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1	Membranas condutoras iônicas de celulose bacteriana / Salvi, Denise Toledo Bonemer De. January 2010 (has links) Orientador: Younés Messaddeq / Coorientador: Agnieszka Joanna Pawlicka Maule / Banca: Caio Eduardo de Campos Tambelli / Banca: Rogéria Rocha Gonçalves / Resumo: Esta dissertação apresenta a preparação e caracterização de membranas condutoras iônicas baseadas em celulose produzida pela bactéria Gluconacetobacter xylinus. Estas membranas foram preparadas a partir da imersão de membranas de celulose bacteriana (CB) em soluções aquosas de ácidos (ácido acético e ácido trifluoroacético) e/ou plastificantes (trietanolamina e glicerol). Estrutura e perfil térmico destas membranas condutoras foram investigados por difração de raios X (DRX), microscopia eletrônica de varredura (MEV), termogravimetria (TG), calorimetria exploratória diferencial (DSC), espectroscopia vibracional na região do infravermelho (FTIR) e espectroscopia de espalhamento Raman. As propriedades elétricas foram avaliadas utilizando-se espectroscopia de impedância eletroquímica (EIE). As análises de DRX mostram o aumento de plastificante diminui a cristalinidade das amostras, cujo recobrimento das microfibrilas pelo plastificante pode ser visualizado por análise de MEV, e os valores de condutividade iônica obtidos são maiores em comparação aos da CB seca. A condutividade na membrana é dependente do conteúdo de umidade e o plastificante age impedindo a desidratação da membrana. Foi observado também que combinações de ácido e plastificante resultaram em membranas com maiores condutividades do que aquelas em que houve apenas adição do plastificante, uma vez que a adição de ácidos pode aumentar a condutividade protônica / Abstract: This dissertation presents the preparation and characterization of ionic conducting membranes based on cellulose produced by bacteria Gluconacetobacter xylinus. These membranes have been prepared from bacterial cellulose membranes (BC) soaked in acids (acetic and trifluoroacetic acids) and/or plasticizer (triethanolamine and glycerol) aqueous solutions. The structure and thermal behavior of the conducting membranes were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry (TG), differential scanning calorymetry (DSC), infrared spectroscopy (FTIR) and Raman spectroscopy. Electrical properties were performed utilizing electrochemical impedance spectroscopy (EIS). From XRD analyses the amorphous phase becomes larger after increasing the amount of plasticizer that covers the cellulose microfibrils as revealed by SEM, and the obtained conductivity values were high in comparison to dried BC. The conductivity in the membrane is dependent on the moisture content and the plasticizer acts avoiding complete membrane dryness. It was also observed that the combination of acid and plasticizer resulted in membranes with higher ionic conductivity than plasticized ones, once the addition of acids may improve protonic conductivity / Mestre Celulose. Membranas. Bacterial cellulose. eng Ionic conducting membranes. eng
2	Membranas condutoras iônicas de celulose bacteriana Salvi, Denise Toledo Bonemer De [UNESP] 17 December 2010 (has links) (PDF) Made available in DSpace on 2014-06-11T19:29:09Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-12-17Bitstream added on 2014-06-13T19:58:43Z : No. of bitstreams: 1 salvi_dtb_me_araiq.pdf: 8254301 bytes, checksum: 206fba452475ee19cd840bec61eb7015 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Esta dissertação apresenta a preparação e caracterização de membranas condutoras iônicas baseadas em celulose produzida pela bactéria Gluconacetobacter xylinus. Estas membranas foram preparadas a partir da imersão de membranas de celulose bacteriana (CB) em soluções aquosas de ácidos (ácido acético e ácido trifluoroacético) e/ou plastificantes (trietanolamina e glicerol). Estrutura e perfil térmico destas membranas condutoras foram investigados por difração de raios X (DRX), microscopia eletrônica de varredura (MEV), termogravimetria (TG), calorimetria exploratória diferencial (DSC), espectroscopia vibracional na região do infravermelho (FTIR) e espectroscopia de espalhamento Raman. As propriedades elétricas foram avaliadas utilizando-se espectroscopia de impedância eletroquímica (EIE). As análises de DRX mostram o aumento de plastificante diminui a cristalinidade das amostras, cujo recobrimento das microfibrilas pelo plastificante pode ser visualizado por análise de MEV, e os valores de condutividade iônica obtidos são maiores em comparação aos da CB seca. A condutividade na membrana é dependente do conteúdo de umidade e o plastificante age impedindo a desidratação da membrana. Foi observado também que combinações de ácido e plastificante resultaram em membranas com maiores condutividades do que aquelas em que houve apenas adição do plastificante, uma vez que a adição de ácidos pode aumentar a condutividade protônica / This dissertation presents the preparation and characterization of ionic conducting membranes based on cellulose produced by bacteria Gluconacetobacter xylinus. These membranes have been prepared from bacterial cellulose membranes (BC) soaked in acids (acetic and trifluoroacetic acids) and/or plasticizer (triethanolamine and glycerol) aqueous solutions. The structure and thermal behavior of the conducting membranes were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry (TG), differential scanning calorymetry (DSC), infrared spectroscopy (FTIR) and Raman spectroscopy. Electrical properties were performed utilizing electrochemical impedance spectroscopy (EIS). From XRD analyses the amorphous phase becomes larger after increasing the amount of plasticizer that covers the cellulose microfibrils as revealed by SEM, and the obtained conductivity values were high in comparison to dried BC. The conductivity in the membrane is dependent on the moisture content and the plasticizer acts avoiding complete membrane dryness. It was also observed that the combination of acid and plasticizer resulted in membranes with higher ionic conductivity than plasticized ones, once the addition of acids may improve protonic conductivity Celulose Membranas Celulose bacteriana Membranas condutoras iônicas Bacterial cellulose Ionic conducting membranes
3	High Performance Materials Containing Nitrile Groups Sumner, Michael Jameson 24 April 2003 (has links) The objective of the research described in this thesis has been to improve the toughness of phenolic networks while maintaining flame resistance. A four step synthetic scheme has been developed to prepare 4,4′-Bis(3,4-dicyanophenoxy)biphenyl(biphenoxyphthalonitrile). A 700 g mol-1 novolac oligomer was cured with relatively low concentrations of this reagent (~20 wt %) into high Tg (~190 °C) networks. The curing reaction was attrubuted to nucleophilic attack of the phenolic hydroxyl on the nitrile groups of the phthalonitrile resulting in the formation of heterocylic rings. TGA and cone calorimetry demonstrated that these networks have excellent thermo-oxidative stability. Further goals were to develop halogen-free, flame retardant monomers for improving the thermo-oxidative resistance of polystyrene and dimethylacrlyate/styrene(vinyl ester) networks. 4-Vinylphenoxyphthalonitrile, a phthalonitrile derivative of styrene, was synthesized. FTIR has been utilized to demonstrate this new monomer co-cured into vinyl ester networks in free radical thermosetting polymerizations. Upon post-curing the networks between 200-260 °C for ~1.5 h, the nitrile groups reacted to form heterocyclic crosslinks. TGA and cone calorimetry demonstrated that the 4-vinylphenoxyphthalonitrile substantially improved the flame resistance of vinyl ester networks. Copolymerizations of styrene and 4-vinylphenoxyphthalonitrile were conducted at 75 °C for 24 h using 0.5 wt % AIBN in chlorobenzene. Dynamic TGA at 10 °C min-1 in air showed that copolymers containing 10 and 25 mole % of 4-vinylphenoxyphthalonitrile had increased initial weight loss temperatures in air by (~50 °C higher) and increased the char yield between 400-600 °C. High molecular weight nitrile-functional, (hexafluoroisopropylidene)diphenol based aromatic poly(arylene ether)s with pendent sulfonic acid groups were prepared by nucleophilic step copolymerization of 4,4′-(hexafluoroisopropylidene)diphenol, 2,6-dichlorobenzonitrile, and 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone under basic conditions in N-methyl-2-pyrrolidinone at 200 °C. A series of these materials with systematically varied concentrations of the sulfonic acid moieties showed increased glass transition temperatures, proton conductivities, and hydrophilicities as a function of disulfonation. Atomic force microscopy (AFM) demonstrated that the acidified copolymer with 35 mole % of disulfonated units was phase separated into a co-continuous morphology of hydrophobic and hydrophilic domains. / Ph. D. vinyl ester networks phthalonitrile polystyrene copolymers phenolic networks proton conducting membranes
4	Blending of Proton Conducting Copolymers Weißbach, Thomas 20 October 2010 (has links) (PDF) Highly proton conducting polymers for operation in hydrogen/oxygen proton exchange membrane fuel cells (PEMFCs) provide often a poor mechanical strength due to high water contents. To strengthen the conducting polymers, blends with different ratios of partially fluorinated sulfonic acid graft and diblock copolymers with perfluorinated polymers were prepared. To analyze the effect of the different quantities of the compounds, with regard to water sorption and proton conducting properties, membranes were prepared by dissolving the components and drop casting. Partially sulfonated poly([vinylidene difluoride-co-chlorotrifluoroethylene]-g-styrene) (P(VDF-co-CTFE)-g-SPS) was blended with polyvinylidene difluoride (PVDF), decreasing the ion exchange capacity (IEC). The blended polymers absorbed less water. However, the by AC impedance spectroscopy determined proton conductivity stayed stable or increased slightly. The effective proton mobility remained constant. Partially sulfonated poly([vinylidene difluoride-co-hexafluoropropylene]-b-styrene) (P(VDF-co-HFP)-b-SPS) with two different PS-block lengths were blended with different amounts of poly(vinylidene difluoride-co-hexafluoropropylene) (P(VDF-co-HFP)). In that case, the polymers absorbed less water and the proton conductivity decreased stepwise by adding more than 20 wt% P(VDF-co-HFP). The results indicate that a blending of P(VDF-co-CTFE)-g-SPS with PVDF inhibits swelling without having an effect on the proton conductivity, though water sorption and IEC are reduced. Brennstoffzelle Pfropfcopolymere Copolymere Diblockcopolymere Mischen Elektrolytische Leitfähigkeit Wasseraufnahme Polyelektrolyt Atom-Transfer-Polymerisation Emulsionspolymerisation Protonenmobilität PEMFC PEM Ionomer Ionenaustauschkapazität IEC PEMFC PEM Fuel Cell Proton Exchange Membrane Proton Conductivity Blending Ionomers Copolymers Proton Mobility IEC Ion Exchange Capacity Conducting Membranes Block-Copolymer Graft-Copolymer Proton-Exchange Membranes Ionomer ddc:540 Brennstoffzelle Pfropfcopolymere Copolymere Diblockcopolymere Mischen Elektrolytische Leitfähigkeit Wasseraufnahme Polyelektrolyt Atom-Transfer-Polymerisation
5	Blending of Proton Conducting Copolymers Weißbach, Thomas 08 October 2010 (has links) Highly proton conducting polymers for operation in hydrogen/oxygen proton exchange membrane fuel cells (PEMFCs) provide often a poor mechanical strength due to high water contents. To strengthen the conducting polymers, blends with different ratios of partially fluorinated sulfonic acid graft and diblock copolymers with perfluorinated polymers were prepared. To analyze the effect of the different quantities of the compounds, with regard to water sorption and proton conducting properties, membranes were prepared by dissolving the components and drop casting. Partially sulfonated poly([vinylidene difluoride-co-chlorotrifluoroethylene]-g-styrene) (P(VDF-co-CTFE)-g-SPS) was blended with polyvinylidene difluoride (PVDF), decreasing the ion exchange capacity (IEC). The blended polymers absorbed less water. However, the by AC impedance spectroscopy determined proton conductivity stayed stable or increased slightly. The effective proton mobility remained constant. Partially sulfonated poly([vinylidene difluoride-co-hexafluoropropylene]-b-styrene) (P(VDF-co-HFP)-b-SPS) with two different PS-block lengths were blended with different amounts of poly(vinylidene difluoride-co-hexafluoropropylene) (P(VDF-co-HFP)). In that case, the polymers absorbed less water and the proton conductivity decreased stepwise by adding more than 20 wt% P(VDF-co-HFP). The results indicate that a blending of P(VDF-co-CTFE)-g-SPS with PVDF inhibits swelling without having an effect on the proton conductivity, though water sorption and IEC are reduced.:1 Introduction 2 Literature Review 2.1 Fuel Cells 2.1.1 Proton Exchange Membrane Fuel Cells 2.1.2 Other Types of Fuel Cells 2.2 Proton Conductivity 2.3 Proton Conducting Polymers 2.4 Impedance Spectroscopy 2.5 Polymers 2.6 Blending 2.7 Synthesis 2.7.1 Atom Transfer Radical Polymerization 2.7.2 Emulsion Polymerization 3 Results 3.1 Synthesis 3.1.1 Polyvinylidene Diuoride (PVDF) 3.1.2 Diblock Copolymers P(VDF-co-HFP)-b-SPS and Blends 3.1.3 Graft Copolymer P(VDF-co-HFP)-b-SPS Blends 3.2 Degree of Sulfonation 3.3 Ionomer Content 3.4 Ion Exchange Capacity 3.5 Water Content and Uptake 3.6 Proton Concentration 3.7 Watermolecules per Ionic Group 3.8 Proton Conductivity 3.9 Proton Mobility 4 Discussion & Conclusion 5 Experimental Part 5.1 Synthesis 5.1.1 Synthesis of PVDF 5.1.2 Synthesis of P(VDF-co-HFP)-b-PS 5.1.3 Sulfonation of the Polystyrene Block 5.2 Polymer Characterization 5.3 Membrane Preparation 5.4 Membrane Characterization Bibliography Appendix info:eu-repo/classification/ddc/540 ddc:540

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