Drug delivery to the nasal and ocular mucosa faces several obstacles. One of these is from the effective clearance mechanisms present in the nose and eye. Polymer gels with suitable rheological properties can facilitate the absorption of poorly absorbed drugs by increasing the contact time of the drug with the mucosa. This has been attributed to the rheological and mucoadhesive properties of the gel. The main objective of this thesis was to investigate the importance of these features for the anticipated in vivo contact time, here exemplified by the ocular and nasal routes of administration. The in situ gelling polymer gellan gum was found to have a favourable rheological and in vivo performance. When administered in the nasal cavity of rats, a gel was formed that could remain at the site of administration for up to 4 hours. In addition, the epithelial uptake and transfer of a 3 kDa fluorescein dextran was higher than for a mannitol solution. Therefore, it was concluded that a gellan gum formulation should be a promising strategy for nasal drug delivery. The potential mucoadhesive properties of a variety of polymer gels were investigated using a rheological method and by measuring the tensile force required to detach the gel from a mucosa. With both methods the rheological properties of the gel were a determining factor for the results obtained. The rheological method was found to have several limitations. One of these was that a positive response, interpreted as mucoadhesion, was only seen with weak gels. The tensile method could, in contrast, detect strengthening of the mucus only for strong gels. However, this method reflects the in vivo performance of the gel better than the rheological method. Finally, dielectric spectroscopy was explored as a tool for investigating the likelihood of intimate surface contact between the gel and the mucus layer. This novel approach involved determining the ease with which a charged particle can pass the gel-mucus interface layer, and may enable the study of the events at the interface closer to the molecular level, than is possible with the rheological and tensile strength methods.

This thesis concerns partial discharge (PD) diagnostics withvariable frequency of applied voltage in the frequency range 1mHz - 400 Hz. The exploration of a new type of spectroscopythat combines partial discharge analysis and dielectricresponse is demonstrated. A question addressed is if and howthe PD activity varies with the frequency of the appliedvoltage. The nature of an existing frequency dependence couldbe useful in the classification of different defects and tojudge the degree of progressive ageing. A Variable-Frequency Phase Resolved Partial DischargeAnalysis (VF-PRPDA) technique is developed for the appliedvoltage frequency range 1 mHz - 400 Hz. The VF-PRPDA techniqueis combined with a system for high voltage dielectricspectroscopy that allows simultaneous measurements. TheVF-PRPDA technique is used for studying the frequencydependence of PD. The PD activity is for example measured byintegrated measures like total charge per cycle and totalnumber of discharges per cycle. Statistical measures like mean,standard deviation, skewness, kurtosis etc. are applied tomeasure the frequency dependence of the phasedistributions. High voltage dielectric spectroscopy is supplemented withharmonic analysis for studying non-linear dielectric responsecurrents. The VF-PRPDA technique is demonstrated on defined objectslike point-plane gaps and artificial voids, but also on aninsulated stator bar and a paper insulated cable. Surfacedischarges on insulating surfaces are studied in an environmentwith a controlled relative humidity and temperature. Theadsorption of moisture on the insulating surface alters thesurface conductivity of the surface and the frequencydependence of the PD activity. The influence of temperature upon the PD activity is studiedfor a oil paper insulated cable. The results of the measurements show that the partialdischarge activity in general is frequency dependent over thefrequency range 1 mHz - 400 Hz. The reasons behind thefrequency dependence are linked to surface- and bulk-conducting mechanisms, frequency dependent field distributionsand statistical effects of the supply of start electrons. An algorithm is developed that relates the phase resolved PDcurrent measured with the PRPDA technique to the non-linearcurrent measured with dielectric spectroscopy. The algorithm isexperimentally verified by simultaneous measurements of PRPDAand dielectric spectroscopy on defined objects. The resultsexplain the contribution of PD to the apparent capacitance andloss. Moreover, the harmonics of the fundamental currentcomponent yield information about, for example, polaritydependent discharge sources. Keywords:diagnostic methods, partial discharges, phaseresolved, variable frequency, dielectric spectroscopy,dielectric response, harmonics, insulation / QC 20100527

Šiame darbe nagrinėjamos galimybės patobulinti plačiajuostės dielektrinės spektroskopijos metodus naudojant skaitmeninius ir analitinius daugelio modų dielektrinės skvarbos skaičiavimo metodus, tiriami (1-x)(Na1/2 Bi1/2)TiO3 - xLa(Mg1/2 Ti1/2)O3 (NBT-LMT) keramikų grupės laidumo ypatumai. Nagrinėjama galimybė pritaikyti HFSS skaitmeninio modeliavimo programą dielektrinės spektroskopijos tikslams. Naudojant šią programinę įrangą, apskaičiuojama dielektrinė ir magnetinė skvarbos komplikuotiems mikrojuostelinės linijos ir dalinai užpildyto bangolaidžio matavimo grandinių atvejams. Pateikiami patobulinti kondensatoriaus koaksialinėje linijoje ir ribotų matmenų atviro galo koaksialinės linijos matematiniai modeliai. Šie modeliai patikrinami skaitmeniniu metodu. Naudojant daugiamodį kondensatoriaus modelį, atsižvelgus į magnetinio lauko pasiskirstymą koaksialinėje matavimo grandinėje, pasiūlomas būdas pamatuoti mažai bandinio magnetinei skvarbai, kai dielektrinė skvarba didelė (dešimtim ar šimtais kartų didesnė už magnetinę skvarbą). Atviro galo koaksialinei linijai siūloma keletas kalibravimo būdų, įrenginys bandiniui prispausti prie linijos. Bešvinė NBT-LMT keramika buvo tyrinėjama dielektrinės spektroskopijos metodais. Gauti rezultatai rodo, kad NBT-LMT keramikų grupėje elektriniam laidumui galioja Maerio-Neldelio taisyklė. / Šiame darbe nagrinėjamos galimybės patobulinti plačiajuostės dielektrinės spektroskopijos metodus naudojant skaitmeninius ir analitinius daugelio modų dielektrinės skvarbos skaičiavimo metodus, tiriami (1-x)(Na1/2 Bi1/2)TiO3 - xLa(Mg1/2 Ti1/2)O3 (NBT-LMT) keramikų grupės laidumo ypatumai. Nagrinėjama galimybė pritaikyti HFSS skaitmeninio modeliavimo programą dielektrinės spektroskopijos tikslams. Naudojant šią programinę įrangą, apskaičiuojama dielektrinė ir magnetinė skvarbos komplikuotiems mikrojuostelinės linijos ir dalinai užpildyto bangolaidžio matavimo grandinių atvejams. Pateikiami patobulinti kondensatoriaus koaksialinėje linijoje ir ribotų matmenų atviro galo koaksialinės linijos matematiniai modeliai. Šie modeliai patikrinami skaitmeniniu metodu. Naudojant daugiamodį kondensatoriaus modelį, atsižvelgus į magnetinio lauko pasiskirstymą koaksialinėje matavimo grandinėje, pasiūlomas būdas pamatuoti mažai bandinio magnetinei skvarbai, kai dielektrinė skvarba didelė (dešimtim ar šimtais kartų didesnė už magnetinę skvarbą). Atviro galo koaksialinei linijai siūloma keletas kalibravimo būdų, įrenginys bandiniui prispausti prie linijos. Bešvinė NBT-LMT keramika buvo tyrinėjama dielektrinės spektroskopijos metodais. Gauti rezultatai rodo, kad NBT-LMT keramikų grupėje elektriniam laidumui galioja Maerio-Neldelio taisyklė.

Recent research focuses on expanding the use of RF/Microwave circuits and systems to include multi-disciplinary applications. One example is the detection of the dielectric properties of chemicals and bio-chemicals at microwave frequencies, which is useful for pharmaceutical applications, food and drug safety, medical diagnosis and material characterization. Dielectric spectroscopy is also quite relevant to detect the frequency dispersive characteristics of materials over a wide frequency range for more accurate detection. In this dissertation, on-chip and on-board solutions for microwave chemical sensing are proposed. An example of an on-chip dielectric detection technique for chemical sensing is presented. An on-chip sensing capacitor, whose capacitance changes when exposed to material under test (MUT), is a part of an LC voltage-controlled oscillator (VCO). The VCO is embedded inside a frequency synthesizer to convert the change in the free runing frequency frequency of the VCO into a change of its input voltage. The system is implemented using 90 nm CMOS technology and the permittivities of MUTs are evaluated using a unique detection procedure in the 7-9 GHz frequency range with an accuracy of 3.7% in an area of 2.5 × 2.5 mm^2 with a power consumption of 16.5 mW. The system is also used for binary mixture detection with a fractional volume accuracy of 1-2%. An on-board miniaturized dielectric spectroscopy system for permittivity detec- tion is also presented. The sensor is based on the detection of the phase difference be- tween the input and output signals of cascaded broadband True-Time-Delay (TTD) cells. The sensing capacitor exposed to MUTs is a part of the TTD cell. The change of the permittivity results in a change of the phase of the microwave signal passing through the TTD cell. The system is fabricated on Rogers Duroid substrates with a total area of 8 × 7.2 cm2. The permittivities of MUTs are detected in the 1-8 GHz frequency range with a detection accuracy of 2%. Also, the sensor is used to extract the fractional volumes of mixtures with accuracy down to 1%. Additionally, multi-band and multi-standard communication systems motivate the trend to develop broadband front-ends covering all the standards for low cost and reduced chip area. Broadband amplifiers are key building blocks in wideband front-ends. A broadband resistive feedback low-noise amplifier (LNA) is presented using a composite cross-coupled CMOS pair for a higher gain and reduced noise figure. The LNA is implemented using 90 nm CMOS technology consuming 18 mW in an area of 0.06 mm2. The LNA shows a gain of 21 dB in the 2-2300 MHz frequency range, a minimum noise figure of 1.4 dB with an IIP3 of -1.5 dBm. Also, a four-stage distributed amplifier is presented providing bandwidth extension with 1-dB flat gain response up to 16 GHz. The flat extended bandwidth is provided using coupled inductors in the gate line with series peaking inductors in the cascode gain stages. The amplifier is fabricated using 180 nm CMOS technology in an area of 1.19 mm2 achieving a power gain of 10 dB, return losses better than 16 dB, noise figure of 3.6-4.9 dB and IIP3 of 0 dBm with 21 mW power consumption. All the implemented circuits and systems in this dissertation are validated, demonstrated and published in several IEEE Journals and Conferences.

In this work the electrical insulating properties of the nanocomposite materials based on poly(ethylene-co-butyl acrylate) filled with alumina nanoparticles are studied. The dielectric properties chosen for the evaluation are the dielectric permittivity and loss as well as the breakdown strength and the pre-breakdown currents. The reason for choosing these particular properties is partly due to the importance of these for the general electrical applications and partly due to the uncertainties involved for these particular properties of the nanocomposite materials. The importance of moisture absorption for the dielectric properties is outlined in this work. All measurements were performed in both dry conditions and after conditioning of the materials in humid environment until saturation. The data for moisture absorption was taken from the water absorption study performed at the Department of Fibre and Polymer Technology, KTH. The dielectric spectroscopy in frequency domain was employed for measuring dielectric permittivity and loss. Havriliak-Negami approximation was used for characterization of the measurement data and at the same time ensuring the fulfillment of the Kramers-Kronig relations. Results from the dielectric spectroscopy study in dry conditions suggest that dielectric spectroscopy can be used for evaluating nanoparticle dispersion in the host matrix, based on correlation between the morphology data obtained from SEM investigation and the scatter in the dielectric loss. The dielectric spectroscopy study performed on the nanocomposites after conditioning in humid environment showed that absorbed moisture has a distinct impact on the dielectric loss. Especially pronounced is its’ influence on the frequency behavior, when the dielectric loss peaks are shifted towards higher frequencies with increased moisture content. The nanocomposite materials characterized by higher specific surface area generally exhibit higher dielectric losses. Surface functionalization of the nanoparticles does not seem to have much influence on the dielectric loss in dry conditions. After conditioning in humid environment, however, the surface modification was shown to have a significant impact. Temperature is another significant factor for the frequency behavior of the dielectric loss: it was found that the studied nanocomposites can be characterized by Arrhenius activation. The breakdown strength and pre-breakdown currents study outlined the influence of moisture as well. The study indicated that surface treatment of the nanoparticles can enhance properties of the nanocomposite materials, namely aminopropyltriethoxy silane was an especially successful choice: • The highest breakdown strength was determined by the study for NDA6 material formulation in dry conditions. • After conditioning in humid environment the NDA6 material continued showing the best breakdown strength among the nanocomposite mate rials, as well as this value was close to the breakdown strength of the reference unfilled material. This study confirms the existence of the optimal nanofiller content or rather optimal specific surface area of the dispersed nanoparticles in the host matrix. The latter is supported by the comparison between the nanocomposites based on nanoparticles with two different specific surface areas, which shows that the dielectric properties worsen, i.e. the dielectric losses increase and the influence of absorbed moisture on the breakdown strength becomes more pronounced, for nanomaterials with larger specific surface area. The pre-breakdown currents were found to follow space-charge limited conduction mechanism reasonably well. The following conduction regimes were identified: constant region (likely due to measurement difficulties at low field strengths), Ohm’s regime, trap-filled-limit regime and trapfree dielectric regime. The breakdown usually occurred either during the trap-filled-limit regime, when the current increased dramatically for the small change in electric field, or during the trapfree dielectric regime. The threshold values between different conduction regimes seem to correlate well with the oxidation induction times (OIT), which in turn depend on the total specific surface area. The pre-breakdown currents tend to be highest for the materials filled with the untreated nanoparticles. Increased absorbed moisture content causes higher pre-breakdown currents for the nanocomposite materials, while for the reference unfilled material the pre-breakdown currents do not show such tendency. Generally it can be said that the repeatability in the measured data is higher for the nanocomposite materials in comparison to the unfilled host material, as was demonstrated by both dielectric spectroscopy and breakdown studies. / <p>QC 20130207</p>

Šiame darbe nagrinėjamos galimybės patobulinti plačiajuostės dielektrinės spektroskopijos metodus naudojant skaitmeninius ir analitinius daugelio modų dielektrinės skvarbos skaičiavimo metodus, tiriami (1-x)(Na1/2 Bi1/2)TiO3 - xLa(Mg1/2 Ti1/2)O3 (NBT-LMT) keramikų grupės laidumo ypatumai. Nagrinėjama galimybė pritaikyti HFSS skaitmeninio modeliavimo programą dielektrinės spektroskopijos tikslams. Naudojant šią programinę įrangą, apskaičiuojama dielektrinė ir magnetinė skvarbos komplikuotiems mikrojuostelinės linijos ir dalinai užpildyto bangolaidžio matavimo grandinių atvejams. Pateikiami patobulinti kondensatoriaus koaksialinėje linijoje ir ribotų matmenų atviro galo koaksialinės linijos matematiniai modeliai. Šie modeliai patikrinami skaitmeniniu metodu. Naudojant daugiamodį kondensatoriaus modelį, atsižvelgus į magnetinio lauko pasiskirstymą koaksialinėje matavimo grandinėje, pasiūlomas būdas pamatuoti mažai bandinio magnetinei skvarbai, kai dielektrinė skvarba didelė (dešimtim ar šimtais kartų didesnė už magnetinę skvarbą). Atviro galo koaksialinei linijai siūloma keletas kalibravimo būdų, įrenginys bandiniui prispausti prie linijos. Bešvinė NBT-LMT keramika buvo tyrinėjama dielektrinės spektroskopijos metodais. Gauti rezultatai rodo, kad NBT-LMT keramikų grupėje elektriniam laidumui galioja Maerio-Neldelio taisyklė. / One of the basic problems in measurements of the electrical properties of materials is finding relations between measured electrical values and characteristics of the material, especially when the field distribution in the device under test with a sample inside is complex. Commercial electromagnetic simulation software was used in unconventional way to calculate materials' electrical properties. Because the software is not adopted for this task, built-in optimisation option was used. In this way dielectric and magnetic properties of materials in very complex shape were calculated. The method was tested by calculation of complex dielectric permittivity of Bi1.5ZnNb1.5O7-xF2 pyrochlore ceramics as well as by calculation of both complex dielectric permittivity and complex dielectric permeability of carbon-coated capsules of Ni embedded into polyurethane matrix from experimental results. Due to the fact that using numerical methods is time consuming, a mathematical model on mode matching approach of rectangular rod in a waveguide and a new model of multimode capacitor were developed. Models were checked by numerical methods. On a high frequency, when electric field in the sample is inhomogeneous, the magnetic field in the sample is much stronger than in the transmission line. Thus, the magnetic permeability of the sample will affect scattering parameters. Based on this circumstance, the method to measure small magnetic permeability using capacitor like in coaxial line when... [to full text]

Mit dieser Arbeit ist weltweit zum ersten Mal die molekulare Dynamik von vereinzelten,d.h. einander nicht berührenden Polymerketten experimentell bestimmt worden. Die Grundlagen dafür sind einerseits die breitbandige dielektrische Spektroskopie mit ihrer außerordentlich hohen experimentellen Empfindlichkeit und andererseits die Weiterentwicklung einer speziellen Probenanordnung, bei der hochleitfähige Silizium-Elektroden durch elektrisch isolierende Siliziumdioxid-Nanostrukturen in einem vordefinierten Abstand gehalten werden und so den Probenkondensator bilden. Im Rahmen dieser Arbeit wurde die Höhe der Nanostrukturen (und damit des Elektrodenabstands) auf nur 35 nm reduziert. Damit gelang der Nachweis, dass selbst vereinzelte kondensierte Polymer-Knäuel - im Rahmen der Messgenauigkeit - dieselbe Segmentdynamik (bzw. denselben dynamischen Glasübergang), gemessen in ihrer mittleren Relaxationsrate, wie die makroskopische Schmelze („bulk“) aufweisen. Nur ein kleiner Anteil der Segmente zeigt eine langsamere Dynamik, was auf attraktive Wechselwirkungen mit dem Substrat zurückzuführen ist, wie komplementäre Untersuchungen mittels Infrarot-Spektroskopie zeigen. Zudem bieten diese Experimente die Möglichkeit, nach der dielektrischen Messung die mit Nanostrukturen versehene obere Elektrode zu entfernen und die Verteilung der vereinzelten Polymerketten, deren Oberflächenprofile und Volumen mit dem Rasterkraftmikroskop zu bestimmen. Erst damit gelingt der Nachweis, dass die Polymer-Knäuel im Mittel aus einer einzelnen Kette bestehen. Die Kombination dieser drei unabhängigen Messmethoden liefert ein schlüssiges und detailliertes Bild, gekennzeichnet dadurch, dass attraktive Oberflächenwechselwirkungen die Glasdynamik nur über ca. 0,5nm direkt beeinflussen. In einem zweiten Teil trägt die Arbeit mit der Untersuchung dünner Polymerschichten im Nanometer-Bereich zu einer international geführten, kontroversen Diskussion um die Frage, ob sich im Falle solcher räumlichen Begrenzungen der dynamische und kalorimetrische Glasübergang ändern, bei. Dabei zeigt mit den präsentierten dielektrischen und ellipsometrischen Messungen eine Kombination aus einer Methode, die im Gleichgewichtszustand misst und einer, die den Übergang in den Nichtgleichgewichtszustand bestimmt, dass sich sowohl Polystyrol-Schichten verschiedener Molekulargewichte bis zu einer Dicke von nur 5 nm als auch Polymethylmethacrylat-Schichten auf unterschiedlichen (hydrophilen und hydrophoben) Substraten bis zu einer Dicke von 10 nm weder in ihrem dynamischen noch ihrem kalorimetrischen Glasübergang von der makroskopischen Schmelze unterscheiden.

Les dispersions colloïdales de nanoparticules (NPs) sont très répandues dans l'industrie, et permettent d'éviter l'utilisation de NPs sèches, controversée pour des raisons de toxicité. Le contrôle des interactions entre les NPs et le milieu dispersant reste le point clé de ces systèmes. La modulation de ces interactions permet de contrôler l'état de dispersion des NPs dans les sols. De plus, les nanocomposites NPs-polymère se sont avérés prometteurs pour une large gamme d'applications, ainsi l'utilisation de sols pourrait présenter une voie avantageuse d'incorporation des NPs dans le polymère, tout en offrant la possibilité de contrôler leur état de dispersion, et in fine les propriétés du matériau, celles-ci étant liées à l'état de dispersion des NPs. L'objectif de ce travail de thèse est le développement de méthodes de modification de surface de NPs d'oxyde en dispersion colloïdale, tout en contrôlant la dispersion des NPs dans les sols et dans les nanocomposites issus de ces sols. Puis, l'évaluation de cet état de dispersion par SAXS. Deux méthodes de modification de surface ont ainsi été développées : la première implique le greffage d'acides phosphoniques sur des NPs de silice recouvertes d'alumine en dispersion dans l'eau, et la seconde met en jeu le greffage d'acides phosphoniques sur des NPs de TiO2 et leur transfert d'une phase aqueuse à une phase CHCl3. Les NPs modifiées ont été caractérisées par diverses méthodes. Leur état de dispersion a été étudié par DLS et SAS. De plus, pour les NPs de silice-amine, l'impact de la densité de greffage du C8PA sur la structure des NPs (à l'état sec) a été mis en évidence par SAXS et différents processus de relaxation ont été étudiés par BDS pour les NPs nues et modifiées. Enfin, ces NPs ont été incorporées dans un polymère de PEA par voie aqueuse via des latex et leur état de dispersion dans les composites a été mesuré par SANS. / Colloidal nanoparticles (NPs) dispersions are largely used in the industry, and avoid the use of dried NPs, which is controversial due to safety concerns. The key point in such systems remains the control of the interactions with the dispersed medium and between the NPs. Mastering these interactions allows controlling the NPs' state of dispersion. Moreover, as polymer-NPs nanocomposites have been found promising for a wide variety of applications, the use of colloidal sols could thus be an advantageous way of NPs' incorporation in the polymer, with a possible control of the NPs state of dispersion, and finally on the properties of the material, as they are linked to the NPs' dispersion. The purpose of this PhD work is to develop surface-functionalization methods of oxide NPs in colloidal sols in order to control the dispersion of NPs in the sols and in polymer nanocomposites derived from these sols, and to evaluate this dispersion using SAXS. Two surface modification methods have been developed to obtain aqueous or organic sols of functionalized NPs. The first one concerns the reaction in water of alumina-coated silica NPs with phosphonic acids (PAs), and the second one involves the simultaneous grafting and phase transfer of TiO2 NPs from an aqueous to a CHCl3 phase using PAs. The resulting NPs were characterized and their state of dispersion was monitored by DLS and SAS measurements. The impact of the C8PA grafting density on the structure of modified alumina-coated silica NPs in the dried state was evidenced by SAXS. The different relaxation processes of bare and grafted NPs were studied by BDS. These NPs were then incorporated in a PEA polymer by an aqueous latex route, and their structure in the nanocomposites was investigated by SANS.

[EN] The development of new and more complex polymeric materials involves challenging problems to basic sciences. The relationship between structure and molecular dynamics assumes great importance for the future development of novel technologies based on such polymers. Thus, the understanding of how small changes in the chemical structure affect the properties of the material is essential to progress in the technological and scientific area. An in-depth analysis of the molecular mobility leads to establish the structure-properties relationships. On this basis, the main aim of the present work is to study the molecular mobility of two different families of polymeric materials. For this purpose, the experimental techniques mainly used were Differential Scanning Calorimetry (DSC) and Dielectric Relaxation Spectroscopy (DRS). The first family of polymers characterized was a series of chemically cross-linked copolymers composed by Vinylpyrrolidone (VP) and Butyl Acrylate (BA) monomers. In the first place, the influence of the monomer molar ratio (XVP/YBA) on the copolymer properties was studied. Thus, a Fourier Transform Infrared Spectroscopy (FTIR) analysis verified dipole-dipole interactions between amide groups. The influence of these interactions on several parameters related to the molecular mobility was evidenced by the DSC, DRS and Dynamic Mechanical Analysis (DMA) techniques. Secondly, the effect of the cross-link density on the molecular dynamics of 60VP/40BA copolymers was analyzed using DSC and DRS. One single glass transition was detected by DSC measurements. The DRS analysis showed that an increase of the cross-linking produced a typical effect on the alpha process dynamics. However, the beta process, which possessed typical features of pure JG relaxation, unexpectedly lost the intermolecular character for the highest cross-linker content. The fastest gamma process was relatively unaffected. The second family of polymeric materials studied was a series of segmented polycarbonatediol polyurethane (PUPH) modified with different amounts of expanded graphite (EG) conductive filler. Scanning Electron Microscopy (SEM), X-ray diffraction measurements and FTIR analysis demonstrated a homogeneous dispersion of the EG filler in the matrix. DRS was used to study the dielectric properties of the PUPH/EG composites. The dielectric permittivity of the composites showed an insulator to conductor percolation transition with the increase of the EG content (20&#61485;30 wt%). The addition of expanded graphite to the matrix caused a dramatic increase in the electrical conductivity of ten orders of magnitude, which is an indication of percolative behavior. / [ES] El desarrollo de nuevos materiales poliméricos de mayor complejidad produce un desafío cada vez mayor en el área de las ciencias básicas. La relación entre la estructura y la dinámica molecular resulta de gran importancia para el desarrollo de nuevas tecnologías basadas en estos materiales poliméricos. Así, una mayor comprensión de cómo pequeños cambios en la estructura química afectan a las propiedades de los materiales resulta esencial para el progreso científico y tecnológico. Un análisis en profundidad de la movilidad molecular permite establecer las relaciones estructura-propiedades. Partiendo de esta base, el principal objetivo del presente trabajo es el estudio de la movilidad molecular de dos familias diferentes de materiales poliméricos. Para ello, las técnicas experimentales utilizadas fueron principalmente la Calorimetría Diferencial de Barrido (DSC) y la Espectroscopia de Relajación Dieléctrica (DRS). La primera familia de polímeros caracterizada fue una serie de copolímeros entrecruzados químicamente compuestos por los monómeros Vinilpirrolidona (VP) y Acrilato de Butilo (BA). En primer lugar, se estudió la influencia de la proporción molar de monómero (XVP/YBA) en las propiedades del copolímero. A través de un análisis por Espectroscopia de Infrarrojo por Transformada de Fourier (FTIR), se verificó la existencia de interacciones dipolo-dipolo entre los grupos amida. Mediante el análisis por DSC, DRS y Análisis Dinamomecánico (DMA), se evidenció la influencia de estas interacciones en diferentes parámetros relacionados con la movilidad molecular. En segundo lugar, se analizó el efecto de la densidad de entrecruzamiento en la dinámica molecular de los copolímeros 60VP/40BA usando DSC y DRS. A través de las medidas de DSC se observó una única transición vítrea para todos los entrecruzamientos. El análisis por DRS mostró como el incremento en entrecruzante produjo el típico efecto en la dinámica del proceso alpha, pero sin embargo, el proceso beta, que tenía las características típicas de una relajación JG, perdió de forma inesperada su carácter intermolecular para el mayor contenido en entrecruzante. El proceso gamma no se vio afectado. La segunda familia de materiales poliméricos estudiada fue una serie de poliuretanos segmentados (PUPH) modificados con diferentes cantidades de grafito expandido (EG), utilizado como relleno conductivo (desde 0 a 50% en peso). El análisis de los resultados obtenidos mediante Microscopía Electrónica de Barrido (SEM), Difracción de Rayos X y FTIR demostró la homogénea dispersión del relleno de EG en la matriz de PUPH. La técnica DRS se usó para estudiar las propiedades dieléctricas de los materiales compuestos PUPH/EG. La permitividad dieléctrica de los materiales mostró una transición de percolación desde aislante a conductor al incrementarse el contenido en EG (rango de 20-30% en peso). La adición de grafito expandido a la matriz de PUPH causó un incremento significativo en la conductividad dieléctrica de diez órdenes de magnitud, lo que indica el comportamiento de percolación. / [CAT] El desenvolupament de nous materials polimèrics de major complexitat produeix un desafiament cada vegada major en l'àrea de les ciències bàsiques. La relació entre l'estructura i la dinàmica molecular resulta de gran importància per al desenrotllament de noves tecnologies basades en aquests materials polimèrics. Així, una major comprensió de com petits canvis en l'estructura química afecten a les propietats dels materials, resulta essencial per al progrés científic i tecnològic. Un anàlisis en profunditat de la mobilitat molecular permet establir les relacions estructura-propietats. Partint d'aquesta base, el principal objectiu del present treball és l'estudi de la mobilitat molecular de dues famílies diferents de materials polimèrics. Per a això, les tècniques experimentals utilitzades van ser principalment la Calorimetria Diferencial de Rastreig (DSC) i l'Espectroscòpia de Relaxació Dielèctrica (DRS). La primera família de polímers caracteritzada va ser una sèrie de copolímers entrecreuats químicament compostos pels monòmers Vinilpirrolidona (VP) i Acrilat de Butilo (BA) . En primer lloc, es va estudiar la influència de la proporció molar de monòmer (XVP/YBA) en les propietats del copolímer. A través d'una anàlisi per Espectroscòpia d'Infraroig per Transformada de Fourier (FTIR), es va verificar l'existència d'interaccions dipol-dipol entre els grups amida. Mitjançant l'anàlisi per DSC, DRS i Anàlisi Dinamomecánico (DMA), es va evidenciar la influència d'aquestes interaccions en diferents paràmetres relacionats amb la mobilitat molecular. En segon lloc, es va analitzar l'efecte de la densitat d'entrecreuament en la dinàmica molecular dels copolímers 60VP/40BA mitjançant DSC i DRS. A través de les mesures de DSC es va observar una única transició vítria per a tots els continguts d'agent entrecreuant . L'anàlisi per DRS va mostrar com l'increment en agent entrecreuant va produir l'efecte esperat en la dinàmica del procés alfa. En canvi, el procés beta, que tenia les característiques típiques d'una relaxació JG, va perdre de forma inesperada el seu caràcter intermolecular per al major contingut en agent entrecreuant. El procés més ràpid gamma no es va veure afectat. La segona família de materials polimèrics estudiada va ser una sèrie de poliuretans segmentats (PUPH) modificats amb diferents quantitats de grafit expandit (EG) , utilitzat com a farcit conductiu (des de 0 a 50% en pes). L'anàlisi dels resultats obtinguts per mitjà de Microscòpia Electrònica de Rastreig (SEM), Difracció de Rajos X i FTIR va mostrar la dispersió homogènia del EG en la matriu de PUPH. La tècnica DRS es va utilitzar per a estudiar les propietats dielèctriques dels materials compostos PUPH/EG. La permitivitat dielèctrica dels materials va mostrar una transició de percolació des d'aïllant a conductor amb l'increment de contingut en EG (20-30% en pes). L'addició d'EG a la matriu de PUPH va causar un increment significatiu en la conductivitat dielèctrica, de deu ordes de magnitud. / Redondo Foj, MB. (2015). A contribution to the study of the molecular mobility in polymeric materials by Thermal and Dielectric Analysis [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/59457 / TESIS

<div> Design rules and application spaces for closed-shell conjugated polymers have been well established in the field of organic electronics, and this has allowed for significant breakthroughs to occur in myriad device platforms [e.g., organic field-effect transistors (OFETs) and organic light-emitting devices (OLEDs)]. Conversely, organic electronic materials that are based on the emerging design motif that includes open-shell stable radicals have not been evaluated in such detail, despite the promise these materials show for charge transfer, light-emission, and spin manipulation platforms. Moreover, recent results have demonstrated that the materials performance of hybrid systems will allow for future applications to harness both of these platform design archetypes to generate composites that combine the performance of current state-of-the-art conjugated polymer systems with the novel functions provided by open-shell species. Thus, establishing the underlying physical phenomena associated with the interactions between both classes of materials is imperative for the effective utilization of these soft materials.</div><div><br></div><div> In the first part of this work, Förster resonance energy transfer (FRET) is demonstrated to be the dominant mechanism by which energy transfer occurs from a common conjugated polymer to various radical species using a combination of experimental and computational approaches. Specifically, this is determined by monitoring the fluorescence quenching of poly(3hexylthiophene) (P3HT) in the presence of three radical species: (1) the galvinoxyl; (2) the 2phenyl-4,4,5,5-tetramethylimidazoline-3-oxide-1-oxyl (PTIO); and (3) the 4-hydroxy-2,2,6,6tetramethylpiperidine-1-oxyl (TEMPO) radicals. Both in solution and in the solid-state, the galvinoxyl and PTIO radicals show quenching on par with that of a common fullerene electronaccepting derivative. Conversely, the TEMPO radical shows minimal quenching at similar concentrations. Using both ultrafast transient absorption spectroscopy and computational studies, FRET is shown to occur at a significantly faster rate than other competing processes. These findings suggest that long-range energy transfer can be accomplished in applications when radicals that can act as FRET acceptors are utilized, forming a new design paradigm for future applications involving both closed- and open-shell soft materials.</div><div><br></div><div> Following this, addition of the galvinoxyl radical to P3HT is shown to alter the thin film transistor response from semiconducting to conducting. This is accompanied by a modest enhancement in electrical conductivity. This interaction is not seen with either the TEMPO or PTIO radicals. While an increase in charge carrier concentration is observed, the interaction is not otherwise consistent with a simple charge-transfer doping mechanism, due to the mismatched reduction and oxidation potentials of the two species. Additionally, no freeze-out of charge carriers is observed at reduced temperatures. It is also not due to parallel conduction through the radical fraction of the bulk composite, as the radical species is non-conductive. Hole mobility is enhanced at lower concentrations of the radical, but it decreases at higher concentrations due to the reduced fraction of conductive material in the polymer bulk. Despite the increase in mobility at lower concentrations, the activation energy for charge transport is increased by the presence of the radical. This suggests that the radical is not improving the charge transport through filling of deep trap states or by reducing the activation energy for the charge transport reaction; however, the galvinoxyl radical is likely filling shallow trap states within the P3HT for the composite thin film.</div><div><br></div><div> Finally, a novel analysis technique for polymer relaxation is investigated through dielectric spectroscopy of model polyalcohols. An understanding of relaxation phenomena and the physics of amorphous solids in general remains one of the grand open challenges in the field of condensed matter physics. This problem is particularly relevant to organic electronics as many organic electronic materials are found in the amorphous state, and their physical relaxation can lead to undesirable effects such as hysteresis and instability. Current procedures describe relaxation phenomena in terms of empirical functions, but the physical insights provided by this representation are limited. The new approach instead represents the dielectric response as a spectrum of Debye processes. Rather than varying the spectral strength at fixed time points as traditional spectral analysis implicitly does, this approach instead varies the characteristic time of each spectral element while the strength remains fixed. This allows the temperature dependence on relaxation time of each spectral element to be determined, and the <i>α</i>- and <i>β</i>-relaxation are interpreted in light of this analysis. </div><div> </div>