abstract: Polymer fibers have broad applications in wearable electronics, bulletproof vests, batteries, fuel cells, filters, electrodes, conductive wires, and biomedical materials. Polymer fibers display light density and flexibility but are mostly weak and compliant. The ceramic, metallic, and carbon nanoparticles have been frequently included in polymers for fabricating continuous, durable, and functional composite fibers. Nanoparticles display large specific areas, low defect density and can transfer their superior properties to polymer matrices. The main focus of this thesis is to design, fabricate and characterize the polymer/nanocarbon composite fibers with unique microstructures and improved mechanical/thermal performance. The dispersions and morphologies of graphene nanoplatelets (GNPs), the interactions with polyvinyl alcohol (PVA) molecules and their influences on fiber properties are studied. The fibers were fabricated using a dry-jet wet spinning method with engineered spinneret design. Three different structured fibers were fabricated, namely, one-phase polymer fiber (1-phase), two-phase core-shell composite fiber (2-phase), and three-phase co-axial composite fiber (3-phase). These polymer or composite fibers were processed at three stages with drawing temperatures of 100˚C, 150˚C, and 200˚C. Different techniques including the mechanical tester, wide-angle X-Ray diffraction (WAXD), scanning electron microscope (SEM), thermogravimetric analysis (TGA), and differential scanning calorimeter (DSC) have been used to characterize the fiber microstructures and properties. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2018

Trimesoyl chloride (TMC) crosslinked poly(vinyl alcohol) (PVA) / chitosan (CS) membranes and synthetic polyimide membranes were prepared for pervaporation dehydration of isopropanol and gas separation. PVA membranes were interfacially crosslinked with different amounts of TMC/hexane, and the degree of crosslinking was characterized by Fourier Transform Infrared Spectroscopy - Attenuated Total Reflectance Spectroscopy (FTIR-ATR) and water uptake. The asymmetric structure of the PVA-TMC membranes was revealed by FTIR-ATR. Thermal analysis was performed to understand the pyrolysis mechanism, which was supposed to be a combination of elimination of water and/or trimesic acid followed by breakage of the main chain. Water permeation and pervaporation dehydration of isopropanol were conducted, and the results showed that PVA-3TMC had the best overall pervaporation properties among the four PVA-TMC membranes studied. Sorption properties and pervaporation behavior of the PVA-3TMC membrane were investigated. The effects of water/isopropanol on the polymer matrix and the possible change of the degree of crystallinity induced by the sorbed water were believed to account for the sorption properties. For water permeation and pervaporation dehydration of isopropanol in a heating-cooling cycle, the permeation flux did not change significantly, and the selectivity was improved by the formation of crystallites during the heating run. For pervaporation in the diluting and concentrating runs at 60 °C, there was no change in the membrane permeability. Chitosan membranes were interfacially crosslinked in TMC/hexane with different crosslinking time. The membrane with a higher degree of crosslinking showed a higher degree of swelling in water at room temperature. A two-stage thermal decomposition mechanism was proposed based on thermal analyses. Pure gas permeation was performed with CO2 and N2 at room temperature, and CS-TMC-2 showed the best performance, with a CO2 permeability of ~163 Barrer and a CO2/N2 permeability ratio of ~42. Pervaporation was carried out for dehydration of isopropanol with the unconditioned and conditioned membranes, and the CS-TMC-3 membrane showed the best pervaporation performance. Pervaporation and gas separation properties were affected by the crosslinking-induced relaxation and the mobility/packing properties of the CS-TMC matrices. 4,4'-(Hexafluoroisopropylidene) diphthalic anhydride (6FDA)-based and 2,2-bis[4-(3,4-dicarboxyphenoxy) phenyl]propane dianhydride (BPADA)-based copolyimides were synthesized from one-step high-temperature polymerization in m-cresol. Polymers were characterized with Gel Permeation Chromatography (GPC), FTIR, Nuclear Magnetic Resonance Spectroscopy (NMR), Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). Surface free energies and interfacial free energies were calculated from contact angles to characterize hydrophilicity of the polyimide membranes. Gas permeation properties of 6FDA-based copolyimide membranes were studied with N2, O2, H2, He and CO2, and pervaporation dehydration of isopropanol was performed with 6FDA-based and BPADA-based membranes. An empirical linear moiety contribution approach was proposed, and the moiety contribution factors were used to illustrate the effects of dianhydrides and diamines on permselectivities of the copolyimide membranes. Bulky side groups, flexibility of polymer main chains, structures of monomer moieties, and interactions between gas molecules and polymer chains were shown to affect gas permselectivities, while in pervaporation, both sorption and diffusion properties were affected by the interactions between penetrants and polymer matrices as well as the steric effects of monomer moieties.

Trimesoyl chloride (TMC) crosslinked poly(vinyl alcohol) (PVA) / chitosan (CS) membranes and synthetic polyimide membranes were prepared for pervaporation dehydration of isopropanol and gas separation. PVA membranes were interfacially crosslinked with different amounts of TMC/hexane, and the degree of crosslinking was characterized by Fourier Transform Infrared Spectroscopy - Attenuated Total Reflectance Spectroscopy (FTIR-ATR) and water uptake. The asymmetric structure of the PVA-TMC membranes was revealed by FTIR-ATR. Thermal analysis was performed to understand the pyrolysis mechanism, which was supposed to be a combination of elimination of water and/or trimesic acid followed by breakage of the main chain. Water permeation and pervaporation dehydration of isopropanol were conducted, and the results showed that PVA-3TMC had the best overall pervaporation properties among the four PVA-TMC membranes studied. Sorption properties and pervaporation behavior of the PVA-3TMC membrane were investigated. The effects of water/isopropanol on the polymer matrix and the possible change of the degree of crystallinity induced by the sorbed water were believed to account for the sorption properties. For water permeation and pervaporation dehydration of isopropanol in a heating-cooling cycle, the permeation flux did not change significantly, and the selectivity was improved by the formation of crystallites during the heating run. For pervaporation in the diluting and concentrating runs at 60 °C, there was no change in the membrane permeability. Chitosan membranes were interfacially crosslinked in TMC/hexane with different crosslinking time. The membrane with a higher degree of crosslinking showed a higher degree of swelling in water at room temperature. A two-stage thermal decomposition mechanism was proposed based on thermal analyses. Pure gas permeation was performed with CO2 and N2 at room temperature, and CS-TMC-2 showed the best performance, with a CO2 permeability of ~163 Barrer and a CO2/N2 permeability ratio of ~42. Pervaporation was carried out for dehydration of isopropanol with the unconditioned and conditioned membranes, and the CS-TMC-3 membrane showed the best pervaporation performance. Pervaporation and gas separation properties were affected by the crosslinking-induced relaxation and the mobility/packing properties of the CS-TMC matrices. 4,4'-(Hexafluoroisopropylidene) diphthalic anhydride (6FDA)-based and 2,2-bis[4-(3,4-dicarboxyphenoxy) phenyl]propane dianhydride (BPADA)-based copolyimides were synthesized from one-step high-temperature polymerization in m-cresol. Polymers were characterized with Gel Permeation Chromatography (GPC), FTIR, Nuclear Magnetic Resonance Spectroscopy (NMR), Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). Surface free energies and interfacial free energies were calculated from contact angles to characterize hydrophilicity of the polyimide membranes. Gas permeation properties of 6FDA-based copolyimide membranes were studied with N2, O2, H2, He and CO2, and pervaporation dehydration of isopropanol was performed with 6FDA-based and BPADA-based membranes. An empirical linear moiety contribution approach was proposed, and the moiety contribution factors were used to illustrate the effects of dianhydrides and diamines on permselectivities of the copolyimide membranes. Bulky side groups, flexibility of polymer main chains, structures of monomer moieties, and interactions between gas molecules and polymer chains were shown to affect gas permselectivities, while in pervaporation, both sorption and diffusion properties were affected by the interactions between penetrants and polymer matrices as well as the steric effects of monomer moieties.

Orientadora: Profa. Dra. Christiane Bertachini Lombello / Coorientadora: Profa. Dra. Ana Paula Romani / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Biomédica, São Bernardo do Campo, 2018. / Neste trabalho foi avaliado o potencial uso em engenharia de tecidos de blendas de quitosana (QTS) e poli(álcool vinílico) (PVOH). O objetivo deste trabalho foi avaliar se uma blenda polimérica composta por QTS/PVOH (3:1) mantém esse potencial. Foram analisadas amostras das matérias-primas, ou seja, os polímeros puros de QTS e PVOH, além da blenda de QTS/PVOH (3:1) não reticulada, a blenda reticulada com 1% e com 5% m/m de glutaraldeído e a blenda reticulada com 1% e 5% m/m de glioxal. Foram realizadas medidas da rugosidade superficial e de degradação em condições fisiológicas por 14 dias. As medições da rugosidade superficial mostraram que, de modo geral as blendas possuem uma maior variação de rugosidade, enquanto que os polímeros puros são mais homogêneos. Entretanto, a rugosidade superficial não influenciou de maneira significativa a viabilidade e adesão celular. A reticulação com o glutaraldeído parece provocar um atraso na degradação dos filmes em condições fisiológicas. Não era desejado que houvesse a presença dos agentes reticulantes na forma livre nos filmes devido à sua toxicidade. Através das espectroscopias de FTIR e FT-Raman não foi observada a presença destes agentes. As avaliações biológicas foram feitas por meio de ensaios in vitro de citotoxicidade direta e por extrato, análise da interação de células com os biomateriais com microscópio eletrônico de varredura (MEV). Nos ensaios que envolveram cultura de células foi utilizada a linhagem de células Vero. A avaliação da morfologia celular para citotoxicidade direta não revelou nenhum efeito citotóxico significativo por parte dos biomateriais. O uso da técnica de MTT para avaliação da citotoxicidade por extrato revelou um decréscimo da viabilidade observada nas células em contato com os extratos das blendas reticuladas. A análise por MEV das amostras dos biomateriais na presença de cultura de células indicou que as blendas reticuladas com 1 % de glutaraldeído ou com glioxal possuem um melhor desempenho em relação a adesão e proliferação celular do que as não-reticuladas. Também foi estudada a forma com que as diferentes composições influenciam na adesão celular e a reticulação por glioxal parece atrasar, mas não inibir o processo. Em conclusão, a partir dos resultados obtidos, as blendas de QTS/PVOH apresentam potencial para o uso em engenharia de tecidos, com a reticulada com 1% de glutaraldeído sendo a mais promissora. / At the present work it was sought to assess the potential use in tissue engineer of chitosan (QTS) and poly(vinyl alcohol) (PVOH). Both QTS and PVOH shows advantageous characteristics to their usage as biomaterials intended for tissue engineer, and this work's objective was to evaluate if a polymeric blend composed of QTS/PVOH (3:1) retains this potencial. There were evaluated samples of the original biomaterials, that was the pure QTS and PVOH polymers, as well as the QTS/PVOH blend (3:1), the 1 % and 5 % m/m glutaraldehyde cross-linked blends and the 1 % and 5 % m/m glyoxal cross-linked blends. The superficial rugosity was measured and it was studied the degradation of the films for 14 days. The rugosity variation between the films didn't result in differences of cell adhesion and proliferation. The glutaraldehyde cross-linking slowed down the degradation of the films. It wasn't desired that there were traces of free cross-linking agents, because of their toxicity. With the FTIR and FT-Raman spectroscopy it was observed that there weren't any free cross-linking agents within the films. The biological evaluations were performed by direct and by extracts in vitro cytotoxicity essay, by observation of cell interaction with the biomaterials with scanning electron microscopy (SEM) and by surface roughness. At the essays that involved cell cultures, it was used Vero lineage cells. The direct cytotoxicity were evaluated by cell morphology and didn't reveal any significant cytotoxic effect by the biomaterials. The extract cytotoxicity showed a decrease of cell viability with the cross-linked blends extracts, but it was uncertain if this is due a cytotoxic effect or other factor. The samples SEM analysis showed that the 1 % glutaraldehyde cross-linked blend and the glyoxal cross-linked blends provided a more suitable surface for cell adhesion and proliferation than the non cross-linked ones. The surface roughness measurements revealed that, in general, the blends have more roughness variation along their surface, while the pure polymers show a more homogeneous surface. However, the surface roughness didn't influence in a significant way the cell viability. In conclusion, from the present results, the QTS/PVOH blends exhibit potencial for tissue.

Com a alta taxa de desertificação dos solos e a necessidade de irrigação constante dos plantios, existe a necessidade da criação de um polímero superabsorvente (SAP) com a característica de ser biodegradável. Observando o estágio tecnológico relacionado às atividades de pesquisa e desenvolvimento de SAPs no Brasil, foi utilizado o poli (álcool vinílico)/PVA e o amido de mandioca para a formação de hidrogéis a partir de blendas poliméricas. Assim, soluções aquosas desses polímeros foram reticuladas quimicamente, usando o glutaraldeído como agente reticulante e comparadas com amostras reticuladas por radiação gama, irradiadas a uma dose de 25 kgy. Os hidrogéis resultantes foram caracterizados por diversas técnicas analíticas como a fração gel, o intumescimento em água destilada, a espectroscopia de infravermelho com refletância total atenuada ATR (FT-IR), a termogravimetria (TG/DTG), a calorimetria exploratória diferencial (DSC) e a microscopia eletrônica de varredura (MEV). Observou-se uma maior reticulação nos hidrogéis reticulados com o glutaraldeído e em consequência um menor grau de intumescimento quando comparadas com as amostras que foram irradiadas. Com vias a produzir hidrogéis em uma escala industrial, misturas de PVA e amido foram processadas por extrusão reativa, mudando assim o processo de preparação de solução aquosa para misturas secas. Foram extrudadas amostras de PVA com diferentes pesos moleculares tais como o PVA 26-88, o PVA 40-88, o PVA 110-99 e o poli (ácido glioxílico vinílico)/PVGA, este último sintetizado a partir da modificação do PVA 110-99. Foi adicionado na mistura o ácido glioxílico no desenvolvimento do SAP por reticulação química nas amostras do PVA, por ter grupos carboxílicos que podem aumentar o intumescimento e também servir como agente reticulante. Também foram feitas formulações de extrusão sem o ácido glioxílico para serem usados como brancos. Adicionou-se nas misturas diversos agentes plastificantes como a glicerina e o polietilenoglicol (PEG 400) e as propriedades mecânicas foram estudadas. Foram desenvolvidas duas análises fatoriais de 23 para analisar as mudanças na reticulação das formulações. Os pellets foram caracterizados com as mesmas técnicas analíticas que os hidrogéis feitos em solução, adicionando-se análises de intumescimento e reversibilidade de intumescimento em diversos solventes como a água pura, a água da chuva, as soluções tampão de pH 3, pH 7 e pH 10, além de soro fisiológico, visando a aplicação em diferentes solos com diferentes pH e salinidades. Os testes de intumescimento em diferentes sais demonstraram a ter menor retenção de água quando comparada com água pura. Os testes de reversibilidade de intumescimento dos pellets mostraram que a maioria das formulações perde a sua capacidade de intumescimento máximo aos seis primeiros ciclos. Foi feita a compressão dos pellets para observar a flexibilidade dos mesmos, visando aplicações debaixo do solo. Realizou-se um estudo de biodegradação em terra ao longo de 120 dias, e estudou-se a relação direta com os valores da fração gel. Os resultados mostraram que os pellets menos reticulados intumesceram mais, enquanto as microscopias mostraram que essas amostras tinham uma morfologia mais porosa, o que contribuiu na melhora na retenção do líquido. Além disso, eram mais flexíveis e biodegradaram mais rápido, sendo extremamente viáveis para a aplicação na agricultura. Foi verificado que o PVA 40-88 apresentou os melhores valores de intumescimento em diferentes sais. Com o SAP obtido, foi constatado que a extrusão reativa é um método viável para a produção dos SAPs. / With high soil desertification rate and the need for constant irrigation of the plantations, there is the need to create a superabsorbent polymer (SAP) with the characteristic of being biodegradable. Noting the technological stage related to research and development activities of SAPs in Brazil, we used poly (vinyl alcohol)/PVA and cassava starch for the formation of hydrogels from polymer blends. Thus, aqueous solutions of these polymers were chemically crosslinked using glutaraldehyde as crosslinking agent and compared to samples cross-linked by gamma irradiation, irradiated the a dose of 25 kgy. The resulting hydrogels were characterized by various analytical techniques such as gel fraction, swelling in distilled water, infrared spectroscopy with attenuated total reflectance (ATR-FTIR), thermogravimetry (TG/DTG), the differential scanning calorimetry (DSC) and the scanning electron microscopy (SEM). There was a higher crosslink in the hydrogels crosslinked with glutaraldehyde and consequently a lower degree of swelling as compared to samples that were irradiated. With routes to produce hydrogels on an industrial scale, PVA and starch mixtures were processed by reactive extrusion, thus changing the aqueous solution preparation process to dry mix. PVA samples were extruded with different molecular weights such as PVA 26-88, PVA 40-88, PVA 110-99 and poly (vinyl glyoxylic acid)/PVGA, the latter synthesized from the modified PVA 110-99. It was added to the mixture glyoxylic acid in the SAP development by chemical crosslinking of the PVA sample for having carboxyl groups that may increase the swelling and also serve as crosslinker. Also extrusion formulations were made without the glyoxylic acid to be used as white. Was added to the mixture, various plasticizers such as glycerin and polyethylene glycol (PEG 400) and the mechanical properties were studied. two factor analyzes were developed from 23 to analyze the changes in crosslinking formulations. The pellets were characterized with the same analytical techniques that hydrogels made in solution by adding analyzes swelling and swelling of reversibility in various solvents such as pure water, rain water, pH buffer solutions 3, pH 7 and pH 10, in addition to saline solution, aimed at application in different soils with different salinities and pH. swelling tests at different salts shown to have lower water retention when compared to pure water. The pellets reversibility of the swelling tests showed that most formulations loses its swelling capacity up to the first six cycles. The compression of the pellets was taken to observe their flexibility, targeting applications underground. We conducted a study of biodegradation on land over 120 days, and studied the direct relationship with the gel fraction values. The results showed that the pellets swelled more crosslinked least while microscopy showed that these samples had a more porous morphology, which contributed to the improvement in fluid retention. Moreover, they are more flexible and biodegrade more rapidly and are extremely viable for use in agriculture. It has been found that PVA 40-88 showed better swelling values at different salts. With SAP obtained, it was found that the reactive extrusion is a viable method for the production of SAPs.

Orientador: Marcelo Ganzarolli de Oliveira / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-19T16:07:51Z (GMT). No. of bitstreams: 1 Simoes_MairaMartinsdeSouzaGodoy_D.pdf: 6359705 bytes, checksum: 9fb71ed44e3423b6b245f6b70134e270 (MD5) Previous issue date: 2011 / Resumo: O Poli(álcool vinílico) (PVA) é polímero biocompatível que pode ser usado como matriz para a incorporação de S-nitrosoglutationa (GSNO), que é uma molécula endógena que exerce todas as funções bioquímicas do óxido nítrico (NO). Os principais objetivos deste trabalho foram a obtenção de filmes sólidos de PVA capazes de eluir GSNO localmente, que pudessem ser utilizados para aplicações tópicas e para o recobrimento de stents. Os filmes de PVA foram reticulados fisicamente através de ciclos de congelamento/descongelamento (C/D). Verificou-se que a aplicação de 1 a 5 ciclos C/D leva a um aumento da cristalinidade dos filmes comparada aos filmes não submetidos a C/D. Este efeito está associado ao aumento do raio de giro de estruturas espalhadoras de raios X e com a redução do coeficiente de difusão da GSNO. A liberação tópica de GSNO a partir de filmes de PVA na pele de voluntários levou a um aumento significativo do fluxo sanguíneo dérmico, medido por fluxometria com laser Doppler. Demonstrou-se que a aplicação de ciclos C/D pode ser usada para controlar a velocidade e a intensidade de aumento de fluxo sanguíneo. Filmes de PVA/GSNO aplicados como revestimentos de poços de placas de cultura de células mostraram atividade bactericida dose e tempo-dependentes contra cepas de S. aureus e P. aeruginosa, sendo capazes de esterilizar completamente estas duas bactérias multi-resistentes após 6 h de incubação. Filmes de PVA/GSNO permitiram a obtenção de revestimentos aderentes sobre a superfície de stents intracoronários de aço inox levando a uma redução significativa da adesão plaquetária após incubação com sangue total. Estes resultados permitem propor o uso de filmes de PVA/GSNO fisicamente reticulados para aplicações tópicas no tratamento de lesões infectadas, para promover a vasodilatação de tecidos isquêmicos e para a melhoria das propriedades hemocompatíveis de dispositivos de contato sanguíneo / Abstract: Poly(vinyl alcohol) (PVA) is a biocompatible polymer that can be used as a matrix for incorporation of S-nitrosoglutathione (GSNO), an endogenous molecule that exerts all the biochemical functions of nitric oxide (NO). The main objectives of this work were to obtain solid PVA films capable of releasing GSNO locally, which could be used in topical applications and for the coating for stents. PVA films were physically crosslinked through freezing-thawing cycles (F/T).It was observed that films subjected to 1 to 5 cycles shows higher crystallinity than films not subjected to F/T. This effect is associated with an increase in the gyration radius of the X-ray scattering structures an with a decrease in the GSNO diffusion coefficient. Topical GSNO release from PVA films on the skin of volunteers led to a significant increase of dermal blood flow, measured by laser Doppler flowmetry. It was shown that F/T cycles can be used to control the rate and intensity of blood flow increase. PVA/GSNO films applied as coatings of cell-culture plate wells showed dose and time-dependent bactericidal activities against S. aureus and P. aeruginosa, being able of completely sterilizing these mult-resistant bacteria after 6 h of incubation. PVA/GSNO films allowed the formation of adherent coatings on the surface of intracoronary stainless steel stents, and lead to a significant reduction of platelet adhesion after incubation with whole blood. These results allow suggesting the use of physically crosslinked PVA/GSNO films in topical applications for the treatment of infected lesions, for promoting the vasodilation of ischemic tissues and for improving the hemocompatible properties of blood contact devices / Doutorado / Físico-Química / Doutor em Ciências

Orientador: Marcelo Ganzarolli de Oliveira / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-27T01:47:36Z (GMT). No. of bitstreams: 1 Lourenco_SarahdeMarchi_M.pdf: 4886643 bytes, checksum: 5a7f5c0b7aed7c8f6aea7bd9acf6ae6d (MD5) Previous issue date: 2015 / Resumo: O Óxido nítrico (NO) é uma espécie radicalar endógena que desempenha papéis importantes em diversos processos fisiológicos, incluindo controle do tônus vascular. Desordens microcirculatórias associadas à depleção da produção endógena de NO são as principais causas de doenças isquêmicas e têm demandado o desenvolvimento de biomateriais capazes de liberarem NO localmente em tecidos. O poli(álcool vinílico), PVA, é um polímero hidroxilado biocompatível já utilizado para propósitos médicos que permite modificações químicas através de reações de condensação com ácidos carboxíli cos. Neste trabalho, utilizamos o ácido mercaptosuccínico (AMS) para preparar membranas de PVA reticuladas quimicamente contendo grupos ¿SH (PVA-SH), capazes de serem posteriormente S-nitrosadas e liberarem NO localmente por vias térmica e fotoquímica. O PVA foi esterificado com AMS em meio acidificado com HCl. As membranas foram moldadas por precipitação da solução polimérica através de imersão em acetona, secas por liofilização e, subsequentemente, S-nitrosadas com ácido nitroso. As membranas de PVS-SH apresentaram cristalinidade reduzida e graus de intumescimento maiores que 600% em água. Medidas por quimiluminescência em tempo real mostraram que as membranas S-nitrosadas são capazes de liberar NO termicamente e que a sua irradiação com luz visível aumenta significativamente a taxa de liberação de NO. Foi demonstrado que estas propriedades de liberação de NO levam à vasodilatação após a aplicação tópica das membranas no antebraço de volun tários saudáveis, mostrando sua potencial aplicabilidade para o tratamento tópico de doenças isquêmicas da pele / Abstract: Nitric oxide (NO) is an endogenous radical species, which plays important roles in many physiological processes, including the control of vascular tone. Microcirculatory disorders associated with the depletion of endogenous NO production are the main causes of ischemic diseases and have demanded biomaterials capable of delivering NO locally to tissues. Poly(vinyl alcohol), PVA, is a biocompatible hydroxylated polymer already used for medical purposes that allows chemical modification through condensation reactions with carboxylic acids. In this work, we used mercaptosuccinic acid (MSA) to prepare SH-containing crosslinked PVA membranes (PVA-SH) capable of being further S-nitrosated to release NO locally through thermal and photochemical pathways. PVA was esterified with MSA in aqueous HCl-acidified medium. The membranes were cast by precipitation of the polymeric solutions, through their immersion in acetone, dried by lyophilization and subsequently S-nitrosated with nitrous acid. The PVA-SH membranes displayed a reduced crystallinity and swelling degrees in water higher than 600%. Real time chemiluminescence measurements showed that the S-nitrosated membranes are capable of releasing NO thermally and that their irradiation with visible light increases significantly the rate of NO release. These NO-release properties promoted local vasodilation after topical application of the membranes on the forearm of health volunteers, showing their potential applicability for the topical treatment of ischemic skin diseases / Mestrado / Físico-Química / Mestra em Química

Arterial stiffness is an important biometric in predicting cardiovascular diseases, since mechanical properties serve as indicators of several pathologies such as e.g. atherosclerosis. Shear Wave Elastography (SWE) could serve as a valuable non-invasive diagnostic tool for assessing arterial stiffness, with the technique proven efficient in large homogeneous tissue. However the accuracy within arterial applications is still uncertain, following the lack of proper validation. Therefore, the aim of this study was to assess the accuracy of SWE in arterial phantoms of poly(vinyl alcohol) cryogel by developing an experimental setup with an additional mechanical testing setup as a reference method. The two setups were developed to generate identical stress states on the mounted phantoms, with a combination of axial loads and static intraluminal pressures. The acquired radiofrequency-data was analysed in the frequency domain with retrieved dispersion curves fitted to a Lamb-wave based wave propagation model. The results indicated a significant correlation between SWE and mechanical measurements for the arterial phantoms, with an average relative error of 10 % for elastic shear moduli in the range of 23 to 108 kPa. The performed accuracy quantification implies a satisfactory performance level and as well as a general feasibility of SWE in arterial vessels, indicating the potential of SWE as a future cardiovascular diagnostic tool.

RESUMEN El objetivo de esta tesis fue la obtención y caracterización de films biodegradables con características antimicrobianas y/o antioxidantes a partir de quitosano (CH). Para modular sus propiedades y mejorar su funcionalidad, se estudió la combinación con otras matrices poliméricas: almidón de trigo (WS), polivinil alcohol (PVA) y ácido poliláctico (PLA). Además se incorporaron aceites esenciales (EO) de tomillo (Th) o albahaca (B), ¿-tocoferol (Tp) y ácido cítrico (CA). Se evaluó el efecto del tratamiento de homogenización de las dispersiones formadoras de films (FFD) en films de quitosano con EO en diferentes proporciones. La microfluidización dio lugar a una reducción en el tamaño de gota, a una mayor carga superficial de las mismas y una menor viscosidad de las dispersiones. Además, intensificó todos los efectos provocados por la incorporación de EO sobre las propiedades mecánicas de los films debido a potenciación de las interacciones con el polímero. A baja proporción de EO, la microfluidización mejoró las propiedades de barrera al vapor de agua de los films, pero no tuvo un impacto significativo en la permeabilidad al oxígeno. Los films ejercieron un papel protector frente a la oxidación en grasa de cerdo. La presencia de EO en los films, a pesar de aumentar la permeabilidad al oxígeno, dio lugar a una menor velocidad de oxidación de las muestras (especialmente a alta humedad relativa), probablemente por el efecto antioxidante de los componentes de los EO. Los films de quitosano se mostraron efectivos en el control del deterioro microbiano cuando se aplicaron en carne de cerdo picada, pero la incorporación de los EO no mejoró su actividad antimicrobiana. Se incorporó CH en films de WS en diferentes proporciones. La adición de CH en cantidades crecientes dio lugar a un aumento en la viscosidad y estabilidad de las FFD. Ambos polímeros mostraron un alto grado de compatibilidad lo que dio lugar a una microestructura homogénea. El aumento de la proporción de CH dio lugar a films con mejores propiedades mecánicas ya que el CH pareció inhibir la retrogradación del almidón. Los films WS:CH dieron lugar a una reducción de la carga microbiana cuando se aplicaron en muestras de carne de cerdo picada. Se incorporaron diferentes antioxidantes (aceite esencial de tomillo y albahaca, ácido cítrico y ¿-tocoferol) en films mezcla de WS (80%) y CH (20%). Los films presentaron una microestructura heterogénea por la inmiscibilidad de componentes, principalmente el film con ¿-tocoferol que presentó separación de fases. Esto llevó asociado una superficie más rugosa, con menor brillo y, en el caso del ¿-tocoferol, un color más amarillo. No obstante la incorporación de antioxidantes conllevó un aumento de la transparencia y una disminución de la permeabilidad al oxígeno. El CA provocó un aumento en el módulo de elasticidad y un descenso de la extensibilidad de los films. La incorporación de CH en matrices de PVA dio lugar a films altamente homogéneos, debido a la compatibilidad de ambos polímeros. Se obtuvieron films más resistentes y rígidos, pero menos extensibles. Se observó una reducción del grado de cristalinidad y un aumento de la estabilidad térmica, además de una reducción de la trasmisión de la luz UV. Así mismo, cuando se aplicaron a muestras de carne de cerdo picada presentaron una acción antimicrobiana. La incorporación de CH en una matriz de PLA mediante extrusión no afectó al comportamiento térmico del PLA ni a su grado de cristalinidad. Ambos polímeros se mostraron incompatibles. La reducción del tamaño de las partículas de CH minimizó el impacto negativo sobre las propiedades mecánicas y de barrera al vapor de agua. En su aplicación a muestras de carne de cerdo picada, la presencia de CH mejoró las propiedades antimicrobianas de los films. / Bonilla Lagos, MJ. (2013). Desarrollo de films y recubrimientos comestibles bio-activos como soporte de agentes antioxidantes y antimicrobianos [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/28370

Tesis por compendio / [EN] In the present Doctoral Thesis, different strategies to improve functional properties of starch films for food packaging applications were analysed: study of the effect of amylose:amylopectin ratio, blend with other polymers poly(vinyl alcohol) (PVA), and incorporation of different fillers (rice bran and cellulose nanocrystals-CNCs) and antimicrobial agents (neem oil-N, oregano essential oil-O and silver nanoparticles-AgNPs). Likewise, a biodegradation study of the films as affected by antimicrobials was carried out. Among different starches with distinct amylose:amylopectin ratio, pea starch was selected with higher values of this ratio. The high content of amylose gave rise to stiffer and more resistant to fracture films, with lower oxygen permeability, which decreased during storage. Pea starch-PVA (S-PVA) blend films represented a good strategy to improve film properties without a notable increase in cost. The PVA addition led to films which were less water soluble and not as sensitive to water sorption, more extensible and resistant than neat starch films, while they maintained the high oxygen barrier and provided stability to the matrix during ageing. In this sense, S-PVA ratios near to 1:1 are recommendable. When rice bran with the smallest particle size was used as filler, it improved the elastic modulus of the films, but reduced the film stretchability and barrier properties, due to the enhancement of the water binding capacity and the introduction of discontinuities in the matrix. Incorporation of CNCs into S-PVA films, as a reinforcing material, enhanced phase separation of polymers, did not imply changes in water vapour barrier of the films but improved the film mechanical performance: they became stiffer and more stretchable, while crystallization of PVA was partially inhibited. Silver loaded S-PVA films exhibited antimicrobial activity against the fungi (Aspergillus niger and Penicillium expansum) and bacteria (Listeria innocua and Escherichia coli) genera, depending on the silver concentration. Silver nanoparticles provoked notable changes in the film colour and transparency but no relevant changes in the other physical properties. Silver was completely delivered to aqueous simulants within the firsts 60 minutes of contact, but the film release capacity drastically decreased in the non-polar simulant, where the overall migration limit for food contact packaging materials (60 mg/Kg simulant) was accomplished. So, the use of the developed films as food packaging materials should be restricted to fat-rich foodstuffs. The incorporation of oregano essential oil (O), as antimicrobial agents, into the S-PVA matrix gave rise to active films against bacteria and fungi, whereas films containing neem oil (N) were not effective. Higher O concentration in the films was required to observe antifungal effect with respect to the antibacterial activity. Oils did not notably affect water sensitivity and water barrier properties of the films, but at high ratio, oils implied weaker film networks, affecting their mechanical performance. Blend of starch with PVA significantly improved PVA biodegradation and disintegration behaviour. Incorporation of silver species to S-PVA films slowed down their biodegradation kinetics while increased their degradation ratio. However, no significant effect of O was observed on the biodegradability indices despite the antimicrobial activity detected for this oil. N even promoted biodegradation of S-PVA films. Finally, a food application of biopolymer coatings was studied, using chitosan and essential oils (oregano or rosemary) to prevent weight loss and fungal development of semi-hard goat's milk cheeses. Coating were highly effective at reducing fungal growth and cheese weight loss while slightly reduced lipolytic and proteolytic activities in the cheese. Sensory evaluation revealed that the cheeses double coated with chitosan-oregano oil were the best evaluated in terms of aroma and flavour. / [ES] En la Tesis Doctoral, se han analizado diferentes estrategias para mejorar las propiedades funcionales de películas de almidón para aplicaciones de envasado de alimentos: el estudio del ratio amilosa:amilopectina, mezclas con otros polímeros (alcohol de polivinilo-PVA), y la incorporación de diferentes refuerzos (salvado de arroz y nanocristales de celulose-CNCs) y agentes antimicrobianos (aceite de neem-N, aceite esencial de orégano-O y nanopartículas de plata-AgNPs). También se realizó un estudio de biodegradación de las películas observando el efecto de los antimicrobianos. Entre los diferentes almidones con distinto ratio amilosa:amilopectina, se seleccionó el almidón de guisante con altos valores de amilosa. El alto contenido en amilosa dio lugar a películas más rígidas y resistentes a la fractura, con baja permeabilidad al oxígeno, la cual disminuyó durante el almacenamiento. Las películas de mezcla de almidón-PVA (S-PVA) representaron una buena estrategia para mejorar las propiedades de las películas sin incrementar notablemente el precio. La adición de PVA dio lugar a películas menos solubles en agua, menos sensibles a su absorción y más extensible y resistentes que las de almidón puro, mientras mantuvieron alta barrera al oxígeno y dieron estabilidad a la matriz durante el envejecimiento. Son recomendables los ratios de S-PVA cercanos a 1:1. El salvado de arroz con menor tamaño de partícula, mejoró el modulo elástico de las películas, pero su extensibilidad y propiedades barrera empeoraron debido a la mejor capacidad de retención de agua y a las discontinuidades introducidas. La incorporación de CNCs en las películas de S-PVA incrementó la separación de fases de los polímeros, sin cambios en la permeabilidad al vapor de agua, y mejoró las prestaciones mecánicas: películas más rígidas y extensibles, mientras que inhibió parcialmente la cristalización del PVA. Las películas de S-PVA con partículas de plata exhibieron actividad antimicrobiana contra dos hongos y dos bacterias, dependiendo de la concentración de plata. Las AgNPs provocaron cambios en el color de las películas así como en su transparencia. La plata fue completamente liberada en los primeros 60 minutos en contacto con simulantes acuosos, sin embargo la liberación disminuyó en simulantes no polares, donde se cumple el límite de migración global. Por lo tanto, el uso de las películas desarrolladas para envasado de alimentos debe ser restringido a productos alimenticios ricos en grasas. La incorporación de O en la matriz de S-PVA dio lugar a películas activas contra bacterias y hongos, mientras que las películas con N no fueron efectivas. Se necesitaron concentraciones más altas de O en las películas para observar un efecto antifúngico respecto a la actividad bactericida. Los aceites no afectaron notablemente la sensibilidad ni las propiedades barreras al agua de las películas, aunque la mayor proporción de aceite dio lugar a películas con una red más débil, afectando sus prestaciones mecánicas. La mezcla de S con PVA mejoró significativamente el comportamiento de biodegradación y desintegración de las películas. La incorporación de AgNPs a películas de S-PVA disminuyó su cinética de biodegradación mientras aumentó su ratio de degradación. La adición de O no presentó efecto significativo en el índice de biodegradación a pesar de la actividad antimicrobiana detectada. El N incluso mejoró la biodegradación de las películas. Finalmente, se realizó una aplicación de recubrimientos basados en biopolímeros, usando quitosano-CH y aceite esencial de orégano o romero para evitar la pérdida de peso y el desarrollo de hongos en quesos de cabra semicurados. Los recubrimientos fueron efectivos en la reducción del crecimiento fúngico y la pérdida de peso de los quesos, mientras que la actividad lipolítica y proteolítica ligeramente disminuyó. El análisis sensorial reveló q / [CA] S'han analitzat diferents estratègies per a millorar les propietats funcionals de pel·lícules de midó per a aplicacions d'envasat d'aliments: l'estudi de la ràtio amilosa:amilopectina, mescles amb altres polímers (alcohol polivinílic-PVA), i la incorporació de diferents reforços (segó d'arròs i nanocristalls de celulosa-CNCs) i agents antimicrobians (oli de neem-N, oli essencial d'orenga-O i nanopartícules de plata). També es va fer un estudi de biodegradació de les pel·lícules per observar l'efecte dels antimicrobians. Entre els diferents midons amb distint ràtio amilosa:amilopectina, es va seleccionar el midó de pèsol amb alts valors d'amilosa. L'alt contingut en amilosa va donar lloc a pel·lícules més rígides i resistents a la fractura, amb baixa permeabilitat a l'oxigen, la qual va disminuir durant l'emmagatzemament. Les pel·lícules de mescla de S-PVA van representar una bona estratègia per a millorar les propietats de les pel·lícules sense incrementar notablement el preu. L'addició de PVA va donar lloc a pel·lícules menys solubles en aigua, menys sensibles a la seua absorció i més extensible i resistents que les de midó pur. A més van mantenir l'alta barrera a l'oxigen i van donar estabilitat a la matriu durant l'envelliment. Son recomanables les ràtios de S- PVA pròxims a 1:1. El segó d'arròs amb menor tamany de partícula, va millorar el mòdul elàstic de les pel·lícules, però la seua extensibilitat i propietats barrera van empitjorar. La incorporació de CNCs en les pel·lícules de S-PVA, va incrementar la separació de fases dels polímers, sense implicar canvis en la permeabilitat al vapor d'aigua, però millorant les prestacions mecàniques: pel·lícules més rígides i extensibles, al mateix temps que es va inhibir parcialment la cristal·lització del PVA. Les pel·lícules de S-PVA amb partícules de plata van exhibir activitat antimicrobiana front a dos de fongs i dos bacteris, depenent de la concentració de plata. Les AgNPs van provocar canvis en el color de les pel·lícules així com en la seua transparència. La plata va ser completament alliberada en els primers 60 minuts en contacte amb simulants aquosos. La capacitat d'alliberament va disminuir en simulants no polars, on es complix el límit de migració global. Per tant, l'ús de les pel·lícules desenvolupades per a l'envasat d'aliments ha de ser restringit a productes alimentaris rics en greixos. La incorporació d'O en la matriu de S-PVA va donar lloc a pel·lícules actives front a bacteris i fongs. Pel contrari les pel·lícules amb N no van ser efectives. Van ser necessàries concentracions més elevades d'O en les pel·lícules per a observar un efecte antifúngic respecte a l'activitat bactericida. Els olis no van afectar la sensibilitat a l'aigua ni les propietats barrera a l'aigua de les pel·lícules, però la major proporció d'oli va donar lloc a pel·lícules amb una xarxa més dèbil, afectant les seues prestacions mecàniques. La mescla de S amb PVA va millorar significativament el comportament de biodegradació i desintegració. La incorporació de partícules de plata a pel·lícules de S-PVA va disminuir la seua cinètica de biodegradació mentre que va augmentar la seua ràtio de degradació. No obstant això, l'addició d'O no va presentar un efecte significatiu en els índexs de biodegradació a pesar de l'activitat antimicrobiana detectada. L'N fins i tot va millorar la biodegradació de les pel·lícules de S-PVA. Finalment, es va realitzar una aplicació de recobriments basats en biopolímers, fent ús de quistosà-CH i olis essencials de orenga i romer per evitar la pèrdua de pes i el desenvolupament de fongs en formatges de cabra semi-curats. Els recobriments van ser altament efectius en la reducció del creixement fúngic i la pèrdua de pes dels formatges. L'activitat lipolítica i proteolítica en els formatges va disminuir suaument. L'anàlisi sensorial va revelar que els form / Cano Embuena, AI. (2015). Different strategies to improve the functionality of biodegradable films based on starch and other polymers [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/55383 / Premios Extraordinarios de tesis doctorales / Compendio