Submitted by Jos? Henrique Henrique (jose.neves@ufvjm.edu.br) on 2017-09-21T19:51:20Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) tarciane_silva_pinto.pdf: 4051834 bytes, checksum: d6525c9152e47311a8695bf3eed5c6e6 (MD5) / Approved for entry into archive by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br) on 2017-10-09T13:37:54Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) tarciane_silva_pinto.pdf: 4051834 bytes, checksum: d6525c9152e47311a8695bf3eed5c6e6 (MD5) / Made available in DSpace on 2017-10-09T13:37:54Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) tarciane_silva_pinto.pdf: 4051834 bytes, checksum: d6525c9152e47311a8695bf3eed5c6e6 (MD5) Previous issue date: 2017 / Neste trabalho, Carbon Dots (CDs) obtidos a partir de celulose de algod?o e contendo 4,5 mmol.g-1 de grupos funcionais ?cidos, dos quais 63 % exibiam pKas t?picos de ?cidos carbox?licos foram usados na prepara??o de filmes automontados com os biopol?meros quitosana (QT) e col?geno (CL) a fim de verificar a morfologia, espessura e intera??es moleculares entre os componentes. A quitosana usada apresentou um total de 4,2 mmolg-1 de grupos funcionais -NH2, correspondente a um grau de desacetila??o de ~70 %. Por outro lado, o col?geno hidrolisado apresentou diferentes grupos funcionais com acidez de Br?nsted, t?picos da presen?a de diferentes amino?cidos na estrutura. Todos os filmes finos foram preparados com a t?cnica de deposi??o camada por camada (do ingl?s: Layer-by-layer (LbL)) por meio de imers?o do substrato nas diferentes solu??es. Os materiais foram caracterizados por diferentes t?cnicas, incluindo Microscopia de For?a At?mica, Espectroscopia na regi?o do UV-Vis, Espectroscopia de Resson?ncia de Plasma de Superf?cie e Titula??o Calorim?trica. Em todas as condi??es experimentais utilizadas para o crescimento dos filmes, observou-se um crescimento linear da quantidade de material depositado com o n?mero de imers?es realizadas. No entanto, diferentes condi??es das solu??es dos biopol?meros e da suspens?o de Carbon Dots produziram filmes com espessura e morfologia diferentes. Nos filmes de QT/CDs a quantidade de nanopart?culas depositadas por bicamada, com solu??o de quitosana em pH = 3,5, pH = 5 e pH = 3,5 na presen?a de 0,1 mol/L de NaCl, foram, respectivamente, 11 mg.m-2, 16 mg.m-2 e 24 mg.m-2 sendo as espessuras dos filmes, com 20 bicamadas, correspondentes a estas quantidades foram de 60, 150 e 200 nm. Este resultado ? atribu?do ao aumento da flexibilidade das cadeias polim?ricas dos biopol?meros, as quais est?o menos carregadas. Dessa forma, as cadeias podem apresentar conforma??es mais adequadas para recobrir eficientemente a estrutura das nanopart?culas quase esf?ricas. Al?m disso, o aumento da for?a i?nica da solu??o de Carbon Dots tamb?m contribui para o aumento de material depositado devido ? forma??o de aglomerados sob estas condi??es. Nos filmes de CL/CDs, a quantidade de nanopart?culas depositadas, com solu??o de col?geno em pH = 3,16, pH = 5 e pH = 3,16 na presen?a de 0,1 mol/L de NaCl, foram 2,3 mg.m-2, 6,46 mg.m-2 e 6,41 mg.m-2, respectivamente. No entanto, a energia de intera??o, obtida por calorimetria isot?rmica, ? maior em pH baixo. Em geral, a quantidade de material depositado nos filmes de col?geno ? bem inferior ?s observadas para os filmes de QT/CDs e, consequentemente, filmes com espessuras entre 40 e 50 nm. Al?m disso, n?o foi observada varia??o significativa entre as massas depositadas nestes filmes com o aumento do pH e for?a i?nica. Estes resultados podem estar relacionados ? menor ?carga parcial positiva? sobre as cadeias da prote?na em rela??o a quitosana, observada pelos potenciais zeta nestas condi??es. Por fim, os resultados aqui apresentados sugerem que as estruturas dos filmes, isto ?, morfologia e espessura, podem ser facilmente controladas e reproduzidas manipulando-se as condi??es das solu??es dos biopol?meros, al?m do tradicional n?mero de imers?es. Em adi??o, o estudo pode contribuir para o desenvolvimento de uma nova classe de dispositivos de alto desempenho, como sensores e superf?cies fotoativas. / Disserta??o (Mestrado) ? Programa de P?s-Gradua??o em Qu?mica, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2017. / In the present work, Carbon Dots (CDs), obtained from cotton cellulose and containing 4.5 mmol g-1 of acid functional groups, of which 63% exhibited typical pKa?s compared to carboxylic acids, were used in the preparation of self-assembled films with the biopolymers Chitosan (QT) and Collagen (CL) in order to verify the morphology, thickness and molecular interactions among the components. The chitosan used in this work had a total of 4.2 mmol g-1 of functional groups ?NH2, corresponding to a deacetylation degree of ~70%. On the other hand, the hydrolyzed collagen showed different functional groups with Br?nsted acidity typical to the presence of different amino acids in the structure. All the thin films were prepared using the Layer-by-layer method (LbL) by immersing the substrate in different solutions. The materials were characterized by several techniques, such as Atomic Force Microscopy, UV-Vis Spectroscopy, Surface Plasmon Resonance and Calorimetric Titration. It was observed, in all experimental conditions for the growth of the films, a linear increase in the amount of deposited material with the number of immersions performed. However, different conditions of the biopolymer solutions produced films with different thickness and morphology. In the films QT/CDs the amount of nanoparticles deposited per bilayer, with the chitosan solution at pH = 3.5, pH = 5 and pH = 3.5 with the presence of 0.1 mol L-1 of NaCl, were, respectively, 11 mg m-2, 16 mg m-2 and 24 mg m-2 with the thickness of the film, at 20 bilayers, at 60, 150 and 200 nm. This result is associated to the increase in the flexibility of the polymeric chains of the biopolymers, which are less charged. Thus, the chains can present conformations that are proper to cover more efficiently the structure of the almost spherical nanoparticles. Furthermore, the increase of the ionic strength of the Carbon Dots solution also contributes to the increase of the material deposited due to the formation of agglomerates in these conditions. In the films CL/CDs, the amount of nanoparticles deposited, with the collagen solution at pH = 3.16, pH = 5 and pH3.16 in the presence of 0.1 mol L-1 of NaCl, were 2.3 mg m-2, 6.46 mg m-2 and 6.41 mg m-2, respectively. However, the interaction energy, obtained by isothermal calorimetry, is higher in low pH. In general, the amount of material deposited on the collagen films is much lower than that observed for the QT/CDs films and, consequently, films thickness are 40 and 50 nm. Besides that, it was not observed any significant variation between the masses deposited in these films with the increase of the pH and the ionic strength. These results may be associated to the lower ?partial positive charge? on the protein chains in relation to the chitosan, observed by the zeta potentials in these conditions. The presented results suggest that the structures of the films, i.e. morphology and thickness, can be easily controlled and reproduced manipulating the conditions of the biopolymer solutions and the number of immersions. Additionally, the study may contribute to the development of a new class of high performance devices, such as sensors and photoactive surfaces.

A técnica de automontagem [Self-Assembly (SA)] tem sido largamente empregada na fabricação de estruturas supramoleculares de polímeros condutores que requerem controle molecular. O paradigma implícito no método de automontagem é a adsorção espontânea de camadas carregadas com cargas opostas, conduzindo assim a um filme de multicamadas formado pela alternância de policátions e poliânions. Nesta dissertação, são empregados dois tipos de polímeros conjugados e seus derivados que são identificados por suas famílias, que são a da polianilina (PAn) e a do poli(pfenileno vinileno) (PPV). São enfatizados os processos de adsorção para as polianilinas e precursores do PPV, propondo-se um mecanismo de adsorção não autolimitada sustentado por condições de não equilíbrio. O processo não autolimitado comprova que a adsorção pode ser controlada por outras interações que não a eletrostática, como as pontes de hidrogênio que são comuns nas polianilinas, e/ou por interações típicas de dispersões coloidais, visto que os polímeros se agregam em solução. Este novo método pode ter grande impacto na fabricação de estruturas supramoleculares porque podem ser obtidos filmes espessos de uma única camada com controle em nível molecular. A desvantagem deste método está na obtenção de filmes não uniformes, propriedade que ainda não é adequadamente controlada. A investigação da formação de filmes de múltiplas camadas e dos processos de fluorescência para filmes de bicamadas e não autolimitados é apresentada e discutida em função dos trabalhos da literatura. Finalmente, são correlacionados os processos de adsorção e a fluorescência / The self-assembly (SA) technique has been widely used for producing supramolecular structures fi-om conducting polymers, in which molecular control may be achieved. The paradigm implicit in the SA method is the spontaneous adsorption of oppositely charged layers, thus leading to a multilayer film containing polycations alternated with polyanions. In this dissertation, two types of polymer are employed in the fabrication of SA films, namely polyanilines and poly(p-phenylene vinylenes) (PPVs). For the polyanilines, emphasis was placed in the adsorption processes, where it is proposed that a non-self-limiting process may be achieved if adsorption is carried out under non-equilibrium conditions. A non-self-limiting process is proof that adsorption is not entirely controlled by electrostatic interactions, but may also depend on H-bonding which is very efficient in polyanilines and on interactions typical of colloid dispersions as the polymers aggregate while in solution. This nove1 method may have a large impact in the fabrication of supramolecular structures because much thicker films may be obtained in a single layer. The disadvantage of this method, however, lies in the fabrication of non-uniform films which cannot be controlled adequately. The investigation of the fabrication of multilayers and of fluorescence processes in films built with bilayers and via non-self-limiting adsorption is presented and discussed in terms of work published in the literature. Finally, the processes of adsorption and fluorescence are correlated

No description available.

No description available.

No description available.

No description available.

Natural composites like wood are scale-integrated structures that range from molecular to the macroscopic scale. Inspired by this design, layer-by-layer (LbL) deposition technique was used to create lignocellulosic composites from isolated wood polymers namely cellulose and lignin, with a lamellar architecture. In the first phase of the study, adsorption of alkali lignin onto cationic surfaces was investigated using a quartz crystal microbalance with dissipation monitoring (QCM-D). Complete coverage of the cationic surface with alkali lignin occured at low solution concentration; large affinity coefficients were calculated for this system at differing pH levels. Adsorption studies with organosolv lignin in an organic solvent, and spectroscopic analysis of mixtures of cationic polymer with alkali lignin revealed a non-covalent interaction. The work demonstrated how noncovalent interactions could be exploited to molecular organize thin polyphenolic biopolymers on cationic surfaces. The second phase of the study examined the adsorption steps during the LbL assembly process to create novel lignocellulosic composites. LbL assembly was carried out using oxidized nanocellulose (NC) and lignin, along with a cationic polymer poly(diallyldimethylammonium chloride) (PDDA). QCM-D was used to follow the sequential adsorption process of the three different polymers. Two viscoelastic models, namely Johannsmann and Voigt, were respectively used to calculate the areal mass and thickness of the adsorbed layers. Atomic force microscopy studies showed a complete coverage of the surface with lignin in all the disposition cycles, however, surface coverage with NC was seen to increase with the number of layers. Free-standing composite films were obtained when the LbL process was carried out for 250 deposition cycles (500 bilayers) on a cellulose acetate substrate, following the dissolution of the substrate in acetone. Scanning electron microscopy of the cryo-fractured cross-sections showed a lamellar structure, and the thickness per adsorption cycle was estimated to be 17 nm. The third phase of the study investigated the effect of LbL ordering of the polymers versus a cast film composed of a blended mixture of the polymers, using dynamic mechanical analysis. A tan ï ¤ peak was observed in the 30 – 40 ºC region for both films, which was observed in the neat NC film. Heating of the samples under a compressive force produced opposite effects in the films, as the LbL films exhibited swelling, whereas the cast films showed densification. The apparent activation energy of this transition (65 – 80 kJ mol-1) in cast films, calculated based on the Arrhenius equation was found to be coincident to those reported for the ï ¢ transition of amorphous cellulose. The peak was seen to disappear in case of LbL films in the second heat, whereas it was recurring in case of cast films of the blended mixture, and neat NC films. Altogether, the together the work details a novel path to integrate an organized lignin and cellulose molecular structure, albeit modified from their native form, into a three-dimensional composite material. / Ph. D.

This thesis presents applications of the layer-by-layer (LbL) assembly technique in fabrication of thin films with a primary focus on design and development of electrochromic devices. The optical properties of electrochromic materials change as they alter between redox states. The morphology and properties of LbL-assembled thin films can be modified by varying several processing factors such as dipping duration, ion type, ion concentration, pH, molecular weight, and ionic strength. In the present work, several factors of LbL assembly process were manipulated to tailor electrochromic thin films of desired attributes. An electrochromic device (ECD) with fast optical switching speed was designed and constructed based on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). This device exhibited optical switching speeds of 31 and 6 ms for coloration and decoloration respectively, on a 60 mm2 area. Poly(aniline 2-sulfonic acid) (PASA) is a relatively new ionic polymer, and its electrochromic properties have not been previously investigated in much detail. PASA thin film showed several redox states corresponding to color changes from dark blue to gray as it passed different redox states. One particularly interesting and promising design for ECDs is dual electrochrome. Dual electrochrome ECDs based on PANI and polyaniline (PASA) are investigated in this thesis. The PANI/PASA thin film showed superior spectroelectrochemical properties compare to other ECDs reported here or elsewhere. An electrode with single wall carbon nanotubes (SWCNTs) coating was tested as the substrate for an ECD based on poly[2-(3-thienyl) ethoxy-4-butylsulfonate] (PTEBS) to examine performance of the electrochromic polymer on a substrate other than an indium tin oxide (ITO) electrode. Compared to ITO, the SWCNT based device exhibited superior properties. / Master of Science

A quantitative understanding of thermal field evolution is vital for quality control in additive manufacturing (AM). Because of the unknown material parameters, high computational costs, and imperfect understanding of the underlying science, physically-based approaches alone are insufficient for component-scale thermal field prediction. Here, I present a new framework that integrates physically-based and data-driven approaches with quasi in situ thermal imaging to address this problem. The framework consists of (i) thermal modeling using 3D finite element analysis (FEA), (ii) surrogate modeling using functional Gaussian process, and (iii) Bayesian calibration using the thermal imaging data. Based on heat transfer laws, I first investigate the transient thermal behavior during AM using 3D FEA. A functional Gaussian process-based surrogate model is then constructed to reduce the computational costs from the high-fidelity, physically-based model. I finally employ a Bayesian calibration method, which incorporates the surrogate model and thermal measurements, to enable layer-to-layer thermal field prediction across the whole component. A case study on fused deposition modeling is conducted for components with 7 to 16 layers. The cross-validation results show that the proposed framework allows for accurate and fast thermal field prediction for components with different process settings and geometric designs. / Master of Science / This paper aims to achieve the layer to layer temperature monitoring and consequently predict the temperature distribution for any new freeform geometry. An engineering statistical synergistic model is proposed to integrate the pure statistical methods and finite element modeling (FEM), which is physically meaningful as well as accurate for temperature prediction. Besides, this proposed synergistic model contains geometry information, which can be applied to any freeform geometry. This paper serves to enable a holistic cyber physical systems-based approach for the additive manufacturing (AM) not only restricted in fused deposition modeling (FDM) process but also can be extended to powder-based process like laser engineered net shaping (LENS) and selective laser sintering (SLS). This paper as well as the scheduled future works will make it affordable for customized AM including customized geometries and materials, which will greatly accelerate the transition from rapid prototyping to rapid manufacturing. This article demonstrates a first evaluation of engineering statistical synergistic model in AM technology, which gives a perspective on future researches about online quality monitoring and control of AM based data fusion principles.

Dans ce travail, nous démontrons que la technique de dépôt multicouche dite layer by layer (LbL) est une technique polyvalente où les propriétés des multicouches telles que l'épaisseur, la charge et la densité peuvent être facilement contrôlées par le choix des polyélectrolytes (PE), le nombre d'étapes et les conditions de dépôt (pH, force ionique, etc.). Nous démontrons que des multicouches de PE faible (PAH / PAA) peuvent être utilisées pour fournir une double fonction aux membranes (PEM) en tant que couche de séparation NF et comme revêtement sacrificiel permettant un nettoyage facile de la membrane. Ces membranes à base de PEM montrent des performances de rejet des solutés dans une gamme typique des membranes NF, c'est-à-dire rejetant peu les ions monovalents (NaCl) (<24%), tout en rejetant> 60% de l'ion divalent SO42- et la molécule organique neutre sulfaméthoxazole (SMX). Par un rinçage et un lavage à contre-courant à basse pression avec une solution stimuli appropriée, nous obtenons un nettoyage sacrificiel réussi d'une membrane colmatée, ce qui ramène la résistance d'une membrane colmatée à celle de la membrane vierge. Après un nouveau dépôt sur la membrane avec le même système PEM, la résistance de la membrane est égale à la résistance du PEM d'origine, ce qui démontre la réutilisation de cette approche. Le mécanisme de rejet des membranes étudiées s'est révélé principalement déterminé par l'exclusion stérique mais aussi par l'exclusion de Donnan. Nous avons étudié notre système PEM pour préparer des membranes pour des applications de nanofiltration résistant aux solvants (SRNF). Des membranes de SRNF avec une couche de séparation de PEM ont été préparées sur un support UF de polyacrylonitrile hydrolysé (PAN-H). Les résultats de cette étude montrent une manière simple et polyvalente d'utiliser le pH pendant le revêtement pour régler les performances de la membrane pour une application SRNF spécifique. Afin d'amener l'approche PEM et du nettoyage sacrificiel à leur maturité et de modifier des modules existants, nous avons simplifié la procédure LbL pour des membranes fibres creuses en utilisant un "dépôt dynamique" ou un "dépôt actif" qui consiste à rincer les solutions du PE à travers le canal interne de la membrane fibre creuse. Cette méthode de dépôt avec sa reproductibilité et son homogénéité permet de revêtir les modules de membrane UF existants. / In this work, we demonstrate that layer by layer (LbL) is a versatile technique where control over multilayer properties such as thickness, charge and density, can be easily achieved simply by the choice of polyelectrolytes, number of coating steps and coating conditions (pH, ionic strength etc.). We demonstrate that multilayers of weak PEs (PAH/PAA) can be used to provide a dual function to membranes (PEM) i.e., as NF separation layer and as a sacrificial coating that allows easy membrane cleaning. These PEM based membranes, shows rejection performance of solutes in a range typical for NF membranes i.e., hardly rejecting monovalent ions (NaCl) (<24%), while rejecting > 60% of the divalent ion SO42- and the neutral organic molecule sulfamethoxazole (SMX). By a rinse and a low pressure backwash with a suitable trigger solution, we obtain a successful sacrificial cleaning of a fouled membrane, bringing the resistance of a fouled membrane back to that of the pristine membrane. Recoating the clean membrane support with the same PEM system brings the resistance of the coated membrane equal to the resistance of the original PEM, demonstrating the re-usability of this approach. The rejection mechanism of the investigated membranes was found to be mainly determined by size exclusion, but influenced by Donnan exclusion. We investigated our weak PEM system to prepare membranes for solvent resistant nanofiltration (SRNF) applications. SRNF membranes with PEM separation layer were prepared on a UF hydrolyzed polyacrylonitrile (PAN-H) support by the LbL method. Results of this study show a simple and versatile way of using pH during coating to tune membrane performance for specific SRNF application. To bring PEM coating and sacrificial cleaning approach into maturity and to coat existing modules we present the simplification of the LbL procedure for hollow fibre membranes by employing "dynamic coating" or "active coating" which involves flushing the PE's solutions through the lumen of the hollow fibre membrane. This coating method with its reproducibility and homogeneity has the potential to coat existing UF membrane modules.