Polymers are subjected to physical and chemical changes during their processing, service life, and further recovery, and they may also interact with impurities that can alter their composition. These changes substantially modify the stabilisation mechanisms and mechanical properties of recycled polymers. Detailed knowledge about how the different stages of their life cycle affect the degree of degradation of polymeric materials is important when discussing their further waste recovery possibilities and the performance of recycled plastics. A dual-pronged experimental approach employing multiple processing and thermo-oxidation has been proposed to model the life cycle of recycled high-impact polystyrene (HIPS). Both reprocessing and thermo-oxidative degradation are responsible for coexistent physical and chemical effects (chain scission, crosslinking, apparition of oxidative moieties, polymeric chain rearrangements, and physical ageing) on the microstructure and morphology of polybutadiene (PB) and polystyrene (PS) phases; these effects ultimately influence the long-term stability, and the rheological and mechanical behaviour of HIPS. The PB phase has proved to be the initiation point of HIPS degradation throughout the life cycle. Thermo-oxidation seems to have more severe effects on HIPS properties; therefore, it can be concluded that previous service life may be the part of the life cycle with the greatest influence on the recycling possibilities and performance of HIPS recyclates in second-market applications. The results from the life cycle degradation simulation were compared with those obtained from real samples from a large-scale mechanical recycling plant. A combination of different analytical strategies (thermal analysis, vibrational spectroscopy, and chromatographic analysis) is necessary to obtain a detailed understanding of the quality of recycled HIPS as defined by three key properties: degree of mixing, degree of degradation, and presence of low molecular weight compounds. / QC 20101119

Interfaces play a crucial role in the exchange of energy and matter in various physical, chemical and biological systems. A particular interest has been to study interfaces between aqueous phases and various minerals because of their importance in understanding geochemical phenomena as well as for applications such as enhanced oil recovery. The nonlinear optical technique of vibrational sum-frequency generation (SFG) spectroscopy, introduced over 20 years ago, has become a powerful tool to investigate various surfaces, in particular, mineral-water interfaces. One of the challenges of the SFG spectroscopy of aqueous surfaces is the need to tune the central frequency of relatively narrowband IR lasers through the broad range of the OH-stretch frequencies of water molecules (3000 - 4000 cm-1). We have developed a novel ultrabroadband IR laser source that generates infrared pulses in the ~2800-6000 cm-1 range (lambda~3300-1800 nm) with bandwidths Delta(nu)>1000 cm-1, and bandwidths >2000 cm-1 in the near-IR range (lambda~1000-2000 nm). Pulse front tilt of signal pulse has been corrected allowing for compression of signal pulses down to 25 fsec. Such ultrabroadband IR pulses allow us to perform SFG spectroscopy of aqueous surfaces over the entire frequency range of water molecule spectrum (extending from ~2900 cm -1 to ~3800 cm -1) simultaneously, without tuning the laser ("in one shot"). We have used this novel ultrabroadband IR source to investigate the vibrational SFG spectra of silica/water interfaces. The high signal-to-noise ratio of our spectroscopic setup has allowed us to study low-intensity features that were not studied in detail, or recognized previously in the SFG-spectroscopy investigations, including: 1) non-hydrogen bonded OH vibrations at hydrophilic silica/water interfaces; 2) combination [stretch+bend] bands of water at the silica surface appearing at ~5000-5200 cm -1. 3) Overtones of water stretching modes at silica/water interfaces. The most important conclusions from these studies are outlined below. 1. Non-hydrogen bonded hydroxyls at silica/water interface. Typically SFG-studies of mineral/water interfaces (in particular, silica/water) have focused on the most pronounced features - peaks of H-bonded hydroxyls at ~3150 and ~3450 cm -1. We have been able to systematically observe and study a weaker peak at ~3670 - 3700 cm -1. This peak becomes more pronounced as the pH of aqueous phase decreases, as well as the ionic strength increases, indicating that the hydroxyls corresponding to this spectral feature are situated in a very close proximity to the surface. Isotopic dilution experiments indicate that the 3700 cm -1 feature is not due to asymmetric OH stretches as was suggested before. Based on our results, we suggest that this spectral feature corresponds to hydroxyls of water molecules at the silica surface that cannot hydrogen bond with silanol groups because of the lower density of silanols compared to H2O. We believe this to be the first surface-specific study of non-hydrogen bonded hydroxyls at silica, a surface widely accepted as hydrophilic. 2. SFG spectroscopy of [ν(OH)+δ(HOH)] combination bands of water at silica surface. We have extended SFG spectroscopy of the interfacial hydroxyls at mineral/water surfaces into the near-IR frequency range. The studies of overtones of interfacial OH(OD) groups will provide information on the anharmonicity of such species, and thus on the energy of dissociation. In addition, the positions of the overtone frequencies of the hydroxyls are more sensitive to interactions with the environment than the fundamental stretch frequencies. Our particular focus has been to study the stretch+bend combination band nu comb nu;(OH)+delta;(HOH) of liquid water which occurs in the near-IR spectral range at ~5000-5200 cm -1. It is typically much weaker in the FTIR absorption spectra than the fundamental transitions of the OH stretches or HOH bending, similar to overtones of these modes. We have performed, what we believe to be, the first surface-specific vibrational SFG spectroscopic measurements of combination bands of water molecules at silica surfaces. SFG spectroscopy of water combination band allows access to the water bending mode (delta~1600 cm -1), which still has not been observed in sum-frequency. / Chemistry

Diese Arbeit ermöglicht ein detailliertes Verständnis der Schwingungsdynamik und Kupplungen in einem Basenpaar-Modellsystem und in künstlichen DNA-Oligomeren bei verschiedenen Hydratationsgraden. Durch die Verwendung von nichtlinearer ultraschneller IR Pump-Probe Spektroskopie sind die Schwingungsbewegungen hydratisierter DNA und die schnellsten Veränderungen in den DNA-Wasser-Wechselwirkungen und Hydrationsgeometrien direkt zugänglich. 2-pyridone/2-hydroxypyridine ist ein Modellsystem für die gekoppelte intermolekularen Wasserstoffbrücken, deren Struktur der von DNA-Basenpaaren ähnelt. In Dichlormethan existiert das Molekül als ein zyklischer 2-Pyridon-Dimer, deren Vorkommern durch NMR-und 2D-FTIR Spektroskopie verifiziert wurde. Die beobachteten kohärente Oszillationen aufgrund niederfrequenter Wellenpaketbewegungen der Dimere können für die Dynamik und räumliche Geometrie der Basenpaare in den DNA-Molekül relevant sein. Transiente Schwingungsspektren eines poly[d(A-T)]:poly[d(A-T)] Film erlauben die Zuordnung von verschiedenen NH-Streckbanden zu einer bestimmten Schwingung der Nukleinbasen und ermöglichen deren Abgrenzung zu den Beiträgen von OH-Streckschwingungen des umgebenden Wassers. Bei einem niedrigen Hydratisierungsgrad verändern die restlichen, an die Phosphatgruppen gebundenen Wassermoleküle, ihre Ausrichtung auf ultraschnellen Zeitskalen nicht. Im Fall vollständig hydratisierter DNA ist die Dynamik der Wasserhülle dem Verhalten des reinen Wassers ähnlicher und man beobachtet spektrale Diffusion der OH-Streckschwingung im Subpikosekundenbereich sowie einen Zerfall der Schwingungsanisotropie durch Molekülrotation und/oder Energietransfer. Die Wassermoleküle der Phosphat-Hydratationshülle dienen als effiziente Wärmesenke für Überschussenergie aus der DNA, wobei die Energietransferzeiten im fs-bereich liegen. Im Gegensatz dazu erfolgt Energietransport innerhalb der DNA auf einer langsameren Zeitskala von 20 ps. / This thesis provides a detailed understanding of vibrational dynamics and couplings in a base pair model system and artificial DNA oligomers at different levels of hydration. By using nonlinear ultrafast infrared pump-probe spectroscopy, the basic vibrational motions of hydrated DNA and the fastest changes in the DNA–water interactions and hydration geometries are directly accessed. 2-pyridone/2-hydroxypyridine is used as a model molecule for coupled intermolecular hydrogen bonds with a structure resembling a DNA base pair. In dichloromethane the molecule predominantly exists as a cyclic 2-pyridone dimer as determined using a combined NMR and 2D FTIR approach. The observed coherent oscillations due to low-frequency hydrogen bond wavepacket motions of the dimers are expected to be relevant for the dynamics and spatial geometry of base pairs in DNA molecule. Transient vibrational spectra of a poly[d(A-T)]:poly[d(A-T)] film enabled the assignment of different NH stretching bands to particular nucleobase vibrations, also discerning them from the OH stretching contributions of the surrounding water. At a low hydration level, residual water molecules, bound to the phosphate groups, do not alter their orientation on ultrafast time scales. In the case of fully hydrated DNA, the dynamics of the water shell are closer to those of bulk liquid water with a sub-picosecond spectral diffusion and a loss of vibrational anisotropy as a result of molecular rotation and/or energy transfer. The water shell around the phosphates serves as a efficient heat sink accepting excess energy from DNA in a femtosecond time domain, whereas the energy transfer within DNA occurs on the time scale of 20 ps.

<p dir="ltr">Interest in proteins has expanded beyond biology. Proteins have found use in fields as varied as lanthanide separation, solar cell technology, medicine and fluorescent dyes. To develop proteins for each of these applications, it is necessary to understand each protein's structure. Through understanding the structure we are able to either improve that protein's function or design materials to target and inhibit its function. To this end, it is necessary to be able to screen a protein's structure and to study the protein's function in a quick and efficient manner. Spectroscopic techniques are able to fill this gap due to their low material requirements. To fully take advantage of the small sample size requirements of these techniques, this thesis reports on the development of a set of small-volume methods that need minimal material and are compatible with a wide range of instrumentation.</p>

O uso de materiais orgânicos em dispositivos eletrônicos, além de menor custo e facilidade de processamento, permite obter flexibilidade e transparência. Entretanto, para que a aplicação comercial desses materiais seja viável, os processos que ocorrem nos dispositivos ainda precisam ser mais bem compreendidos, visando maior eficiência e tempo de vida. É de grande importância o estudo das interfaces entre o semicondutor orgânico e os contatos metálicos, onde ocorre transferência de portadores de carga, e a interface com o dielétrico em transistores orgânicos (OFETs), onde se forma o canal de condução. As interfaces de dispositivos eletrônicos poliméricos foram estudadas, utilizando-se Espectroscopia SFG (do inglês Sum Frequency Generation). Esta técnica obtém um sinal com a soma das frequências de dois feixes incidentes sobrepostos, em um processo seletivo a meios onde não há simetria de inversão, como no caso de interfaces. Com aplicação de um feixe de excitação na região visível e outro sintonizável no infravermelho médio, a espectroscopia SFG fornece um espectro vibracional da interface e permite o estudo do ordenamento e da orientação dos grupos moleculares. Foram construídos e analisados OFETs de poli-3-hexiltiofeno (P3HT) preparados sobre substrato de vidro ou silício, utilizando como isolante óxido de silício e/ou poli-metil-metacrilato (PMMA). Foram obtidos espectros in situ do canal de OFETs em operação, observando pequenas alterações na forma de linha, porém a baixa relação sinal/ruído não permitiu obter conclusões detalhadas. Foi constatada a manifestação de bandas da camada isolante de PMMA como consequência da aplicação de campo elétrico. Este fenômeno foi considerado como uma nova ferramenta para estudar a distribuição de cargas e campo elétrico no canal de transistores. Não foram detectados sinais de degradação irreversível no polímero semicondutor a curto prazo, e a mudança de comportamento elétrico foi atribuída majoritariamente a dopagem por oxigênio absorvido no material. / The usage of organic materials in electronic devices allows not only low cost and ease of processing but also flexibility and transparency. However, to achieve viable commercial application, the processes involved on the devices operation must still be better comprehended, aiming for improved efficiency and life time. There is great importance in the study of the interfaces between organic semiconductors and metallic contacts, where charge transfer takes place, and between the dielectric and semiconductor layers of organic transistors (OFETs), where the conducting channel is formed. The interfaces in polymeric electronic devices were studied by SFG spectroscopy (Sum Frequency Generation). In this technique, a signal with frequency that equals the sum of those of two incident beams is generated in a process only allowed in media without inversion symmetry, such as interfaces. Using a visible excitation beam and a tunable infrared one, SFG spectroscopy yields a vibrational spectrum of the interface and provides information about the conformation and orientation of molecular groups. Poly-3-hexylthiophene (P3HT) OFETs were fabricated using glass or silicon substrates and silicon oxide and/or poly-methyl-methacrylate (PMMA) for the dielectric layer. SFG spectra were acquired in situ from the channel region of operating OFETs, observing small changes in lineshape, but low signal-to-noise ration did not allow a detailed interpretation. It was found that PMMA vibrational bands appeared when polarizing the device. This phenomenon was considered a new tool for studying the electric field and charge distribution along transistor channels. It was not noted any sign of short term irreversible degradation of the semiconducting polymer, and the change in the electrical behavior was attributed mainly to doping of the polymer by oxygen absorbed in the material.

O uso de materiais orgânicos em dispositivos eletrônicos, além de menor custo e facilidade de processamento, permite obter flexibilidade e transparência. Entretanto, para que a aplicação comercial desses materiais seja viável, os processos que ocorrem nos dispositivos ainda precisam ser mais bem compreendidos, visando maior eficiência e tempo de vida. É de grande importância o estudo das interfaces entre o semicondutor orgânico e os contatos metálicos, onde ocorre transferência de portadores de carga, e a interface com o dielétrico em transistores orgânicos (OFETs), onde se forma o canal de condução. As interfaces de dispositivos eletrônicos poliméricos foram estudadas, utilizando-se Espectroscopia SFG (do inglês Sum Frequency Generation). Esta técnica obtém um sinal com a soma das frequências de dois feixes incidentes sobrepostos, em um processo seletivo a meios onde não há simetria de inversão, como no caso de interfaces. Com aplicação de um feixe de excitação na região visível e outro sintonizável no infravermelho médio, a espectroscopia SFG fornece um espectro vibracional da interface e permite o estudo do ordenamento e da orientação dos grupos moleculares. Foram construídos e analisados OFETs de poli-3-hexiltiofeno (P3HT) preparados sobre substrato de vidro ou silício, utilizando como isolante óxido de silício e/ou poli-metil-metacrilato (PMMA). Foram obtidos espectros in situ do canal de OFETs em operação, observando pequenas alterações na forma de linha, porém a baixa relação sinal/ruído não permitiu obter conclusões detalhadas. Foi constatada a manifestação de bandas da camada isolante de PMMA como consequência da aplicação de campo elétrico. Este fenômeno foi considerado como uma nova ferramenta para estudar a distribuição de cargas e campo elétrico no canal de transistores. Não foram detectados sinais de degradação irreversível no polímero semicondutor a curto prazo, e a mudança de comportamento elétrico foi atribuída majoritariamente a dopagem por oxigênio absorvido no material. / The usage of organic materials in electronic devices allows not only low cost and ease of processing but also flexibility and transparency. However, to achieve viable commercial application, the processes involved on the devices operation must still be better comprehended, aiming for improved efficiency and life time. There is great importance in the study of the interfaces between organic semiconductors and metallic contacts, where charge transfer takes place, and between the dielectric and semiconductor layers of organic transistors (OFETs), where the conducting channel is formed. The interfaces in polymeric electronic devices were studied by SFG spectroscopy (Sum Frequency Generation). In this technique, a signal with frequency that equals the sum of those of two incident beams is generated in a process only allowed in media without inversion symmetry, such as interfaces. Using a visible excitation beam and a tunable infrared one, SFG spectroscopy yields a vibrational spectrum of the interface and provides information about the conformation and orientation of molecular groups. Poly-3-hexylthiophene (P3HT) OFETs were fabricated using glass or silicon substrates and silicon oxide and/or poly-methyl-methacrylate (PMMA) for the dielectric layer. SFG spectra were acquired in situ from the channel region of operating OFETs, observing small changes in lineshape, but low signal-to-noise ration did not allow a detailed interpretation. It was found that PMMA vibrational bands appeared when polarizing the device. This phenomenon was considered a new tool for studying the electric field and charge distribution along transistor channels. It was not noted any sign of short term irreversible degradation of the semiconducting polymer, and the change in the electrical behavior was attributed mainly to doping of the polymer by oxygen absorbed in the material.

Apesar de ser utilizado há muito tempo como solvente para espécies orgânicas e inorgânicas, bem como carreador de fármacos, muitos aspectos relativos à auto-associação intermolecular do dimetil sulfóxido (DMSO) e às suas interações com espécies iônicas são ainda motivos de controvérsia na literatura. No presente estudo, a estrutura e ambiente local de dimetil sulfóxido (DMSO) em diferentes meios iônicos foram estudados por meio de três abordagens diferentes. Na primeira abordagem, o efeito de não-coincidência Raman (NCR) observado na banda atribuída ao modo &#957;(S=O) do DMSO, ca. 1050 cm-1, foi investigado para o líquido puro e em soluções de tetracloreto de carbono (CCl4) e água. Além disso, foi investigado o efeito de espécies iônicas (Kl, KSCN, KBr, TBAN3, TBAOCN, LiClO4, Mg(ClO4)2) na frequência &#957;(S=O), bem como no NCR das soluções. Os resultados de NCR juntamente com as técnicas de infravermelho, RMN e de medidas de propriedades físico-químicas mostraram que essas espécies iônicas não somente afetam a estrutura de associação do DMSO, como são capazes de interagir fortemente com o solvente. Na segunda abordagem, com a finalidade de modular as propriedades de um líquido iônico, fez-se a análise estrutural das misturas envolvendo DMSO e água como solventes e o líquido iônico EAN como soluto por meio das técnicas de espalhamento de raios-X e de nêutrons. Os resultados mostraram que a estrutura cátion-ânion do EAN é afetada pela presença de DMSO e, que em ambos os solventes são evidentes fortes ligações de hidrogênio entre o cátion EA+ e os oxigênios do solvente e do ânion nitrato. As moléculas de água não afetam drasticamente a estrutura do EAN, pois seu caráter doador/aceptor de LH e seu tamanho permite a formação de pontes entre cátion e o ânion, no entanto, EAN consegue distorcer a rede tridimensional de ligação de hidrogênio da água. Por outro lado, as moléculas de DMSO afastam os ânions da região polar do EA+ na competição pela formação de LH com o cátion e o EAN, por sua vez, provoca a ruptura das estruturas de associação do DMSO. Na terceira abordagem, misturas envolvendo três diferentes SEPs (uma classe de líquidos iônicos); Relina, MUCHCl e DMUCHCl; com DMSO foram investigadas por meio de suas propriedades físico-químicas e por espectroscopia Raman, tendo em vista modular as propriedades dos SEPs. Neste caso, os resultados não apontaram para interações fortes e específicas envolvendo as espécies iônicas e o DMSO, mas a um maior empacotamento do sistema, onde os desvios de suas propriedades físico-químicas com relação à idealidade são negativos e sua mobilidade iônica juntamente com a análise dos espectros vibracionais não evidenciaram interações específicas. No entanto, as viscosidades e densidades diminuíram nas misturas e a mobilidade iônica foi favorecida. / Although it has long been used as a solvent for organic and inorganic species, as well as drug carriers, many aspects concerning the intermolecular self-association of dimethyl sulfoxide (DMSO) and their interactions with ionic species are still controversial in the literature. In the present study, the structure and local environment of dimethyl sulfoxide (DMSO) in different ionic media were studied using three different approaches. In the first approach, the Raman non-coincidence effect (NCE) observed in the band assigned to the DMSO &#957;(S = O) mode, ca. 1050 cm-1, was investigated for the pure liquid and in its solutions of carbon tetrachloride (CCl4) and water. In addition, the effect of ionic species (K1, KSCN, KBr, TBAN3, TBAOCN, LiClO4, Mg (ClO4)2) on the frequency &#957;(S = O) as well as the NCE of the solutions were investigated. The results of NCR together with the infrared, NMR and physico-chemical properties measurements showed that these ionic species not only affect the association structure of DMSO, but are also capable of interacting strongly with the solvent. In the second approach, with the purpose of modulating the properties of an ionic liquid, the structural analysis of the mixtures involving DMSO and water as solvents and the ionic liquid EAN as a solute were carried out by X-ray and neutron scattering techniques. The results showed that the cation-anion structure of the EAN is affected by the presence of DMSO and that in both solvents strong hydrogen bonds between the EA+ cation and the oxygen from solvent and from nitrate anion are evident. The water molecules do not affect the structure of the EAN drastically, because its LH donor/acceptor character and its size allows the formation of bridges between cation and anion, however, EAN can distort the hydrogen bonding three-dimensional network in water. On the other hand, the DMSO molecules repels the anions from the polar head of EA+ in the competition in forming LH with the cation, however EAN break down DMSO association structures. In the third approach, mixtures involving three different SEPs (a class of ionic liquids); Relina, MUCHCl and DMUCHCl; with DMSO were investigated by means of their physicochemical properties and by Raman spectroscopy, in order to modulate the properties of SEPs. In this case, the results did not point to strong and specific interactions involving the ionic species and DMSO, but to a greater packaging of the system, where the deviations of its physicochemical properties with respect to the ideality are negative and its ionic mobility together with the analysis of the vibrational spectra showed no specific interactions. However, the viscosities and densities decreased in the mixtures and the ionic mobility was favored.

Apesar de ser utilizado há muito tempo como solvente para espécies orgânicas e inorgânicas, bem como carreador de fármacos, muitos aspectos relativos à auto-associação intermolecular do dimetil sulfóxido (DMSO) e às suas interações com espécies iônicas são ainda motivos de controvérsia na literatura. No presente estudo, a estrutura e ambiente local de dimetil sulfóxido (DMSO) em diferentes meios iônicos foram estudados por meio de três abordagens diferentes. Na primeira abordagem, o efeito de não-coincidência Raman (NCR) observado na banda atribuída ao modo &#957;(S=O) do DMSO, ca. 1050 cm-1, foi investigado para o líquido puro e em soluções de tetracloreto de carbono (CCl4) e água. Além disso, foi investigado o efeito de espécies iônicas (Kl, KSCN, KBr, TBAN3, TBAOCN, LiClO4, Mg(ClO4)2) na frequência &#957;(S=O), bem como no NCR das soluções. Os resultados de NCR juntamente com as técnicas de infravermelho, RMN e de medidas de propriedades físico-químicas mostraram que essas espécies iônicas não somente afetam a estrutura de associação do DMSO, como são capazes de interagir fortemente com o solvente. Na segunda abordagem, com a finalidade de modular as propriedades de um líquido iônico, fez-se a análise estrutural das misturas envolvendo DMSO e água como solventes e o líquido iônico EAN como soluto por meio das técnicas de espalhamento de raios-X e de nêutrons. Os resultados mostraram que a estrutura cátion-ânion do EAN é afetada pela presença de DMSO e, que em ambos os solventes são evidentes fortes ligações de hidrogênio entre o cátion EA+ e os oxigênios do solvente e do ânion nitrato. As moléculas de água não afetam drasticamente a estrutura do EAN, pois seu caráter doador/aceptor de LH e seu tamanho permite a formação de pontes entre cátion e o ânion, no entanto, EAN consegue distorcer a rede tridimensional de ligação de hidrogênio da água. Por outro lado, as moléculas de DMSO afastam os ânions da região polar do EA+ na competição pela formação de LH com o cátion e o EAN, por sua vez, provoca a ruptura das estruturas de associação do DMSO. Na terceira abordagem, misturas envolvendo três diferentes SEPs (uma classe de líquidos iônicos); Relina, MUCHCl e DMUCHCl; com DMSO foram investigadas por meio de suas propriedades físico-químicas e por espectroscopia Raman, tendo em vista modular as propriedades dos SEPs. Neste caso, os resultados não apontaram para interações fortes e específicas envolvendo as espécies iônicas e o DMSO, mas a um maior empacotamento do sistema, onde os desvios de suas propriedades físico-químicas com relação à idealidade são negativos e sua mobilidade iônica juntamente com a análise dos espectros vibracionais não evidenciaram interações específicas. No entanto, as viscosidades e densidades diminuíram nas misturas e a mobilidade iônica foi favorecida. / Although it has long been used as a solvent for organic and inorganic species, as well as drug carriers, many aspects concerning the intermolecular self-association of dimethyl sulfoxide (DMSO) and their interactions with ionic species are still controversial in the literature. In the present study, the structure and local environment of dimethyl sulfoxide (DMSO) in different ionic media were studied using three different approaches. In the first approach, the Raman non-coincidence effect (NCE) observed in the band assigned to the DMSO &#957;(S = O) mode, ca. 1050 cm-1, was investigated for the pure liquid and in its solutions of carbon tetrachloride (CCl4) and water. In addition, the effect of ionic species (K1, KSCN, KBr, TBAN3, TBAOCN, LiClO4, Mg (ClO4)2) on the frequency &#957;(S = O) as well as the NCE of the solutions were investigated. The results of NCR together with the infrared, NMR and physico-chemical properties measurements showed that these ionic species not only affect the association structure of DMSO, but are also capable of interacting strongly with the solvent. In the second approach, with the purpose of modulating the properties of an ionic liquid, the structural analysis of the mixtures involving DMSO and water as solvents and the ionic liquid EAN as a solute were carried out by X-ray and neutron scattering techniques. The results showed that the cation-anion structure of the EAN is affected by the presence of DMSO and that in both solvents strong hydrogen bonds between the EA+ cation and the oxygen from solvent and from nitrate anion are evident. The water molecules do not affect the structure of the EAN drastically, because its LH donor/acceptor character and its size allows the formation of bridges between cation and anion, however, EAN can distort the hydrogen bonding three-dimensional network in water. On the other hand, the DMSO molecules repels the anions from the polar head of EA+ in the competition in forming LH with the cation, however EAN break down DMSO association structures. In the third approach, mixtures involving three different SEPs (a class of ionic liquids); Relina, MUCHCl and DMUCHCl; with DMSO were investigated by means of their physicochemical properties and by Raman spectroscopy, in order to modulate the properties of SEPs. In this case, the results did not point to strong and specific interactions involving the ionic species and DMSO, but to a greater packaging of the system, where the deviations of its physicochemical properties with respect to the ideality are negative and its ionic mobility together with the analysis of the vibrational spectra showed no specific interactions. However, the viscosities and densities decreased in the mixtures and the ionic mobility was favored.

Filmes de poli(fluoreto de vinilideno-co-trifluoretileno), P(VDF-IrFE), com uma razão molar 70/30 de VDF e IrFE, respectivamente, foram expostos à radiação-X sob vácuo em uma ampla faixa de doses de irradiação. Este é um copolímero estatístico e semi-cristalino que possui a especial característica de cristalizar espontaneamente numa estrutura ferroelétrica. Ele também possui uma transição de fase ferro-paraelétrica detectável, definida como a temperatura de Curie (Tc). Devido a estas características tem despertado considerável interesse, em especial na área da eletrônica como elemento transdutor. As modificações induzidas foram investigadas por espectroscopia fotoacústica no infravermelho (FT-IR/PAS), assim como FI-IR por transmitância, calorimetria exploratória diferencial (DSC), termogravimetria (IG), difração de raios-X, UV/Visível e espectroscopia Raman. As técnicas espectroscópicas vibracionais (fotoacústica no IR, Raman e absorção no IR) foram utilizadas na identificação de bandas relacionadas às regiões cristalinas e amorfas, formação e rompimento de ligações e presença de novos grupos funcionais. Nos espectros IR e Raman são observadas duas bandas que estão relacionadas às regiões cristalinas e sofrem mudanças nas suas intensidades relativas de acordo com a dose de radiação. Essas mudanças podem ser interpretadas como aumento ou diminuição do grau de cristalinidade, e também em termos de modificações de arranjos cristalinos. A difração de raio-X mostrou o aparecimento de um pico, próximo àquele da fase ferroelétrica, sob aumento da dose de radiação, devido a um processo de modificação do arranjo cristalino acima da dose de 480 kGy. Foi observado um aumento de intensidade no referido pico de difração, correspondendo a um aumento do grau de cristalinidade da amostra. As curvas de DSC mostraram picos endotérmicos correspondentes a fusão e transições de fases que, através de suas variações, possibilitam avaliar os efeitos da irradiação com raios-X. Os espectros UV/Visível mostraram absorções dos cromóforos cujas intensidades de banda aumentam com a dose de radiação e diminuem durante o envelhecimento da amostra. Os dados indicam que a radiação-X induz uma modificação no arranjo cristalino do P(VDF-TrFE). Tal modificação, é provavelmente uma mudança de estrutura ferroelétrica para outra, paraelétrica. / Poly(vinylidene fluoride-co-trifluoroethylene) films, P(VDF-TrFE), with a molar ratio 70/30 of VDF and TrFE units, respectively, were exposed to X-ray radiation under vacuum in a wide range of irradiation doses. This is a statistic semi-crystalline copolymer and displays the unique feature of a spontaneous crystallization into a ferroelectric structure. It also possesses a detectable ferro-paraelectric transition, the Curie temperature (Tc). Due to these characteristics considerable interest in such copolymer has been generated, specially in electronics as a transducer element. The induced modifications were investigated by Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) as well as transmittance FT-IR, differential scanning calorimetry (DSC), thermogravimetry (TG), X-ray diffraction, UV/Visible and Raman spectroscopies. The spectroscopic vibrational techniques (FT-IR/PAS, FT-IR and Raman) were used to identify bands related to crystalline and amorphous regions, bond formation, bond scission and presence of new functional groups. In both IR and Raman spectra were observed a couple of bands related to the crystalline regions that undergo changes of relative intensities with the radiation dose. These changes may be interpreted as an increase or decrease of the crystallinity degree, and also modifications of crystal structure. X-ray diffraction showed a new peak, close to that of the ferroelectric phase, under increasing radiation doses, due to a modification of crystal structure process above 480 kGy dose. An increase in the intensity of the former diffraction peak was observed, corresponding to an increase in the crystallinity degree. The DSC curves showed the endothermic peaks corresponding to the melting and the phase transitions, whose variations allow an evaluation of the effects of X-ray radiation. UV/Visible spectra showed chromophores absorptions whose band intensities increase by radiation dose and decrease during sample\'s aging. The data indicate that P(VDF-TrFE) under X-ray radiation exposition undergoes a crystal structure modification, probably a change of a ferroelectric structure to another one, paraelectric.

Filmes de poli(fluoreto de vinilideno-co-trifluoretileno), P(VDF-IrFE), com uma razão molar 70/30 de VDF e IrFE, respectivamente, foram expostos à radiação-X sob vácuo em uma ampla faixa de doses de irradiação. Este é um copolímero estatístico e semi-cristalino que possui a especial característica de cristalizar espontaneamente numa estrutura ferroelétrica. Ele também possui uma transição de fase ferro-paraelétrica detectável, definida como a temperatura de Curie (Tc). Devido a estas características tem despertado considerável interesse, em especial na área da eletrônica como elemento transdutor. As modificações induzidas foram investigadas por espectroscopia fotoacústica no infravermelho (FT-IR/PAS), assim como FI-IR por transmitância, calorimetria exploratória diferencial (DSC), termogravimetria (IG), difração de raios-X, UV/Visível e espectroscopia Raman. As técnicas espectroscópicas vibracionais (fotoacústica no IR, Raman e absorção no IR) foram utilizadas na identificação de bandas relacionadas às regiões cristalinas e amorfas, formação e rompimento de ligações e presença de novos grupos funcionais. Nos espectros IR e Raman são observadas duas bandas que estão relacionadas às regiões cristalinas e sofrem mudanças nas suas intensidades relativas de acordo com a dose de radiação. Essas mudanças podem ser interpretadas como aumento ou diminuição do grau de cristalinidade, e também em termos de modificações de arranjos cristalinos. A difração de raio-X mostrou o aparecimento de um pico, próximo àquele da fase ferroelétrica, sob aumento da dose de radiação, devido a um processo de modificação do arranjo cristalino acima da dose de 480 kGy. Foi observado um aumento de intensidade no referido pico de difração, correspondendo a um aumento do grau de cristalinidade da amostra. As curvas de DSC mostraram picos endotérmicos correspondentes a fusão e transições de fases que, através de suas variações, possibilitam avaliar os efeitos da irradiação com raios-X. Os espectros UV/Visível mostraram absorções dos cromóforos cujas intensidades de banda aumentam com a dose de radiação e diminuem durante o envelhecimento da amostra. Os dados indicam que a radiação-X induz uma modificação no arranjo cristalino do P(VDF-TrFE). Tal modificação, é provavelmente uma mudança de estrutura ferroelétrica para outra, paraelétrica. / Poly(vinylidene fluoride-co-trifluoroethylene) films, P(VDF-TrFE), with a molar ratio 70/30 of VDF and TrFE units, respectively, were exposed to X-ray radiation under vacuum in a wide range of irradiation doses. This is a statistic semi-crystalline copolymer and displays the unique feature of a spontaneous crystallization into a ferroelectric structure. It also possesses a detectable ferro-paraelectric transition, the Curie temperature (Tc). Due to these characteristics considerable interest in such copolymer has been generated, specially in electronics as a transducer element. The induced modifications were investigated by Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) as well as transmittance FT-IR, differential scanning calorimetry (DSC), thermogravimetry (TG), X-ray diffraction, UV/Visible and Raman spectroscopies. The spectroscopic vibrational techniques (FT-IR/PAS, FT-IR and Raman) were used to identify bands related to crystalline and amorphous regions, bond formation, bond scission and presence of new functional groups. In both IR and Raman spectra were observed a couple of bands related to the crystalline regions that undergo changes of relative intensities with the radiation dose. These changes may be interpreted as an increase or decrease of the crystallinity degree, and also modifications of crystal structure. X-ray diffraction showed a new peak, close to that of the ferroelectric phase, under increasing radiation doses, due to a modification of crystal structure process above 480 kGy dose. An increase in the intensity of the former diffraction peak was observed, corresponding to an increase in the crystallinity degree. The DSC curves showed the endothermic peaks corresponding to the melting and the phase transitions, whose variations allow an evaluation of the effects of X-ray radiation. UV/Visible spectra showed chromophores absorptions whose band intensities increase by radiation dose and decrease during sample\'s aging. The data indicate that P(VDF-TrFE) under X-ray radiation exposition undergoes a crystal structure modification, probably a change of a ferroelectric structure to another one, paraelectric.