Biblioteca Digital

This paper presents the results of experiments carried out in a laboratory-scale photochemical reactor on the photodegradation of different polymers in aqueous solutions by the photo-Fenton process. Solutions of three polymers, polyethyleneglicol (PEG), polyacrylamide (PAM), and polyvinylpyrrolidone(PVP), were tested under different. conditions. The reaction progress was evaluated by sampling and analyzing the total organic carbon concentration in solution (TOC) along the reaction time. The behavior of the different polymers is discussed, based oil the evolution of the TOC-time curves. Under specific reaction conditions, the formation and coalescence of solid particles was Visually observed. Solids formation occurred simultaneously to a sharp decrease in the TOC of the liquid phase. This may be favorable for the treatment of industrial wastewater containing polymers, since the photodegradation process can be Coupled with solid separation systems. which may reduce the treatment cost. (C) 2008 Elsevier B.V. All rights reserved.; CAPES (Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior); CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnologico); FAPESP (Fundacao de Amparo Pesquisa do Estado de Sao Paulo)

Observando o atual interesse em polímeros organometálicos para diversas aplicações, foi feita a síntese de uma série de polímeros conjugados contendo ferroceno na cadeia principal visando à investigação de suas propriedades, em especial fenômenos magnetorresistivos, magneto-ópticos e de óxido-redução. Os polímeros preparados pelo método de McMurry foram os seguintes: PFV: poli(1,1'-ferrocenilenovinileno) e PFV-DOPPV-M: poli[1,1'-ferrocenilenovinileno-alt-(2,5-di-n-octilóxi)-1,4-fenilenovinileno]. Outros dois polímeros foram preparados utilizando o método de polimerização de Wittig, o PFV-DOPPV-W: poli[1,1'-ferrocenilenovinileno-alt-(2,5-di-n-octilóxi)-1,4-fenilenovinileno] e o PFV-DMPPV: poli[1,1'-ferrocenileno-vinileno-alt-(2,5-dimetóxi)-1,4-fenilenovinileno]. A síntese de polímeros contendo segmentos π-conjugados equenos e bem definidos separados por segmentos não-conjugados é uma das melhores stratégias para a obtenção de polímeros emissores de luz azul. Com base nesse argumento foi feita a síntese de uma série de polímeros contendo um derivado metoxilado de bisfenol-A (BPA) na cadeia principal, alternando-se com unidades de PPV ou PFV que apresentam segmentos conjugados bem definidos. Os polímeros preparados foram os seguintes: BPA-DOPPV:poli[2...

Neste trabalho, desenvolvemos blendas de polímeros biodegradáveis e polímeros condutores com objetivo de avaliar o potencial destes materiais para uso em aplicações biomédicas. O polímero condutor polipirrol (PPY) e os polímeros biodegradáveis poli(-caprolactona) (PCL) e poli(3-hidróxido de butirato) (P3HB) foram escolhidos devido à comprovada biocompatibilidade apresentada por cada um destes três polímeros. O PPY foi sintetizado via polimerização em emulsão, utilizando-se o dodecil sulfato de sódio (SDS) como surfactante e o FeCl3 como oxidante e dopante. A morfologia do polímero obtido foi estudada por microscopia eletrônica de varredura e por microscopia eletrônica de transmissão. O PPY se apresentou como agregado de partículas aproximadamente esféricas, com dimensões da ordem de 80 a 200nm. Verificamos que ocorre uma redução significativa do tamanho das partículas formadas, proporcionalmente ao aumento da concentração de SDS. Os ensaios de microanálise por energia dispersiva (EDS) e de espectroscopia de absorção no infravermelho (FTIR) demonstraram a incorporação de SDS ao PPY, o SDS atuando como contra-íon deste polímero. Isto está de acordo com os resultados de condutividade elétrica obtidos para o polímero sintetizado sem o SDS (1.9S/cm) e com 100mM de SDS (23.3S/cm). A seguir...

O projeto consistiu em avaliar o emprego de polímeros catiônicos e aniônicos de diferentes pesos moleculares como auxiliares de filtração no tratamento de águas de abastecimento proveniente de mananciais com alto grau de eutrofização com vistas a possibilitar a otimização da remoção de material particulado e minimização da evolução da perda de carga. O aparato experimental é composto, principalmente, por 4 filtros em escala piloto de alta taxa do tipo camada profunda e fluxo descendente por gravidade operados em paralelo. Os filtros possuem 5 m de altura e diâmetro interno de 150 mm. O procedimento experimental foi dividido em três etapas, execução de ensaios de fluidificação e expansão do leito dos filtros e utilização de polímeros catiônicos e de polímero aniônico como auxiliares de filtração. A primeira etapa teve como objetivo definir parâmetros de dimensionamento do sistema de lavagem em contra-corrente com ar e água e nas duas etapas seguintes foram realizados os ensaios de filtração a uma taxa de 500 m³/m²/dia, com a utilização dos polímeros com três dosagens diferentes. Os polímeros utilizados foram CA-2577, CA-2581, CD-2592 e N1986. Estes possuem estrutura e pesos moleculares variáveis...

Modelling polymers with side chains is always a challenge once the degrees of freedom are very high. In this study, we present a successful methodology to model poly[2-methoxy-5-(2′-ethyl-hexyloxy)-p-phenylenevinylene] (MEH-PPV) and poly[3-hexylthiophene] (P3HT) in solutions, taking into account the influence of side chains on the polymer conformation. Molecular dynamics and semi-empirical quantum mechanical methods were used for structure optimisation and evaluation of optical properties. The methodology allows to describe structural and optical characteristics of the polymers in a satisfactory way, as well as to evaluate some usual simplifications adopted for modelling these systems. Effective conjugation lengths of 8-14.6 and 21 monomers were obtained for MEH-PPV and P3HT, respectively, in accordance with experimental findings. In addition, anti/syn conformations of these polymers could be predicted based on intrinsic interactions of the lateral branches. © 2013 Copyright Taylor and Francis Group, LLC.

Two different cationic polymers of the same chemical type and with very similar chemical structures were reacted with a natural bentonite over a wide range of polymer/clay ratios. This study involved the synthesis of cationic aliphatic ammonium polyionenes, specifically 3,6-ionene and 3,6-dodecylionene. Ionenes are ion-containing polymers that contain quaternary nitrogen atoms in the main macromolecular chain as opposed to a pendant chain. The CHN content, basal spacing, and elemental composition of each of the polymer-clay complexes were analyzed by X-ray diffraction, X-ray fluorescence, and thermogravimetry. All the polycations reacted to form interlayer complexes with clay, which displaced more Na+ and little Ca2+. Sodium and calcium were both present as interlayer cations in the clay and its complexes. The TG/DTG curves show that both polymers underwent thermal degradation in more than one stage. Specifically, 3,6-ionene was found to undergo two stages of decomposition and 3,6-dodecylionene undergo three stages. The behavior of the TG/DTG curves and the activation energy values suggest that 3,6-dodecylionene (E = 174,85 kJ mol-1) complexes have greater thermal stability than 3,6-ionene (E = 115,52 kJ mol-1) complexes. The mechanism of degradation suggests a direct interaction with the dodecyl chain containing 12 carbons...

A indústria em geral e particularmente o segmento plástico enfrentam uma época de competitividade global e acirrada. Além disso, pressões sociais como a questão ambiental, eficiência energética e busca por produtos de qualidade são fatores que impulsionam a demanda por inovações e aprimoramentos constantes. Dentro do mercado dos polímeros, os plásticos de engenharia representam a fatia de materiais com melhor potencial para estes aprimoramentos. É objetivo deste trabalho avaliar as principais tendências de melhoria de propriedades, novas tecnologias de modificação e reforços, novas aplicações potenciais e volumes de consumo para os representantes dessa classe de materiais para os próximos 20 a 30 anos. O primeiro material selecionado para este estudo foi o Nylon 66, devido à sua grande versatilidade de modificação e aplicação além de ser um dos principais representantes dos polímeros de engenharia. O polipropileno também foi selecionado devido à sua grande versatilidade e possibilidade de utilização em aplicações de engenharia, especialmente na forma de compostos. A técnica de prospecção tecnológica utilizada foi o método Delphi que se baseia em um questionário enviado a especialistas da área em rodadas consecutivas para a obtenção de um consenso. O anonimato dos participantes...

Este trabalho consistiu no desenvolvimento e caracterização de materiais para aplicação em células fotovoltaicas híbridas. No Capítulo I, uma introdução geral sobre o funcionamento e estado da arte de células solares, e sobre as propriedades de polímeros condutores e nanopartículas inorgâncias é apresentada. O Capítulo II contém os objetivos deste trabalho. No Capítulo III, foram investigados novos polímeros condutores, baseados na combinação de unidades fluoreno com unidades tiofeno e/ou benzeno. As propriedades fotofísicas, eletroquímicas e de transporte de cargas foram caracterizadas, e esses polímeros foram então combinados com um derivado solúvel de fulereno (PCBM) e os compósitos formados (heterojunção) foram aplicados em células solares com configuração ITO | PEDOT:PSS | Heterojunção | LiF | Al. A seguir, foram sintetizadas nanopartículas de CdSe com diferentes tamanhos, usando um método descrito na literatura. Essas partículas foram caracterizadas por medidas de absorção e emissão, voltametria cíclica (VC), difração de Raios-X (DRX) e microscopia eletrônica de transmissão (TEM), conforme apresentado no Capítulo IV. Os polímeros investigados inicialmente foram combinados com as nanopartículas de CdSe...

The cytokine network is one of the major controlling systems of the inflammatory process, driving the magnitude and duration of the host response against invading microorganisms, foreign materials, or altered internal stimuli. Pro- and antiinflammatory cytokines were quantified after in vitro culture of a mixed population of monocytes/macrophages and lymphocytes with biodegradable polymers. Different blends of starch-based polymers and their composites filled with hydroxyapatite were studied and compared with poly-L-lactide. Interleukin (IL)-1, IL-6, and tumour necrosis factor- were investigated as the markers of immunological reactivity because they are known to act at the early stages of injury/invasion. Interferon-, recognized as a proinflammatory cytokine, although not present during early responses was also investigated. Contrarily, IL-4 derived from T lymphocytes, was investigated because it is an immunoregulator that counteracts some aspects of inflammation. T lymphocyte activation was also determined by quantifying IL-2. The results support the hypothesis that different biodegradable polymers can affect mononuclear cell activation and the production of several cytokines associated with the inflammatory process. No IL-2 or interferon- was found in the culture supernatants after 3...

Dissertação de mestrado integrado em Engenharia Civil; A diminuição das reservas de combustíveis fósseis e a crescente preocupação com a redução do consumo de energia e de emissões de carbono tem conduzido ao desenvolvimento de novas tecnologias, nomeadamente no âmbito das vias de comunicação. Deste modo surgiram novos tipos de misturas betuminosas com o intuito de se tornarem mais vantajosas a nível ambiental, mas também mais económicas do que as que se vinham produzindo. Assim, o presente trabalho têm como objetivo de estudo a modificação de betumes utilizando polímeros reciclados e avaliar as propriedades elementares e reológicas do mesmo. Os polímeros utilizados para alterar o betume foram o polietileno de alta densidade (PEAD) e o etileno e acetato de vinilo (EVA). No trabalho efetuado realizou-se modificações apenas com um polímero isolado e também um sistema misto com os dois polímeros Numa primeira fase estudou-se quais as percentagens ótimas de polímero a introduzir no betume de forma a obter o melhor comportamento elementar e reológico do betume. Seguidamente, após a caracterização do ligante partiu-se para a formulação das misturas betuminosas, incluindo o estudo da composição granulométrica e das condições de produção da mistura. Por fim realizou-se a caracterização das misturas betuminosas efetuadas através dos ensaios de sensibilidade à água...

Environmental Laws and Regulations to dump wastewater are increasingly relevant and, together with pressure from environmentalists, provide awareness of academics in search of solutions. In Brazil, federal law, through Resolution No. 357 of 17/03/05 of the National Environmental Council - CONAMA, in Article 24 deals with the disposal of these effluents. Water pollution with heavy metals is concern because of the difficulty of the treatment and removal from the environment. Copper, for example, is a metallic element and in the form of salt is very soluble in water which dificults its removal. In this context, this study aims to evaluate the extraction of copper with acrylamide polymers through the process of assisted flocculation followed by filtration. Therefore, we used acrylamide polymers, produced by SNF Floerger, with varying degrees of ionicity which is the parameter examined on the extraction of copper. We used the FA polymers FA 920 SH, AH 912 SH, AN 905 SH, AN 910 SH, AN 923 SH, AN 945 SH, AN 956 SH and AN 977 SH, which have anionicities different from each other and growing in that order. The parameters temperature, pH, concentration of the copper solution and stirring speed are fixed. The polymer solution was added to a solution of 200 ppm copper...

The aim of this PhD thesis work has been the synthesis of novel antimicrobial amphiphilic polymers to prevent microbial biofilm related-infections and counteract microbial resistance onset. In fact, microbial biofilms are difficultly eradicable due to their high antibiotic resistance. To reach this purpose different strategies along this work were exploited.

The high transmittance of polymers in the terahertz (THz) frequency range is certainly the main reason for the pronounced interest this class of materials receives from the community. Polymers are commonly applied as base material for optical components, sample carriers, or simply test samples, in most fields of THz spectroscopy and imaging. On the other hand, polymers offer an important opportunity for demonstrating the potential of THz technologies as versatile tool for analytical investigations. In this paper, we summarize some recent technical advances underlining the suitability of THz spectroscopy and imaging for material characterization and contact-free testing. The absorption coefficient and refractive index of several biodegradable polymers before and after aging in water are reported. Furthermore, the influence of additive agglomeration in elastomers complements the evaluation of this review of the analytical potential of THz technologies with respect to polymers.; Bernd M. Fischer, Steffen Wietzke, Marco Reuter, Ole Peters, Ralf Gente, Christian Jansen, Nico Vieweg, and Martin Koch

Anorganisch-organische Hybridpolymere auf Siloxanbasis werden als Trägermatrizen für katalytisch aktive Übergangsmetallkomplexe eingesetzt. Dabei sind vor allem Eigenschaften wie die Quellfähigkeit in verschiedenen Lösungsmitteln und die Beweglichkeiten von Molekülfragmenten der trockenen, sowie der suspendierten Polymere interessant. Im ersten Teil der vorliegenden Dissertation wird die Untersuchung der Mobilitäten neuer anorganisch-organischer Hybridpolymere mit Hilfe dynamischer Methoden der Festkörper- und der Suspensions-NMR-Spektroskopie behandelt. Dabei werden die Ergebnisse der Mobilitätsstudien mit dem Verknüpfungsgrad der Polymere korreliert. Im zweiten Teil dieser Arbeit werden NMR-spektroskopisch ermittelte dynamische Parameter (Relaxationszeiten) einer großen Zahl anorganisch-organischer Hybridpolymere mit Hilfe eines künstlichen Neuronalen Netzwerkes (Kohonen-Karte) analysiert. Dabei wird versucht Ähnlichkeiten und Gegensätze im dynamischen Verhalten der unterschiedlichen Polymere mit ihrer Struktur zu korrelieren. Ziel ist die einfachere Vorhersagbarkeit dynamischer Eigenschaften und eine Vereinfachung der Synthese neuer Hybridpolymere.; Inorganic-organic siloxane-based hybrid polymers serve as supporting matrices for catalytically active transition metal complexes. Their properties like swelling abilities in different solvents and the mobilities in the dry as well as the suspended state are of interest. The first part of this thesis deals with the investigation of the mobilities of new inorganic-organic hybrid polymers by means of dynamic methods of solid state and suspension state NMR spectroscopy. The results of these mobility studies are correlated with the cross-linkage of the investigated polymers. In the second part of this thesis NMR-spectroscopic derived dynamic parameters (relaxation times) of a large number of inorganic-organic hybrid polymers are analysed by an artificial neural network (Kohonen-map). An attempt to correlate similarities and contrasts in the dynamic behaviour of the different hybrid polymers with their structural features is made. Easier predictions of dynamic properties and simpler syntheses of new hybrid polymers are the aim of this study.

This work presented in this dissertation aims to understand physical and chemical properties of bottlebrush polymers and determine their potential for applications including for anti-fouling surfaces and for reduction in oil-water interfacial tension. This dissertation focus on the following four parts: the synthesis of well-defined bottlebrush polymers and investigation of stimuli-responsive film properties; analysis of the solution phase behaviors and conformation of bottlebrush polymers with thermally-responsive side chains; the behavior of bottlebrush polymers in blends with linear polymers; and the development of bottlebrush polymers for antifouling surfaces and for reducing the oil-water interfacial tension. In chapter 1, we provide an introduction to bottlebrush polymers. Details on the synthesis, conformation, phase behavior, potential applications, and recent work with bottlebrush polymers are discussed. Chapter 2 describes the preparation of stimuli-responsive bottlebrush thin films with hydrophobic polystyrene (PS) and hydrophilic poly(ethylene oxide) (PEO) amphiphilic side-chains. We find that due to the conformational flexibility of the polymeric side-chains, bottlebrush polymer films exhibit a processing dependent contact angle. This behavior is analogous to that observed for polymer brush films and enables a more scalable approach to responsive...

Two-phase partitioning bioreactors (TPPBs) are a bioprocessing tool that limits inhibition of cell growth by toxic compounds in bioreactors by utilizing an immiscible secondary phase to sequester compounds that inhibit microbial cell growth. Early TPPBs used organic solvents as the sequestering phase despite challenges identifying solvents that were inexpensive and biocompatible, although recent efforts have utilized polymers as the sequestering phase in TPPBs. Research on the selection of polymers for use as the sequestering phase in TPPBs has focused on predicting solute uptake by first principles in order to maximize the partitioning coefficient of a target solute. Some research has shown that low molecular weight (MW) polymers have improved partitioning coefficients, although their biocompatibility is in need of further study; this thesis investigates the effect of polymer MW on microbial biocompatibility. Trends in biocompatibility were assessed for polypropylene glycol to Saccharomyces cerevisiae and Pseudomonas putida. Given that log P has been used as an important physiochemical property for predicting biocompatibility, with higher log P values associated with improved biocompatibility, experiments were performed to determine the log P of polymers. Polymers were also water-washed to shift the log P upwards by removing low MW polymer chains. Average log P determination experiments showed that as the polymer MW increased...

The use of polymers in soybean seeds has been accomplished with the purpose of incorporating products like insecticides, fungicides, growing substances, minor fertilizers and so on, in order to improve the visual aspect of the seed, to promote smaller operator's intoxication risk and to provide a better seeds' acting and seedlings after sowing. The main objective of this work was to evaluate the recovered seeds' effects in soybeans seed quality lots of high and low germination of the cv. AG 7000. The seed's film coating was accomplished with two commercial marks of polymers, LABORSAN ® , and LANXESS ® , in doses of 2 and 3,5 ml for each kg with and without mixture of the fungicide Carbendazim + Thiram (firewalk ® ). The seeds' quality evalutions, were measured by the germination test, germination in sand and accelerated aging. The use of polymers in soybean seeds provides seeds with good appearance and coloration and can be applied to differentiate the seed from the commercial grain. The fungicide and the polymers do not affect the physiological quality of soybean seed. The results of the polymers and fungicide were superior in the test of accelerated aging, showing higher germination in relation to the check treatment.; O uso de polímeros em sementes de soja vem sendo realizado com a finalidade de incorporar produtos fitossanitários...

Biodegradable polymers form a unique class of materials that created an entirely new concept when originally proposed as biomaterials. That is, for the first time, a material performing a structural application was designed to be completely resorbed and to become weaker over time. This concept was first applied successfully with catgut sutures and later, with more arguable results, on bone fixation plates and pins. Current research on new and improved biodegradable polymers is focused on more sophisticated biomedical applications to solve patients' problems with higher efficacy and the least possible pain. One example is tissue engineering, in which a biodegradable scaffold seeded with an appropriate cell type provides a substitute for damaged human tissue while the natural process of regeneration is completed. An overview is given of the degradation properties and mechanisms of biodegradable polymers, their processability and biocompatibility, focusing on the aspects most relevant to biomedical applications. The main families of biodegradable polymeric systems are described and the systems that are commercially available or that are currently being studied and proposed for specific medical applications are reviewed.

"Smart" polymers that sense stimuli in aqueous environments and that respond with a pronounced change in their solvation are of great utility in biotechnology and medicine. Currently, however, only few peptide polymers are known to display this behavior. Here, we uncover the syntax -- defined as the arrangement of amino acids (letters) into repeat units (words) that have a functional behavior of interest -- of a novel and extensive family of genetically encoded "smart" peptide polymers, termed syntactomers, that dictates their ability to undergo a soluble to insoluble phase transition at temperatures above a lower critical solution temperature (LCST) or below an upper critical solution temperature (UCST). We show that this syntax ranges from phase transition polymers composed of simple repeats of a few amino acids to polymers whose syntax resembles the complex sequence of peptide drugs and protein domains that exhibit dual levels of function, as seen by their stimulus responsiveness and biological activity. This seamless fusion of materials and protein design embodied by syntactomers promises, we hope, a new generation of designer polymers with multiple levels of embedded functionality that should lead to new functional materials of broad interest

; Dissertation

Ion imprinted nano-magnetic composite polymers for selective removal of hexavalent uranium were prepared by a precipitation polymerization technique in the presence of γ-methacryloxypropyltrimethoxysilane (γ-MPS) coated magnetite and other pre-polymerization reagents. The synthesized magnetic polymers were then leached with NaHCO3 to produce magnetic ion imprinted polymers (IIPs) with fabricated adsorption sites complementary to the uranyl ions in terms of size and shape. Several parameters were investigated to obtain conditions which gave the optimum adsorption of the uranyl onto the magnetic IIPs and their corresponding controls, magnetic ion non-imprinted polymers (NIPs). The optimum amount of magnetic sorbent, initial concentration and contact time were 50 mg, 2.5 mg L-1 and 45 min, respectively. The adsorption capacity of the magnetic IIP (1.15 ± 0.01 mg g-1) was higher than that of the magnetic NIP (0.93 ± 0.02 mg g-1). This indicated that the former had a somewhat higher affinity for U(VI) than the later. The magnetic polymers also displayed good selectivity of the order: U(VI) > Ni(II) > Mg(II). After six cycles of use, the magnetic polymers illustrated good stability and reusability.