of the SBS-modified binder. The laboratory matrix of formulations was based on the experiments with mixtures, and nine types of materials were prepared with asphalt binder, SBS and TITAN. The SBS contents ranged from 0 to 5% by weight, whereas the polyethylene contents ranged from 0 to 2% by weight. These formulations also contained 4% of aromatic oil by weight. Three aging conditions were selected: unaged, short-term aged in the rolling thin-film oven (RTFO) and long-term aged in the pressurized aging vessel (PAV). The following tests were carried out: (i) dynamic oscillatory shear at different temperatures and frequencies of loading for the determination of the complex modulus, the phase angles and the master curves, as well as the performance grades and the numerical values of the parameters G*/sin(δ) and G*.sen(δ); (ii) rotational viscosity; (iii) creep and recovery at multiple stress levels for the determination and the percent recovery and the nonrecoverable compliance; (iv) linear amplitude sweep, in order to calculate the parameter a f and fit the fatigue model to the data; and (v) storage stability. With respect to the characteristics used in the evaluation of the properties of the AC+SBS mixtures after the addition of TITAN, the following observations can be made: (i) storage stability is improved when TITAN is added to the formulation, especially at contents ranging from 1 to 2%; (ii) the sensitivity to the short-term and long-term aging processes decreased with the incorporation of TITAN; (iii) the changes in the R and the Jnr values indicate that the addition of TITAN makes the asphalt binder more resistant to rutting, and also increases the sensitivity of the SBS-modified binders to sudden increases in the stress level; and (iv) the presence of TITAN in the material leads to an increase in the fatigue resistance as based on the parameters Nf and af at low strain levels and the increases in the critical fatigue temperature and the parameter G*.sen(δ). With reference to these evidences, it is possible to conclude that the addition of TITAN generally improves the storage stability of the SBS-modified binders with no more than 5% of copolymer by weight. Based on the results of the present study, it is possible to say that percentages between 1 and 2% of TITAN by weight are recommended for SBS contents between 3 and 5% by weight.

No description available.

La Compaction à Grande Vitesse (CGV) est un procédé efficace pour mettre en oeuvre par frittage, et dans un temps court, des poudres polymères semi-cristallins quelle que soit leur viscosité en partant d’une température inférieure au point de fusion. L’échauffement et la fusion du matériau est obtenu par une succession d’impacts à une énergie donnée ce qui offre la possibilité de définir finement la quantité d’énergie que l’on souhaite apporter au matériau et la qualité du frittage. Une fusion partielle de la poudre permet de profiter de la cristallinité élevée de la poudre native, un compromis est alors possible entre de hautes propriétés élastiques et une ductilité élevée. La contre-partie de cette efficacité est une mise au point délicate du procédé. Dans le cas du polyéthylène ultra haute masse molaire (UHMWPE), il a été montré que le procédé permet une quasi-abstraction des effets de la masse molaire. Le frittage du UHMWPE demande seulement une réorganisation à courte distance des chaînes qui peut se faire dans un temps très limité. La cohésion de la poudre est assurée essentiellement par la cocristallisation et la création de nouveaux enchevêtrements. La modélisation du procédé a permis de comprendre comment l’énergie cinétique lors des impacts est transformée en chaleur dans la poudre et elle a permis l’établissement d’un critère de processabilité par CGV. Ce critère de processabilité repose sur la déformabilité de la poudre contenu dans la matrice au moment de l’impact. Celle-ci doit être suffisante pour que l’énergie dissipée dans le matériau permette sa fusion en moins de cent coups. Ceci a permis de comprendre pourquoi le polyoxyméthylène peut difficilement se mettre en forme par CGV. / High Velocity Compaction (HVC) is an efficient process to mold, in a short time, semicrystalline polymers powders any about their viscosity by starting from a temperature below melting point. Heating and melting occur by successive impacts at a preset energy that offers the possibility to set accurately the energy amount that we would bring to the material and the sintering quality. Partial melting of powder enable to take advantage of the high cristallinity of nascent powders, a compromise is possible between high elastic properties and high ductility. The flip-side of this efficiency is a delicate process settings. For the ultra high molecular weight polyethylene (UHMWPE), it has been shown that the process makes it possible a quasi abstraction of molecular weight effects. UHMWPE sintering needs only a short length reorganisation of chains that could be done in a really short time. Powder cohesion is essentially bring by cocrystallisation and by new entanglements creation. Process modelling allowed to understand how kinetic energy during hits is converted into heat in powder and it’s enable to define a HVC processability criterion. This processability criterion rests on the strainability of powder place in a die during a hit. It has to be sufficient to the dissipated energy in material allows his melting in less than one hundred impacts. This criterion allows to understand why the polyoxymethylene is hard to mold by HVC.

The present thesis entitled “Design and Synthesis of Novel Soft Composites from Physical Gels and Nanomaterials” deals with soft materials derived from low molecular weight gels and nanomaterials. Chapter 1 gives a general introduction and overview of the low molecular weight gel (LMOG) which forms the basis of the work. It delves with the history of research in physical gel field, design of different types of gelator molecules, their interesting self-assembly patterns, potential applications of these gelator molecules as well as challenges to design new gelator molecules. It also encompasses the relatively recent area of two component gel system to conveniently bypass the cumbersome synthetic protocol. The aspect of liquid crystallinity in the gel phase is also discussed to throw light on the pattern of assembly and potential uses of these materials. Towards the end there is a comprehensive discussion on the smart nanocomposites derived from LMOGs and nanomaterials. The design, synthesis and numerous applications of inorganic-organic hybrid composites are discussed. Chapter 2A describes the synthesis and characterization of a variety of fatty acid amides of different naturally occurring L-amino acids whose molecular structures are shown in Chart 2A.1. Some of them were found to form gels with various hydrocarbons. The gelation properties of these compounds were studied by a number of physical methods including FT-IR spectroscopy, X-ray diffraction, scanning electron microscopy (SEM), differential scanning calorimetry, rheology and it was found that gelation was critically dependent on the fatty acid chain length and nature of the amino acid. Among them, L-alanine based gelators were found to be the most efficient and versatile as they self-assemble into a layered structure to form the gel network. Mechanisms for the assembly and formation of gels from these molecules are discussed. (Structural formula) Chart 2A.1. Molecular structures of various fatty acid amides of different amino acids. Chapter 2B describes efficient gelation of both aliphatic and aromatic hydrocarbon solvents by a fatty acid amide, n-lauroyl-L-alanine (Chapter 2B.1). In addition, this compound was found to gelate the binary solvent mixtures comprised of aromatic hydrocarbon e.g. toluene and aliphatic hydrocarbon e.g. n-heptane. SEM and AFM showed that the fiber thickness of the gel assembly increases progressively in the binary mixture of n-heptane and toluene with increasing percentage of toluene. The self- Chart 2B.1. Molecular structure of the gelator. assembly patterns of the gels in individual solvents, n-heptane and toluene are however, different. The toluene gel consists of predominantly one type of morphological species while n-heptane gel has more than one species leading to polymorphic nature of the gel. The n-heptane gel is thermally more stable than the toluene gel as evident from the measurement using differential scanning calorimetry. The thermal stability of the gels prepared in the binary mixture of n-heptane and toluene is dependent on the composition of solvent mixture. Rheology of the gels shows that they are shear-thinning material and show characteristic behavior of soft viscoelastic solids. For the gels prepared from binary solvent mixture of toluene and n-heptane, with incorporation of more toluene in the binary mixture, the gel becomes a more viscoelastic solid. The time sweep rheology experiment demonstrates that the gel made in n-heptane has faster gel formation kinetics than that prepared in toluene. Chapter 2C describes lyotropic mesophase formation by organogels of different fatty acid amides of L-alanine in aromatic solvents. The helical assembly, characteristic of the cholesteric mesophase was found to exhibit reflection bands in circular dichroism spectra. The reflection bands corresponded to the pitch of the helical arrangement of the gelator molecules in the aromatic solvent. Transmission Electron Microscopy (TEM) showed presence of twist in the gel fibres. Polarising optical microscopy of the organogel exhibited weak birefringence confirming lyotropic nature of the assembly. Chapter 3 deals with synthesis and characterization of a new class of molecules with molecular structures shown in Chart 3.1. Among a variety of amino acid based molecules only alanine and serine based molecules were found to form translucent gels in aliphatic hydrocarbons such as n-heptane. TEM showed presence of fiber like structures for alanine whereas serine based gelator produces unique network like structures. SEM of the dried gels exhibited presence of three dimensional fibrous networks to spongy globular cauliflower like structures depending on the molecular structure of the gelators. Rheological studies of the organogels showed that they behave like typical LMOG gels. The oscillatory rheological studies demonstrated that the L-serine based gelator, 5 formed more viscoelastic solid like gel than that of L-alanine based gelator, 1 in n-heptane. Chart 3.1. Molecular structures of different amino acid derivatives from 3,4,5-tri-dodecyloxybenzoic acid scaffold. Chapter 4A presents design and properties of new nanocomposites from LMOG and metal nanoparticles (Chart 4A.1). The profound influence of nanoparticle (NP) incorporation into physical gels was evident from various microscopic and bulk properties. The interaction of nanoparticles with the gelator assembly was found to depend critically on the capping agent coating the nanoparticles. TEM showed long range Chart 4A.1. Molecular structures of the gelator and various AuNPs synthesized. directional assembly of the certain AuNPs along the gel fibers. SEM of the dried gels and nanocomposites indicated that the morphological transformation in the composite microstructures depended profoundly on the capping agent of the nanoparticle. Differential Scanning Calorimetry showed that gel formation from sol postponed to lower temperature with incorporation of AuNPs having capping agents which were able to interact with the gel fibers. Rheological studies indicated that the gel-nanoparticle composites exhibit greater rigidity as compared to the naked gel only when the capping agents were able to interdigitate into the gelator assembly. Also, very low percentage of the AuNPs incorporation could switch the cholesteric mesophase of gel assembly, as evident from circular dichroism. We have been able to define a relationship between materials and molecular properties via manipulation of the molecular structures of NP capping agents. Chapter 4B discusses the design and preparation of novel organogel-carbon nanotube composites by incorporation of single-walled carbon nanotubes (SWNT) into physical gels formed by an L-alanine based Low Molecular Mass Organogelator (Chart 4B.1). The gelation process and the properties of the resulting nanocomposites were found to depend on the kind of SWNTs incorporated in the gels. With pristine SWNTs, only a limited amount could be dispersed in the organogels. Attempted incorporation of higher amounts of pristine SWNTs led to precipitation from the gel. To improve their solubility in the gel matrix, a variety of SWNTs functionalized with different aliphatic and aromatic chains were synthesized (Chart 4B.1). Scanning electron microscope images of the nanocomposites showed that the texture and organization of the gel aggregates were altered upon incorporation of SWNTs. The microstructures of nanocomposites were found to depend on the kind of SWNTs used. Incorporation of functionalized SWNTs into the organogels depressed the sol to gel transition temperature, with the n-hexadecyl chain functionalized SWNTs being more effective than the n-dodecyl chain functionalized counterpart. Rheological investigations of pristine SWNT containing gels indicated that the flow of nanocomposites became resistant to applied stress at a very low wt-% of SWNT incorporation. Again, more effective control of flow behavior was achieved with functionalized SWNTs possessing longer hydrocarbon chains. This happens presumably via effective interdigitation of the pendant chains with the fatty acid amides of L-alanine in the gel assembly. Also, the helical cholesteric mesophase formed by the toluene gel could be switched to a layer stacked assembly by doping functional SWNT. Remarkably, by using a near IR laser irradiation at 1064 nm for a short duration (1 min) at room temperature, it was possible to selectively induce a gel-to-sol phase transition of the nanocomposites, while prolonged irradiation (30 min) of the organogel under identical conditions did not cause gel melting. Chart 4B.1. Molecular structures of the gelator and different functionalized SWNT synthesized. Chapter 5A presents design of two component hydrogels and their potential utilization as a template for metal nanoparticle synthesis. Among a variety of acids and amines (Chart 5A.1) only stearic acid or eicosanoic acid when mixed with di- or oligomeric amines in specific molar ratios form stable gels in water. The formation of such hydrogels depends on the hydrophobicity of the fatty acid, and also on the type of amine used. The gelation properties of these two component systems were investigated using electron microscopy, FTIR, 1H NMR spectroscopy, differential scanning calorimetry (DSC) and both single crystal and cast film X-ray diffraction. FTIR spectral analysis suggests salt formation during gelation. 1H NMR of the gels indicates that the fatty acid chains are immobilized in the gel state and when the gel is melted, these chains regain their mobility. Analysis of DSC data indicates that increase in spacer length in the di-/oligomeric amine lowers the gel melting temperature. Two of these gelator salts developed into crystals and structural details of such systems could be secured by single-crystal X-ray diffraction analysis. The structural information of the salts thus obtained was compared with the XRD data of the self-supporting films of those gels. Such analyses provided pertinent structural insight on the supramolecular interactions that prevail within these gelator assemblies. From the crystal structure it is confirmed that the multilayered lamellar aggregates exist in the gel and it also showed that only one plane of symmetry is present in the gel state. Finally, the hydrogel was used as a medium for the synthesis of silver nanoparticles. The nanoparticles were found to position themselves on the fibers and produce a long ordered assembly of gel-nanoparticle composite (Figure 5A.1). Chart 5A.1. Structures and abbreviations of different acids and amines checked for gelation. Figure 5A.1. TEM images of gel-Ag-NP composite. (a) Ag-NP synthesized in hydrogel of SA-IBPA (1:3.5), (b) Magnified images of Ag-NP preferentially residing on gel fibers. Chapter 5B demonstrates the aptitude of supramolecular hydrogel formation using simple bile acids e.g. lithocholic acid (LCA) in aqueous solution containing di- or oligomeric amines (Chart 5B.1). By variation of the choice of the amines in such mixture the hydrogelation properties could be modulated. However, replacement of LCA by cholic acid or deoxycholic acid resulted in no hydrogelation. FT-IR studies show that the carboxylate and ammonium residues of the two components are primarily involved in salt formation. This promotes further assembly of the components reinforced by continuous Chart 5B.1. Structures and abbreviations of different bile acids and amines checked for gelation. hydrogen bonded network leading to gelation. Electron microscopy shows that the morphology of the gels of two component systems which also depends strongly on the amine part. Variation of amine component from the simple ethanediamine (EDA) to oligomeric amine with lithocholic acid changes the morphology of the assembly from long one dimensional nanotubes to three dimensional complex structures. Single crystal X-ray diffraction analysis with one of the amine-LCA complexes suggested the motif of fiber formation where the amines participate with the carboxylate and hydroxyl moiety through H-bonding and electrostatic forces. The rheological properties of this class of two component system provide clear evidence that this system is a shear-sensitive hydrogel and the flow behavior can be modulated varying the acid-amine ratio. From small angle neutron scattering study, it becomes clear that loose gel from LCA-EDA shows scattering oscillation due to the presence of non interacting nanotubules while for gels of LCA with oligomeric amine the individual fibers come together to form complex three dimensional structures of higher length scale.(For structural formula pl refer the pdf file)

It is widely known that early estimates about the binding properties of drug candidates are important in the drug discovery process. Surface plasmon resonance (SPR) biosensors have become a standard tool for characterizing interactions between a great variety of biomolecules and it offers a unique opportunity to study binding activity. The aim of this project was to develop a SPR based assay for pre-screening of low molecular weight (LMW) drug compounds, to enable filtering away disturbing compounds when interacting with drugs. The interaction between 47 LMW compounds and biological ligands were investigated using the instrument BiacoreTM, which is based on SPR-technology.

In recent years, a compound N-nitrosodimethylamine (NDMA), a probable human carcinogen, has been identified as an emerging disinfection by-product (DBP) since its formation and detection were linked to chlorine-based disinfection processes in several water utilities in the U.S. and Canada. Numerous organic nitrogen compounds present in water may impact the formation of NDMA during disinfection. Amine-based water treatment polymers used as coagulants and flocculants have been suggested as potential NDMA precursors due to the presence of amine functional groups in their structures, as well as the possible presence of dimethylamine (DMA) residues in polymer products. To minimize the potential risk of NDMA associated with water treatment polymers, the mechanisms of how the polymers behave as NDMA precursors and their contribution to the overall NDMA formation under actual water treatment conditions need to be elucidated. This research involved a systematic investigation to determine whether amine-based water treatment polymers contribute to NDMA formation under drinking water and wastewater treatment conditions, to probe the involved reaction mechanisms, and to develop strategies to minimize the polymers NDMA formation potential. The investigation included five research tasks: (1) General screening of NDMA formation potential of commonly used amine-based water treatment polymers, (2) NDMA formation from amine-based water treatment polymers under relevant water treatment conditions, (3) Probing the mechanisms of NDMA formation from polyamine and PolyDADMAC, (4) Effect of water treatment processes on NDMA formation from amine-based water treatment polymers, and (5) Developing strategies to reduce polymers NDMA formation potential. Direct chloramination or chlorination of high doses of polymers in deionized water at longer than typical contact time was used in the general screening of the NDMA formation potential of water treatment polymers and in the studies to identify reaction mechanisms. On the other hand, realistic dosages of chloramines and polymers and contact time were used in simulating representative water treatment conditions to evaluate the contribution of polymers to the overall NDMA formation in real systems. On the basis of the study results, strategies were developed to reduce the NDMA formation potential of amine-based water treatment polymers, which include modification of polymer structures and treatment parameters.

Anaemia, which is caused by iron deficiency, is a global nutritional disorder of utmost concern. It has been assumed that meat, which contains haem as well as non-haem iron, enhances non-haem iron absorption due to the presence of the “meat factor”. In the experiment reported here, 24 semi-anaemic, 3-week-old piglets were utilised as human nutrition models to assess the effects of dietary lactoferrin, meat and LSF (Low Molecular Weight Sarcoplasmic Fraction) on iron bioavailability during a 4-week feeding period. The parameters that were used as measurements of iron bioavailability were changes in haematological indices, haemoglobin iron repletion efficiency, intestinal morphology and mineral balances. Non-significant (p > 0.05) dietary effects were observed for growth performance and for all the haematological and some histological parameters (small intestine villi height, crypt depth and mucosal thickness). Haemoglobin iron repletion efficiency was highest for the control group and was not significantly different between the other 3 diets. The superiority of the control diet in this respect was not consistent with previous trials and can not be explained. Results suggested that increased retention of calcium, magnesium, phosphorous and manganese tended to inhibit iron absorption. However, the LSF and meat diets significantly (p = 0.003) increased the number of goblet cells/100 µm suggesting that mucin secretion was favoured by these two diets. Additionally, all immunological parameters were significantly (p < 0.05) improved by the LSF diet. As such, the LSF diet can be a potential immunobooster feed ingredient for weanling piglets. Overall, the level of LSF in the LSF diet was insufficient to exert a desirable enhancement of iron bioavailability and betterment of 3 iron status of the semi-anaemic piglets relative to the control group. However, the diet containing LSF was as effective as the meat diet with respect to these characteristics.

No description available.

This thesis was about thrombomebolic disease in pregnancy. The incidence of venous thromboembolism (VTE) probably increases 2- to 4-fold when a woman becomes pregnant. I looked on this problem from many aspects. I looked on health care from her gynaecologist and eventually hematologist, recognition her VTE risk, laboratory tests and her medication. I looked on effectivity of medication too.

Made available in DSpace on 2016-06-02T19:29:50Z (GMT). No. of bitstreams: 1 TeseSPG.pdf: 896184 bytes, checksum: 0237c1553b20f09b9264cf38e782d113 (MD5) Previous issue date: 2004-06-30 / The influence of phytoplankton and their excreted materials in natural waters have been considered important issues among metal speciation studies. This work focused on the potential influence of the high molecular weight materials excreted by dominant phytoplankton species of Barra Bonita reservoir (Anabaena spiroides, Microcystis aeruginosa and Aulacoseira granulata) in the speciation and complexation of Cu and Cd. Therefore, this study comprised field and laboratory studies. Seasonal samplings were made during a period of two years in the reservoir. The total, ionic and organic concentrations of Cu and Cd were determined, as well as the complexation parameters with ligands present in the reservoir water. Also, the dissolved organic carbon and physico-chemical parameters of the water column were obtained. A speciation model was applied to metal complexation parameters and total metal concentrations obtained in field investigations. Laboratory cultures of the selected microalgae were made to obtain high molecular weight excreted materials. In a similar manner, the high molecular weight materials were isolated from the reservoir water. These materials were analysed for metal complexation with Cu and Cd, monosaccharide composition and elemental analysis (C, H, N and S). In the reservoir water, Cd speciation was dominated by ionic species, while Cu was mostly associated to the dissolved organic matter. Seasonal samplings presented Cu ligands with similar complexation parameters for the entire period studied. Cd complexation was not detected in the reservoir water. The speciation model resulted in similar Cu2+ concentration to the mean value obtained in field analyses, and indicated higher Cu association to the ligands of the reservoir water. Cu was complexed by all high molecular weight materials studied, while Cd was complexed solely by the cyanophyte materials. Higher proportions of acid monosaccharides in the high molecular weight materials corresponded to higher Cu and Cd complexation parameters, whereas no relation between C, H, N and S proportions and metal complexation properties of the high molecular weight materials was observed. The excreted materials of dominant microalgae from Barra Bonita reservoir had Cu ligands with intermediate to weak binding strength, as those present in the reservoir water. These results indicate the potential influence of such organic materials in metal speciation, bioavailability and mobility of metals with similar behaviour to that of Cu in the reservoir water. / A influência do fitoplâncton e de seus produtos excretados resultantes da fotossíntese em corpos d'água têm sido o enfoque de vários trabalhos que investigam a especiação e o destino de metais. Este estudo teve como hipótese a potencial influência dos materiais de alta massa molecular excretados por três espécies fitoplanctônicas (Anabaena spiroides, Microcystis aeruginosa e Aulacoseira granulata), dominantes no reservatório de Barra Bonita, em relação à especiação e complexação dos metais Cu e Cd na água do reservatório. Para tanto o estudo foi dividido em investigações de campo e experimentos de laboratório. Coletas sazonais por um período de dois anos no reservatório foram avaliadas quanto às espécies dissolvidas totais, orgânicas e iônicas de Cu e Cd, a determinação dos parâmetros de complexação destes metais com ligantes presentes na água, assim como o conteúdo de carbono orgânico dissolvido e os parâmetros físico-químicos da coluna d água. Uma modelagem da especiação química dos metais estudados foi feita com o uso das concentrações totais e os parâmetros de complexação adquiridos nas coletas sazonais. No laboratório foram obtidos os materiais de alta massa molecular excretados em cultivos das microalgas selecionadas, e o material de alta massa molecular dissolvido na água do reservatório, isolado seguindo-se o mesmo procedimento usado para os excretados algais. Estes materiais foram analisados quanto aos parâmetros de complexação com Cu e Cd, e composição monossacarídica e elementar (C, H, N e S). A especiação do Cd na água do reservatório foi dominada por formas iônicas, enquanto o Cu estava em grande maioria associado à matéria orgânica dissolvida. A água do reservatório apresentou, nas coletas sazonais, ligantes para Cu com parâmetros de complexação semelhantes em todo o período estudado. Nas condições experimentais empregadas, não foi detectada a complexação de Cd com ligantes oriundos da água do reservatório. A modelagem da especiação de Cu resultou em uma concentração semelhante de Cu2+ àquela medida em amostras de campo, e maior associação do Cu aos ligantes caracterizados neste estudo. O Cu foi complexado tanto pelos materiais de alta massa molecular das microalgas como também pela água do reservatório, enquanto o Cd foi complexado somente pelo material excretado pelas cianofíceas. Maiores proporções de monossacarídeos ácidos nos materiais corresponderam a parâmetros de complexação de Cu e Cd com valores mais elevados. No entanto, não foi observada uma relação entre as proporções de C, H, N e S e a complexação dos metais. Os excretados das microalgas dominantes no reservatório apresentaram ligantes para Cu com força de associação de intermediária a fraca, assim como os ligantes presentes no reservatório. Estes resultados confirmam o potencial de influência dos excretados na especiação, mobilidade e destino de metais com comportamento semelhante ao Cu, no reservatório de Barra Bonita.