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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
181

Solid state optical conjugated polymer amplifier, with ultrafast gain switching

Amarasinghe, Dimali C. V. January 2008 (has links)
Conjugated polymers are organic materials which are attractive as optoelectronic devices because they have a combination of broad band emission, high gain, versatility in processing, are ductile and can be electrically pumped. This thesis describes work conducted on such conjugated polymers as amplifier devices. The conjugated polymers used in this thesis were MEH-PPV, F8BT, GP1302 and ADS233YE. The amplifier devices used were grating coupled and end coupling waveguides. Amplification of light was demonstrated and characterised on single and multiple pulses using the grating coupled structure. Single pulse measurements obtained gains of 21 and 17 dB in a 1 mm long waveguide using the conjugated polymers MEHPPV and F8BT. Annihilation rate was also analysed in the single pulse method with MEH-PPV, giving a value of γ ≈ (3 ± 0.1) x 10⁻⁹ cm³/s. Amplification of a single pulse led to demonstrate amplification and the capability of the amplifier to function with multiple pulses, which resulted in F8BT being used as the gain medium. An average gain of 18 dB was obtained with F8BT in a 1 mm waveguide channel. Amplification was also investigated with end coupled waveguides. This led into investigating a suitable material or suitable combination of material for amplification with the waveguides. Switching of an amplified pulse was attempted on F8BT and GP1302 in the amplifier device at 5 kHz. Switching of F8BT was problematic which lead to attempt switching in GP1302 which was a co-polymer of PFO and F8BT. A 70 % switching effect was obtained with GP1302. Gain recovery dynamics of F8BT, GP1302 and ADS233YE was also investigated. These measurements established a switching rate of 500 GHz for GP1302 and ADS233YE, and F8BT showed partial gain recovery indicating the presence of long lived species. Switching was also attempted on a polymer laser. This resulted in a 100 % switched pulse with a combination of weak pump and strong switch pulse of 40 nJ and 2 μJ respectively. And a strong pump and weak switch pulse of 200 and 50 nJ respectively. Temporal delay of the switch pulse relative to the pump pulse resulted in re-timing of the laser output. Amplification and switching of light pulses were also attempted at a higher repetition rate of 50 kHz with F8BT, GP1302, ADS233YE and MEH-PPV. This resulted in strong amplification of light in MEH-PPV and F8BT with gains of 21 and 13 dB respectively in a waveguide length of 422 μm. Weak amplification of light in ADS233YE and GP1302 was also obtained with a maximum gain of 8 and 3 dB respectively. Switching was attempted on MEH-PPV and ADS233YE.
182

Conducting metallopolymers with tridentate ligands and coordination chemistry with corresponding model compounds

Keskin, Şeyma 22 July 2014 (has links)
Conducting polymers that contain metals are remarkable materials, because they have the properties of both organic backbones and metals. Depending on the position of the metal relative to the conjugated backbone, i.e. attached to or directly in the backbone, these two can couple resulting in advancement of the functionality and therefore potential applications of these types of materials. Complexes of tridentate ligands with donor atoms such as phosphorus, nitrogen, and sulfur also have a wide variety of applications. In addition, complexes of tridentate ligands have advantages of stability and control of electron density by variation of donor atoms. Therefore, conjugated polymers with tridentate ligand units will have promise for various applications and advantages in their designs. Complexes of PNP ligand with molybdenum and carbonyl ancillary ligands were synthesized and characterized. Isomerization and conversion reactions between them were investigated as well as the coordination modes. Many types of PNP ligands have been studied in the literature because the hemilabile property of the nitrogen atom promotes some catalytic reactions and gives different coordination geometries. Conducting polymers can be used as redox-active ligands and they can be used to control electron density on the metal attached to them. Synthesis and characterization of a novel polymerizable ligand 3,5-bis-EDOT-N,N-bis[2-diphenylphosphinoethyl]aniline was achieved. Related molybdenum complexes with ancillary ligands as carbonyls were also synthesized and characterized. Monomer complexes and the free ligand were electropolymerized and studied. Tris(bipyridine)ruthenium(II) chloride and analogous complexes have been studied extensively in the literature due to their luminescent and photochemical properties, and excited state lifetimes. Conducting polymers with similar ruthenium groups have been investigated for various applications. Synthesis of four ruthenium complexes with the polymerizable ligand 2,6-Bis[4-[2-(3,4-diethylenedioxy)thiophene]pyrazol-1-yl]pyridine and four different bidentate ligands were reproduced; electropolymerizations of the complexes were achieved; electrochemical, UV-Vis and luminescence studies were performed and discussed. Various complexes of copper, silver, platinum, and palladium with nitrogen and phosphorus donors have been reported for their luminescence behavior as well as their interesting structures. Model complexes of these metals with N,N-bis[2-(diphenylphosphino)ethyl]phenyl-amine (a PNP ligand) have been synthesized and characterized. Absorption and luminescence behaviors as well as the coordination modes were investigated. / text
183

Ultraspartus optinis krūvininkų dreifo zondavimas konjuguotųjų polimerų plėvelėse / Charge carrier transport in conjugated polymer films revealed by ultrafast optical probing

Devižis, Andrius 22 February 2011 (has links)
Konjuguotieji polimerai kaip funkcinės medžiagos gali būti panaudoti įvairiuose prietaisuose: organiniuose šviestukuose, organiniuose lauko tranzistoriuose, organiniuose saulės elementuose. Šio darbo tikslas - nustatyti fotogeneruotų krūvininkų pernašos dėsningumus π – konjuguotuose polimeruose panaudojant naują žadinimo-zondavimo metodą pagrįstą išoriniu elektriniu lauku indukuota antrosios optinės harmonikos generacija. Pagrindinis dėmesys buvo skiriamas pernašos dinamikai. Molekulinių darinių fizikos laboratorijoje buvo įrengta matavimų schema ir įvertintas metodo tinkamumas krūvio pernašos tyrimams. Buvo atlikti krūvio pernašos matavimai trijuose skirtinguose konjuguotuosiuose polimeruose. Nustatyta, kad fotogeneruotų krūvininkų judris tuoj po sužadinimo yra daug didesnis lyginant su stacionaria judrio verte, o krūvio pernašos dinamiką lemia konjuguoto polimero struktūrinė hierarchija, krūvininkų judėjimas yra daugialypis, susidedantis iš greito judėjimo viena polimero grandine ar konjuguotais polimero grandinės segmentais ir lėto šokavimo tarp atskirų polimero grandinių Pirmą kartą detaliai išnagrinėta šviesa sugeneruotų krūvininkų pernašos dinamika konjuguotuose polimeruose. Darbo rezultatai suteikia žinių apie fundamentalius krūvininkų pernašos mechanizmus konjuguotuose polimeruose, kurios gali būti panaudotos kuriant organinius elektronikos prietaisus. / Conjugated polymers are promising candidates for applications in all kinds of organic optoelectronic devices: OLEDs, organic field-effect transistors (OFETs) and organic photovoltaic cells. The main goal of this work was to investigate transport features of photogenerated electrical charge in pi-conjugated polymers by means of novel technique based on time-resolved electric field-induced second harmonic generation (TREFISH). TREFISH measurement setup was implemented in the laboratory of Molecular compounds physics, and applicability of the method has been verified. Measurements were performed on three different model polymers: methyl substituted ladder-type poly(para-phenylene) (MeLPPP), poly(fluorene-co-benzothiadiazole) (F8BT) and poly(spirobifluorene-co-benzothiadiazole) (PSF-BT), having different morphological and chemical structure. It has been found that motion of photogenerated charge carriers in π-conjugated polymer films experiences rapid dynamics after excitation. Different time domains of charge transport were distinguished. Initial fast transport of photogenerated charge carriers corresponds to the carrier motion along the single polymer chain or conjugated segment of the polymer chain. Slowest carrier motion phase is well described by the stochastic drift, which is attributed to interchain jumps and determines the macroscopic equilibrium mobility. Thus, the equilibrium mobility value is not applicable to the transport on nanometer scale up to tens of nanometers... [to full text]
184

Ultrafast organic lasers and solid-state amplifiers

Goossens, Mark January 2007 (has links)
This thesis presents an investigation of the lasing dynamics and optical amplification devices using conjugated polymers. Spectroscopic studies of conjugated polymers and dendrimers were also performed. Conjugated polymers and dendrimers are materials with great potential as display materials and tuneable lasers due to their broad spectra and high optical gains. The effect of conjugation is studied in MEH-PPV and an anisotropy measurement of two different cored dendrimers has been shown to verify a theoretical prediction on their depolarisation. Singlet emission from a highly efficient phosphorescent dendrimer is also observed and is the first known report of fluorescence from this class of dendrimers. Conjugated polymers exhibit optical gain over broad spectral ranges, which has led to much interest in their potential as novel laser gain media. Investigations into lasing from conjugated polymers has been confined mainly to studying the lasing properties and not the temporal dynamics of the laser pulses. In this work an investigation into the lasing dynamics of a 2D-DFB conjugated polymer laser is demonstrated with the first subpicosecond laser pulses observed for a polymer laser. A novel encapsulated laser fabricated via a soft lithography route was also studied and exhibited laser pulse of 6 ps duration. The high gain observed over broad spectral ranges also means that these materials are suitable for use as optical amplifiers. Broadband gain in a conjugated polymer solution was demonstrated with a gain of 30 dB accessible across a 60 nm wavelength range. In the solid state the limited thickness of films (~ 100 nm) and the uneven nature of the film edges had limited the ability to study the amplification of a probe signal. The first practical solid state conjugated polymer amplifier has been demonstrated. The device uses grating structures to couple a probe signal into and out of the gain region. The gain dynamics of different length amplifiers were studied and an 18 dB gain was observed in a 300 µm device length using a conjugated polymer blend of RedF and F8BT. Further work on a conjugated polymer MEH-PPV led to a 21dB gain in a 1 mm device.
185

Monopolar and Bipolar Membranes in Organic Bioelectronic Devices

Gabrielsson, Erik O. January 2014 (has links)
In the 1970s it was discovered that organic polymers, a class of materials otherwise best know as insulating plastics, could be made electronically conductive. As an alternative to silicon semiconductors, organic polymers offer many novel features, characteristics, and opportunities, such as producing electronics at low costs using printing techniques, using organic chemistry to tune optical and electronic properties, and mechanical flexibility. The conducting organic polymers have been used in a vast array of devices, exemplified by organic transistors, light-emitting diodes, and solar cells. Due to their softness, biocompatibility, and combined electronic and ionic transport, organic electronic materials are also well suited as the active material in bioelectronic applications, a scientific and engineering area in which electronics interface with biology. The coupling of ions and electrons is especially interesting, as ions serve as signal carriers in all living organisms, thus offering a direct translation of electronic and ionic signals. To further enable complex control of ionic fluxes, organic electronic materials can be integrated with various ionic components, such as ion-conducting diodes and transistors. This thesis reports a background to the field of organic bioelectronic and ionic devices, and also presents the integration of ionic functions into organic bioelectronic devices. First, an electrophoretic drug delivery device is presented, capable of delivering ions at high spatiotemporal resolution. The device, called the organic electronic ion pump, is used to electronically control amyloid-like aggregation kinetics and morphology of peptides, and offers an interesting method for studying amyloids in vitro. Second, various ion-conducting diodes based on bipolar membranes are described. These diodes show high rectification ratio, i.e. conduct ions better for positive than for negative applied voltage. Simple ion diode based circuits, such as an AND gate and a full-wave rectifier, are also reported. The AND gate is intended as an addressable pH pixel to regulate for example amyloid aggregation, while the full-wave rectifier decouples the electrochemical capacity of an electrode from the amount of ionic charge it can generate. Third, an ion transistor, also based on bipolar membranes, is presented. This transistor can amplify and control ionic currents, and is suitable for building complex ionic logic circuits. Together, these results provide a basic toolbox of ionic components that is suitable for building more complex and/or implantable organic bioelectronic devices.
186

Electrochromism and over-oxidation in conjugated polymers: Improved color switching and a novel patterning approach

Tehrani, Payman January 2006 (has links)
During the last 30 years a new research and technology field of organic electronic materials has grown thanks to a groundbreaking discovery made during the late 70’s. This new field is today a worldwide research effort focusing on exploring this new class of materials that also enable many new areas of electronics applications. In the organic electronics research field conducting organic molecules and polymers are synthesized and used in devices. The reason behind the success of conducting polymers is the flexibility to develop materials with new functionalities via clever chemical design and the possibility to use low-cost production techniques to manufacture devices. This thesis reviews and describes different aspects of the organic electronics, here focusing on electrochromic displays; device improvements, the study of degradation and also patterning technology for rational manufacturing processing. The color contrast in electrochromic displays based on conjugated polymers was increased with approximately a factor of two by adding an extra electrochromic polymer. It was found that electrochemical over-oxidation (ECO) limits the flexibility in choosing desired electrochromic materials. ECO is one of the main degradation mechanisms in electrochromic displays. ECO is an efficient and fast process to permanently reduce the electronic conductivity in polythiophenes. From this, a novel patterning process was developed, in which the films of polythiophenes can be patterned through local and controlled deactivation of the conductivity. The ECO has been combined with different patterning tools to enable the use of existing printing tools for manufacturing. In combination with screen-printing, low-cost and high volume roll-to-roll patterning was demonstrated, while together with photolithography, patterning down to 2 µm can be achieved. Systematic studies have shown that conductivity contrasts beyond 107 can be achieved, which is enough for various simple electronic systems. To generate better understanding of the ECO phenomena the effect of pH on the over-oxidation characteristics was studied. The results suggest that a part of the mechanism for over-oxidation depends on the OH– concentration of the electrolyte used.
187

Fotogenerace nosičů náboje v substituovaných polyacetylenech / Photogeneration of charge carriers in substituted polyacetylenes

Jex, Michal January 2013 (has links)
We present an improved model of charge carrier photogeneration in π-conju- gated polymers with weak intermolecular interactions based on the model of Arkhipov. It includes quantum effects affecting the creation of charge transfer states, which occurs as an intermediate step in the free charge carrier photo- generation process. The electrostatic potential between the electron and the hole and transfer integrals needed for the calculation of the potential barrier for the charge transfer state dissociation are calculated quantum-chemically. We apply our model on experimental data of the charge carrier photogenera- tion efficiency in poly[1-trimethylsilylphenyl,2-phenyl]acetylene to explain its dependence on applied electric field. We eliminate several problems of the previous model. We are able to fit experimental data with just one set of parameters in the whole interval of the applied electric field. We do not have to consider several intervals of the electric field separately as in the previous work and reduce the number of needed parameters to three. Key words π-conjugated polymers, charge carrier photogeneration, photoconductivity 1
188

Qualidade da carne maturada de bovinos Nelore terminados em confinamento /

Pivaro, Thiago Martins. January 2011 (has links)
Resumo: No presente trabalho, avaliou-se o efeito do processo de maturação na qualidade da carne do músculo Longissimus de 35 tourinhos da raça Nelore confinados por 96 dias e abatidos com peso de 532,17 ± 30,25kg e 24 meses de idade. Os animais foram alimentados com uma dieta controle sem a adição de óleo e outras quatro dietas contendo diferentes fontes de óleo (soja ou linhaça) protegido ou não da degradação ruminal. Após o abate e 24 horas de resfriamento foram retirados 3 bifes de 2,5cm de espessura entre a 12a e 13a costelas do músculo Longissimus, posteriormente embalados à vácuo e maturados em estufa B.O.D. à temperatura de 2oC durante 7, 14 e 21 dias. Em seguida, foram analisadas as seguintes características: força de cisalhamento, ph, cor, perdas na maturação e composição química da carne assada. Após liofilização, o extrato etéreo foi extraído, metilado e as leituras realizadas por cromatografia gasosa. O delineamento estatístico utilizado foi em blocos casualizados, sendo 5 tratamentos, em 7 blocos e utilizadas 4 medidas repetidas no tempo. As variáveis foram avaliadas por meio de análise de variância e teste t Student à 5% de probabilidade e para as características sensoriais da carne foi utilizado o teste não paramétrico de Kruskal-Wallis. Houve efeito significativo para as variáveis matéria seca, extrato etéreo e matéria mineral. A força de cisalhamento apresentou diferenças entre os grupos de bifes maturados, (5,97; 4,31; 3,25 e 2,96kgf/cm2, para 0, 7, 14 e 21 dias de maturação, respectivamente), sendo que o tempo 14 e 21 foram mais macios que o tempo 7, e este, mais macio que o tempo 0. O ph apresentou diferença entre a carne in natura e os períodos de maturação. Houve efeito significativo para a maturação das variáveis luminosidade, intensidade da cor vermelha e intensidade da cor amarela. As perdas por exsudação na maturação ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In this study, we assess the effect of the ageing process in the meat quality of Longissimus muscles from 35 Nellore bulls young bulls confined for 96 days and slaughtered weighing 532.17 ± 30.25 kg and 24 months of age. The animals were fed with five different diets: the first one was a control diet, without oil and the other four diets containing different oil sources (soy or flaxseed) protected or not from ruminal degradation. After slaughter and 24 hours of cooling, 3 samples with 2.5 cm thickness were removed between the 12th and 13th ribs of Longissimus muscles and subsequently vacuum packaged and aged in an environmental chamber at a temperature of 2o C for 7, 14 and 21 days. We assess the characteristics: shear force, pH, color, ageing losses, chemical composition and fatty acids of meat. The fatty acids were assess by gas chromatography. Variables were evaluated by analysis of variance and Student t test at 5% probability and the sensory characteristics of meat was used nonparametric Kruskal-Wallis test. Shear force differed between the ageing groups, (5.97; 4.31, 3.25 and 2.96 Kgf/cm2 to 0, 7, 14 and 21 days) the period 14 and 21 were softer than the period 7. The pH was different between the fresh beef and the other periods. There was a significant effect on the variable lightness, red color intensity and intensity of yellow color. The losses were larger as the period of ageing increased, and the period of 21 days showed 5.58% of losses. The sensory evaluation showed the difference to variable smoothness for the period of 7 days.. There was a significant effect on concentration of myristic acids (C14: 0), miristoleico \ (C14: 1), pentadecanoic (C15: 0), palmitic (C16: 0), palmitoleic (C16: 1) vacênico (C18: 1 n7) and oleic (C18: 1 n9). In contrast there was an increase in the levels of stearic (C18: 0), linoleic (C18: 2 n6) eicosenoic (C20: 1 n9), eicosadienoico (C20: 2) ... (Complete abstract click electronic access below) / Orientador: Alexandre Amstalden Moraes Sampaio / Coorientador: Wignez Henrique / Banca: Hirasilva Borba / Banca: Alexandre Rodrigo Mendes Fernandes / Mestre
189

Desenvolvimento de iogurte probiótico com adição de polpa de frutos brasileiros e fibra dietética total / Development of probiotic yoghurt with addition of Brazilian´s fruit pulp and total dietary fiber

Santo, Ana Paula do Espirito 09 February 2012 (has links)
Novas tendências para desenvolvimento de leites fermentados com elevado valor agregados são o uso de frutos da Amazônia e a utilização de subprodutos de certas frutas como forma de aproveitamento integral do fruto e para minimizar a produção de resíduos. Dentre os frutos da Amazônia o açaí (Euterpe oleracea Mart., Arecaceae) tem o maior potencial enquanto alguns subprodutos de frutos como as cascas de maçã, banana e maracujá são promissores como ingredientes especialmente devido ao seu conteúdo em fibras dietéticas solúveis prebióticas como pectina e frutooligossacarídeos, que conferem propriedades funcionais além das características nutricionais das frutas. Assim, esse trabalho visou o desenvolvimento de iogurte probiótico com adição de polpa de frutos brasileiros e fibra dietética total. Os efeitos da suplementação do leite com polpa de açaí e fibras de maçã, banana e maracujá e, diferentes bactérias probióticas - Lactobacillus acidophilus L10, Bifidobacterium animalis ssp. lactis Bl04 e B94 e Bifidobacterium longum Bl05 na cinética de acidificação, viabilidade dos probióticos, perfil de ácidos graxos, textura, reologia e microestrutura foram estudados. A polpa de açaí favoreceu uma maior contagem de L. acidophilus L10, B. animalis ssp. lactis Bl04 e B. longum Bl05 em relação aos respectivos controles ao final de quatro semanas de vida de prateleira. Além disso, em relação aos controles sem polpa, a polpa de açaí aumentou o conteúdo de ácidos graxos mono e poliinsaturados e a produção de ácido α-linolênico (ALA) e ácido linoléico conjugado (CLA) em iogurtes desnatados co-fermentados com B. animalis ssp. lactis cepas Bl04 e B94. Todas as fibras foram capazes de aumentar a concentração de ácidos graxos de cadeia curta e poliinsaturados nos iogurtes, mas, apenas as fibras de maçã e banana aumentaram a viabilidade das bactérias probióticas durante a vida de prateleira em relação aos controles sem fibra. Foi observado um efeito sinérgico entre o tipo de fibra e a cepa probiótica sobre o teor de CLA. Por outro lado, a quantidade de ALA foi significativamente aumentada pela adição de fibra de banana, independentemente da cepa probiótica utilizada. A fibra de maracujá promoveu o aumento CLA em todos os iogurtes probióticos. Os resultados demonstram, pela primeira vez, que tanto a polpa de açaí quanto as fibras oriundas do subproduto do processamento de maçã, banana ou maracujá podem melhorar o perfil de ácidos graxos e a viabilidade de bactérias probióticas. Além disso, a fibra de casca de maracujá teve um efeito positivo sobre a textura de iogurtes desnatados co-fermentados por bifidobacteria. / New trends for development of fermented milk products with high added value are the use of fruits from Amazon, and the use of by-products of certain fruits as ingredients as a way to take full advantage of the fruit and to minimize the waste. Among the fruits of the Amazon, açai (Euterpe oleracea Mart., Arecaceae) has the most potential, and byproducts of some fruits such as apple peels, banana and passion fruit as ingredients are especially promising because of its content in dietary fiber such as pectin and soluble prebiotic fructooligosaccharides, which confer functional properties in addition to the nutritional characteristics of fruits. Thus, this study aimed the development of probiotic yoghurt with added fruit pulp from Brazil and total dietary fiber. The effects of supplementation of milk with acai pulp fiber and apple, banana and passion fruit, and different probiotic bacteria - Lactobacillus acidophilus L10, Bifidobacterium animalis ssp. Bl04 lactis and Bifidobacterium longum B94 and Bl05 on the kinetics of acidification and viability of probiotics, fatty acid profile, texture, rheology and microstructure were studied. The açaí favored a higher count of L. acidophilus L10, B. animalis ssp. and B. lactis Bl04 Bl05 longum compared with their controls after four weeks of shelf life. Moreover, compared to controls without pulp, the pulp of acai increased the content of mono and polyunsaturated fatty acids and the production of α- linolenic acid (ALA) and conjugated linoleic acid (CLA) in nonfat yogurt co-fermented with B. animalis ssp. lactis strains Bl04 and B94. All fibers were able to increase the concentration of short chain fatty acids and polyunsaturated fats in yogurt, but only the apple and banana fibers increased the viability of probiotic bacteria during shelf life compared to controls without fiber. We observed a synergistic effect between the type of fiber and probiotic on the CLA content. On the other hand, the amount of ALA was significantly increased by the addition of banana fiber, regardless of the probiotic strain used. The passion fruit fiber promoted an increase CLA in all probiotic yoghurts. The results point out the applicability of adding whether açai or apple, banana or passion fruit byproducts in the formulation of probiotic yoghurts to improve the fatty acids profile and to uphold the desirable probiotic counts during four weeks of cold storage. In addition, the passion fruit fiber helped to enhance the texture parameters in skim yoghurts co-fermented by bifidobacteria.
190

Estudo da microestrutura e dinâmica molecular do Poly(3-(2\'-ethylhexyl)thiophene)(P3EHT) via ressonância magnética nuclear / Study of the microstructure and molecular dynamics of Poly(3-(2\'-ethylhexyl)thiophene)(P3EHT) by nuclear magnetic resonance

Cunha, Giovanni Paro da 18 April 2016 (has links)
O estudo da microestrutura e dinâmica molecular de polímeros conjugados é de grande importância para o entendimento das propriedades físicas desta classe de materiais. No presente trabalho utilizou-se técnicas de ressonância magnética nuclear em baixo e alto campo para elucidar os processos de dinâmica molecular e cristalização do polímero Poly(3-(2’-ethylhexyl)thiophene) - P3EHT. O P3EHT é um polímero modelo para tal estudo, pois apresenta temperatura de fusão bem inferior a sua temperatura de degradação. Esta característica permite acompanhar os processos de cristalização in situ utilizando RMN. Além disso, sua similaridade ao já popular P3HT o torna um importante candidato a camada ativa em dispositivos eletrônicos orgânicos. O completo assinalamento do espectro de 13C para o P3EHT foi realizado utilizando as técnicas de defasamento dipolar e HETCOR. Os processos de dinâmica molecular, por sua vez, foram sondados utilizando DIPSHIFT. Observou-se um gradiente de mobilidade na cadeia lateral do polímero. Além disso, os baixos valores de parametros de ordem obtidos em comparação a experimentos similares realizados no P3HT na literatura indicam um aparente aumento no volume livre entre cadeias consecutivas na fase cristalina. Isso indica que a presença do grupo etil adicional no P3EHT causa um completo rearranjo das moléculas e dificulta seu empacotamento. Constatou-se ainda pouca variação das curvas de DIPSHIFT para os carbonos da cadeia lateral como função do método de excitação utilizado, o que aponta para um polímero que apresenta cadeia lateral móvel mesmo em sua fase cristalina. Os dados de dinâmica molecular foram corroborados por medidas de T1, T1ρ e TCH. Utilizando filtros dipolares em baixo campo observou-se três temperaturas de transição para o P3EHT: 250 K, 325 K e 350 K. A cristalização desse material é um processo lento. Verificou-se que o mesmo pode se estender por até até 24h a temperatura ambiente. Mudanças no espectro de 13C utilizando CPMAS em alto campo indicam um ordenamento dos anéis tiofeno (empacotamento π – π) como o principal processo de cristalização para o P3EHT. / The study of the microstructure and molecular mobility of conjugated polymers is of the utmost importance for the understanding of the physical properties of this class of materials. In the current work we employed nuclear magnetic resonance techniques to shed light into the processes of molecular dynamics and crystallization of the polymer Poly(3-(2’-ethylhexyl)thiophene) - P3EHT. The P3EHT is a model polymer for such a study since it displays a melting temperature well below it’s degradation temperature, this allowed us to probe the crystallization process in situ using NMR. Furthermore it’s similarity to the already popular P3HT makes it a good candidate to active layer in organic electronic devices. A complete assignment of the 13C spectrum was achieved for the P3EHT, using the dipolar dephasing and HETCOR techniques. The molecular movements were probed by DIPSHIFT. We observed a mobility gradient along the side-chain of the material. The low values obtained for the order parameter in comparison to similar experiments done on the P3HT on the literature indicate a apparent increase in the free volume between consecutive chains in the crystalline phase, this is a strong indicative that the addition of the ethyl group to the repetitive unit strongly rearranges the molecules, difficulting packing. Moreover the depth of the DIPSHIFT curves for the side-chain carbons at half the rotor period don’t seem to be a function of the excitation method employed, this points to a polymer that is throughout mobile, i.e. that has carbons with a high degree of mobility even in it’s crystalline phase. This results were corroborated by measurements of T1, T1ρ e TCH. Employing dipolar filters at low field three transition temperatures were observed: 250 K, 325 K and 350K. The crystallization of the P3EHT is a slow process. We found that it took up to 24h for the material to fully recrystallize from the melting at room temperature. Changes in the 13C CPMAS spectra at high fields indicate a ordering of the thiophene rings (π – π stacking) as the primary method for the crystallization in the P3EHT.

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