In der heutigen Zeit sind optoelektronische Bauelemente allgegenwärtig. Sie finden Anwendung für Beleuchtungszwecke, in Anzeigen und für die Telekommunikation. Die Entwicklung dieser Anwendungen wurde lange Zeit von anorganischen Halbleitern getragen, in jüngerer Vergangenheit auch von der organischen Elektronik. Neuerdings werden verstärkt Konzepte entwickelt, um die spezifischen Vorteile der jeweiligen komplementären Materialklassen auszunutzen. Für diese Hybridisierung müssen die Eigenschaften der verschiedenen Materialien, insbesondere die elektronische Struktur, genau auf einander abgestimmt sein. In dieser Arbeit werden Leiter-para-phenylene auf spektrale Überlagerung und angepasste Orbitalenergien mit ZnO, auf chemische Inertheit und auf die Bildung von dünnen Schichten über vakuumbasierte Verarbeitungsmethoden optimiert. Dazu konzentriert sich der synthetische Gesichtspunkt auf die selektive Funktionalisierung der verschiedenen Methylenbrücken mit Alkyl-, Aryl- und Fluorsubstituenten. Die finalen Stufen werden bezüglich ihrer optischen Eigenschaften mittels Absorption und Fluoreszenz, bezüglich ihrer elektrochemischen Eigenschaften und bezüglich ihrer Festkörperstruktur mittels Röntgenstrukturanalyse von Einkristallen charakterisiert. Außerdem widmet sich ein erheblicher Teil dieser Arbeit der Erforschung des photochemischen Abbaus von fluorenbasierten Strukturen. Es werden neue Erkenntnisse zum Abbaumechanismus und der Ursache der grünen Emission gewonnen. Weiterhin werden die Abbauraten von Fluorenstrukturen mit verschiedenen Brückensubstituenten verglichen. Dabei konnten auch verschiedene Reaktionsprodukte und Mechanismen nachgewiesen werden. Letztendlich wird auch die Anwendung einzelner Derivate in Hybridstrukturen diskutiert. / Nowadays optoelectronic devices are ubiquitous for illumination purposes, in telecommunication and displays. For a long time, the development for these devices was driven by inorganic semiconductors, later organic semiconductors contributed, as well. Recently concepts have been developed to combine both complementary material classes to exploit the specific advantages of each one. For the hybridization, the properties of the materials, especially the electronic structure, have to match very well. In this work the optimization of ladder-type p-phenylenes towards spectral overlap and energy level alignment with ZnO, vacuum-processability, inertness, as well as layer formation is described. In terms of molecular design the different properties are addressed by site-selective functionalization of the methylene bridges with alkyl, aryl, and fluoro groups. The final products are characterized regarding their optical properties by absorption and fluorescence, their electrochemical properties, as well as their solid-state structure by single crystal X-ray diffraction. Apart from that, a large part of the work is devoted to investigations of the photochemical degradation of fluorene-type structures. New insights are gained into the mechanism of degradation, as well as the origin of the green emission in ladder-type structures The dependence of the rate of degradation is described semi-quantitatively with respect to the substitution pattern. By that, different reaction mechanisms for different substituents are found. Finally, the integration of some products in hybrid structures is discussed.

This thesis is concerned with the photophysical and nonlinear optical responses, and applications of a set of conjugated polymers and small molecules in the visible and near-IR spectral regions. Poly(phenylene ethynylene) PPE polymers were substituted with conjugated side-arms in a cruciform fashion to determine the impacts of electronic coupling on the one-photon (1PA), two-photon (2PA), and excited state absorption (ESA) properties of the co-polymer system. The cruciform-like PPEs showed significant changes in their nonlinear and phophysical behavior relative to their linear models, including shifts and splittings of the 1PA bands due to moderate mixing of the lowest singlet excited states, an increase in the 2PA cross section (δ) values, and an increase in the yield of triplet excited-state species. The cruciform-like PPE polymers exhibited effective optical pulse suppression of femtosecond and nanosecond laser pulses over a broad spectral range of ~200 nm in the visible and near-IR. The suppression capability of the cruciform-like PPEs exceeded the best reported value for alkyl-substituted PPE polymers. The spectroscopic effects due to conjugation length, structural configuration, and intramolecular charge transfer (ICT) are discussed for a family of bent donor-acceptor-donor (D-A-D) -type conjugated oligomers, which incorporate electron-rich triarylamine donors and electron-deficient triarylborane acceptor units into its conjugated structure. These organoborane oligomers are highly fluorescent and exhibit strong 2PA in the visible region with δ values as large as 1410 GM, as well as overlapping ESA bands attributed to singlet-singlet and triplet-triplet absorption. Saturation of the molar absorptivity, ε, and δ was observed at less than two repeat monomer units due to conformational disorder in the oligomer with increasing length. Positive solvatochromism of fluorescence with solvent shifts as large as ~70 nm was observed as a result of ICT from the arylamine donors to boryl-centered acceptor sites. The excited-state dynamics also show sensitivity to the solvent environment. Experimental findings suggest that these organoborane oligomers may have potential use as nonlinear material for optical power limiting (OPL) and two-photon sensing applications. The spectral properties of two bis-donor chromophores, (bis(diarylamino)biphenyl (TPD) and distyrylthiophene (DST), were investigated with and without the presence of AgNPs in order to better understand the local-field enhancement and subsequent effects on the photophysics and nonlinear behavior of 2PA dyes. While little changes were observed in the excited-state dynamics, measurements of nanoparticle aggregate-dye composite solutions with TPD revealed a 1.6-enhancement in the two-photon excited fluorescence signal. OPL measurements of nanosecond laser pulses at 532 nm revealed a reduction in threshold energy by a factor of 2 in solutions containing TPD and AgNP aggregates, relative to solutions of TPD alone. DST shows exceptional solubility (>1 M) in several organic solvents and exhibits a 2PA spectrum that overlaps well with its singlet-singlet and triplet-triplet ESA bands. Consequently, DST exhibits effective optical limiting of nanosecond laser pulses through two-photon induced excited-state absorption over a broad spectral range of approximately 200 nm in the red and near-IR.

Esta tese de doutorado apresenta os resultados do estudo sistemático das propriedades ópticas das interfaces que aparecem em dispositivos orgânicos atuais emissores de luz ou OLEDs. Estamos interessados no entendimento do papel de cada uma das interfaces metal/polímero e ITO/polímero sobre a emissão da camada orgânica ativa emissora de luz. Para tanto, se fez necessário o domínio de todas as etapas de preparação e caracterização de filmes finos orgânicos, desde a síntese química dos polímeros até a preparação de amostras adequadas que permitissem a realização dos objetivos propostos. Ênfase foi dada aos processos de excitação e de relaxação energética dos portadores de carga (elétrons e buracos) em filmes ultrafinos automontados próximos às interfaces, correlacionando-os direta ou indiretamente com os efeitos de interface. Através do desenvolvimento e domínio de uma nova metodologia de preparação de filmes orgânicos, verificamos que a intensidade da luminescência de um filme de prova ultrafino de poli(p-fenileno vinileno) (PPV) com espessura em torno de 1,5 nm sofre grandes variações em uma extensa região próxima às interfaces metálicas de Au, Al e de ITO (óxido de índio-estanho). Esta camada de prova foi gradualmente separada da interface variando-se de forma controlada a espessura de um filme polimérico espaçador opticamente inerte. O perfil de intensidade da fotoluminescência nas proximidades das interfaces foi determinado em função da distância entre as superfícies estudadas (vidro, quartzo, metálica ou ITO) e a camada de prova emissora de PPV. Duas regiões relacionadas a processos radiativos distintos foram bem estabelecidas para as interfaces metálicas: uma região de extinção, nas proximidades da interface (< 20 nm), onde a luminescência é fortemente suprimida e uma outra de aumento da luminescência entre 20 e 90 nm. A grande variação da intensidade da luminescência observada neste trabalho é explicada considerando efeitos de interferência em uma semicavidade óptica, além dos processos de transferência de energia tipo Förster entre estados do PPV e estados de plásmons superficiais no metal. Verificamos que a distribuição espacial da radiação emitida é profundamente alterada por processos não radiativos de transferência de energia e pelas condições impostas pelas interfaces em uma semicavidade óptica. Modificações da superfície de ITO foram realizadas pelo tratamento acídico com água-régia suave. Nós observamos que a refletividade do ITO é fortemente dependente do tempo do tratamento e da espessura do espaçador. Como nos filmes metálicos, a emissão de um filme de prova de PPV sofre alterações nas proximidades da interface contendo ITO. Aqui, os parâmetros materiais (índice de difração, reflectância e comprimento de onda da emissão), a estrutura de superfície do ITO e os fatores geométricos mostram um papel importante. Cálculos da intensidade da emissão nas proximidades das interfaces descrevem de modo satisfatório os resultados experimentais. Do perfil de intensidade calculado próximo das interfaces, concluímos que a espessura e a posição da camada ativa emissora de luz devem ser otimizadas de modo a coincidir com a região de aumento ou amplificação da luminescência. / This PhD thesis is an extensive study of the optical properties of the interfaces of organic light-emitting devices (OLED’s). In particular, we investigated the influence of interfaces metal/polymer and ITO/polymer on the emission of an active layer in such devices. Therefore, it was necessary to dominate all the processes of fabrication and characterization of the multilayered structures used in the present investigation. We have used a very thin PPV probe layer (1.5 nm) to map the optical properties very near the metal/organic and the Indium-Tin Oxide (ITO)/organic interfaces. A new Spin-Layer-by-Layer method was employed which allowed a control of deposition of layers at the monolayer level. Precise variation of the metal/PPV or ITO/PPV separation over the entire substrate surface was achieved by the deposition of an organic inert spacer layer. The ITO surface modifications were carried out by soft acidic aquaregia treatment. A strong modulation of the probe layer emission was observed near the metal and ITO interfaces. These results are explained by calculations which include competing short range radiationless energy transfer and intensity modulation due effects produced by the optical cavity formed by metal/polymer films/air. At small distances (<20 nm) from interface, collective excitations in the metal act as energy acceptors, which open up an efficient nonradiative channel. Here, material parameters (diffraction index, reflectance and emission wavelength, for example), surface treatment and structure as well as geometrical factors may play an important role.

No description available.

Nanophase-separated hydrophilic-hydrophobic multiblock copolymers are promising proton exchange membrane (PEM) materials due to their ability to form various morphological structures which enhance transport. Four arylene chlorides monomers (2,5-Dichlorobenzophenone and its derivatives) were first successfully synthesized from aluminum chloride-catalyzed, Friedel-Crafts acylation of benzene and various aromatic compounds with 2,5-dichlorobenzoyl chloride. These monomers were then polymerized via Ni (0)-catalyzed coupling reaction to form various high molecular weight substituted poly(2,5-benzophenone)s. Great care must be taken to achieve anhydrous and inert conditions during the reaction. A series of poly(2,5-benzophenone) activated aryl fluoride telechelic oligomers with different block molecular weights were then successfully synthesized by Ni (0)- catalyzed coupling of 2,5-dichloro-benzophenone and the end-capping agent 4-chloro-4'-fluorobenzophenone or 4-chlorophenly-4′-fluorophenyl sulfone. The molecular weights of these oligomers were readily controlled by altering the amount of end-capping agent. These telechelic oligomers (hydrophobic) were then copolymerized with phenoxide terminated disulfonated poly (arylene ether sulfone)s (hydrophilic) by nucleophilic aromatic substitution to form novel hydrophilic-hydrophobic multiblock copolymers. A series of novel multiblock copolymers with number average block lengths ranging from 3,000 to 10,000 g/mol were successfully synthesized. Two separate Tgs were observed via DSC in the transparent multiblock copolymer films when each block length was longer than 6,000 g/mol (6k). Tapping mode atomic force microscopy (AFM) also showed clear nanophase separation between the hydrophilic and hydrophobic domains and the influence of block length, as one increased from 6k to 10k. Transparent and creasable films were solvent-cast and exhibited good proton conductivity and low water uptake. These PAES-PBP multiblock copolymers also showed much less relative humidity (RH) dependence than random sulfonated aromatic copolymers BPSH 35 in proton conductivity, with values that were almost the same as Nafion with decreasing RHs. This phenomenon lies in the fact that this multiblock copolymer possesses a unique co-continuous nanophase separated morphology, as confirmed by AFM and DSC data. Since this unique co-continuous morphology (interconnected channels and networks) dramatically facilitates the proton transport (increase the diffusion coefficient of water), improved proton conductivity under partially hydrated conditions becomes feasible. These multiblock copolymers are therefore considered to be very promising candidates for high temperature proton exchange membranes in fuel cells. / Ph. D.

Poly(phenylene sulfide) (PPS), an engineering thermoplastic with excellent mechanical, thermal, and chemical properties, was gelled for the first time using 1,3-diphenylacetone (DPA) as the gelation solvent in a thermally induced phase separation (TIPS) process. PPS was dissolved in DPA at high temperatures to form a homogeneous solution. The solution was cooled, initiating phase separation and eventually forming a solidified PPS network around DPA-rich domains. Evacuation of DPA from the gel network creates monolithic PPS aerogels, one of few physically crosslinked polymer aerogel systems comprised of a high-performance thermoplastic. In this work, specific properties of PPS aerogels were controlled through the manipulation of various processing parameters, such as polymer concentration, post-process annealing conditions, mode of manufacturing (casting versus additive manufacturing), dissolution temperature, and drying method. The ultimate goal was to elucidate key process-morphology-property relationships in PPS aerogels, to ultimately improve aerogel performance and applicability. The phase diagram of PPS/DPA was first elucidated to determine the phase separation mechanism of the system, which guides all future processing decisions. The phase diagram indicated that the system undergoes solid-liquid phase separation, typical for solutions with relatively favorable polymer-solvent interactions. This assignment was validated by the calculation of the Flory-Huggins interaction parameter through two independent methods - Hansen solubility parameters and fitting melting point depression data. The influence of polymer composition on PPS aerogel properties was then characterized. As polymer concentration increased, aerogel density and mechanical properties increases, and porosity decreased. The particular morphology of PPS aerogels from DPA was that of a fibrillar network, where these axialitic (pre-spherulitic) fibrils are comprised of stacks of PPS crystalline lamellae, as suggested by x-ray scattering and electron microscopy. These interconnected microstructures responded more favorably to compressive load than similar globular PEEK aerogels, highlighting the importance of aerogel microstructure on its mechanical response. Upon solvent extraction, PPS aerogels were annealed in air environments to improve their mechanical behavior. Annealing did not dramatically shrink the aerogels, nor did it appear to affect the micron-scale morphology of PPS aerogels as observed by electron microscopy. The resistance to densification of PPS aerogels was mainly a product of their interconnected fibrillar morphologies, aided by subtle microstructural changes that occurred upon annealing. Exposure to a high temperature oxidative environment (160 – 240 oC) increased the degree of crystallinity of the aerogels, and also promoted chemical crosslinking within the amorphous PPS regions, both of which may have helped to prevent severe densification. With enhanced physical and chemical crosslinking, annealed PPS aerogels displayed improved compressive properties over unannealed analogues. Additionally, the thermal conductivity of both annealed and unannealed aerogel specimens was below that of air (~ 0.026 W/mK) and did not display a dependence on polymer composition nor on annealing condition. Generally, these experiments demonstrate that annealing PPS aerogels improved their mechanical performance without negatively affecting their inherent fibrillar morphology, low density, or low thermal conductivity. To fabricate aerogels with geometric flexibility and hierarchical porosity, PPS/DPA solutions were printed through material extrusion (MEX) and TIPS using a custom-built heated extruder. In this process, solid solvated gels were first re-dissolved in a heated extruder and solutions were deposited in a layer-wise fashion onto a room-temperature substrate. The large temperature gradient between nozzle and substrate rapidly initiated phase separation, solidified the deposited layers and formed a printed part. Subsequent solvent exchange and drying created printed PPS aerogels. The morphology of printed aerogels was compositionally-dependent, where the high extrusion temperature required to dissolve highly-concentrated inks (50 wt % PPS) also destroyed self-nuclei in solution, yielding printed aerogels with spherulitic microstructures. In contrast, aerogels printed from 30 wt % solutions were deposited at lower temperatures and demonstrated fibrillar microstructures, similar to those observed in 30 wt % cast aerogel analogues. Despite these microstructural differences, all printed aerogels demonstrated densities, porosities, and crystallinities similar to their cast aerogel counterparts. However, printed aerogel mechanical properties were microstructurally-dependent, and the spherulitic 50 wt % aerogels were much more brittle compared to the fibrillar cast 50 wt % analogues. This work introduces a widely-applicable framework for printing polymer aerogels using MEX and TIPS. Intrigued by the compositional morphological dependence of the printed PPS aerogels, the dissolution temperature (Tdis), and thus the self-nuclei content, of cast PPS/DPA solutions was systematically varied to understand its influence on aerogel morphology and properties. As Tdis increased, the length and diameter of axialites increased while aerogel density and porosity were relatively unaffected. Thus, the isolated influence of axialite dimensions (analogous to pore size and pore concentration) on aerogel properties could be studied independent of density. At low relative densities (below 0.3, aerogels of 10 – 30 wt %), compressive modulus and offset yield strength tended to decrease with Tdis, due to an increase in axialite length (akin to pore size) and number of axialites (akin to number of pores). At higher relative densities (above 0.3, 40 and 50 wt %), axialitic aerogels were so dense that changes in pore dimensions did not result in systematic changes in mechanical response. All spherulitic aerogels fabricated at the highest Tdis¬ demonstrated reduced mechanical properties due to poor interspherulitic connectivity. The thermal conductivity of all aerogels increased with polymer composition but demonstrated no clear trend with Tdis. A model for thermal conductivity was used to deconvolute calculated conductivity into solid, gaseous, and radiative components to help rationalize the measured conductivity data. This work demonstrates the importance of nucleation density control in TIPS aerogel fabrication, especially at low polymer concentrations. The specific method used to dry an aerogel generally has a great influence on its microstructure and density. Vacuum or ambient drying is the most industrially-attractive technique due to low cost and low energy usage; however, it is typically the most destructive process due to high capillary forces acting on the delicate aerogel microstructure. Three drying methods, vacuum drying, freeze drying, and supercritical CO2 drying, were used to evacuate PPS gels fabricated at three PPS concentrations (10, 15, and 20 wt %). Almost all aerogel specimens displayed excellent resilience against shrinkage as a function of the drying method, besides the 10 wt % vacuum dried sample which shrunk almost 40%. While the micron-scale aerogel morphology captured by electron microscopy appeared to be unaffected by the drying method, other properties such as aerogel surface area, mesoporous volume, and mechanical properties were effectively functions of the degree of aerogel shrinkage. Aerogel thermal conductivity was low for all samples, and in particular, vacuum dried aerogels demonstrated slightly lower conductivities than other ambiently-dried aerogel systems such as silica and carbon. In general, vacuum drying appears to be industrially viable for PPS aerogels at concentrations above 10 wt %. / Doctor of Philosophy / Polymer aerogels are nanoporous solid networks of low density. These materials are used in applications such as thermal insulation, absorbance/filtration, drug delivery, biomedical scaffolds, solid state batteries, and others. One method of creating polymeric aerogels is through thermally induced phase separation (TIPS), where a polymer is first dissolved in a high boiling point solvent at a high temperature. Next, the solution is cooled, inducing phase separation and gelation. Extraction of the gelation solvent transforms the solvated gel into an aerogel. To create polymeric aerogels with good properties and wide-ranging applicability, one should use a high-performance polymer. In this work, aerogels are for the first time made from poly(phenylene sulfide) (PPS), an engineering thermoplastic with good mechanical properties, thermal stability, and chemical resistance. PPS aerogels are fabricated using TIPS over a wide compositional range, and their microstructures, physical properties, thermal properties, and compressive properties are fully characterized. To further enhance aerogel performance, the fabrication process can be optimized to precisely control the aerogel morphology and thus the resulting properties. The influence of processing variables such as the polymer concentration, the post-fabrication aerogel annealing conditions, the method of manufacturing (traditional casting versus additive manufacturing), the dissolution temperature (temperature at which the polymer dissolves in solution prior to gelation), and the drying method on the aerogel behavior is investigated. Generally, results suggest that understanding critical process-morphology-property relationships allows for precise control over the nature of PPS aerogels.

O poli (p-fenilenevinileno), ou PPV, é um polímero de grande relevância tecnológica devido a suas propriedades eletroluminescentes, que têm sido exploradas em diodos emissores de luz orgânicos, displays flexíveis e outros dispositivos optoeletrônicos. Embora o PPV seja um material de importância para muitas aplicações, a sua síntese na nano/microescala não pode ser obtida através do método padrão, o qual utiliza o aquecimento de um polímero precursor poli (cloreto de xileno tetrahidrotiofenio) (PTHT). Este trabalho mostra como a microestruturação com pulsos de femtosegundo pode ser empregada para a síntese de PPV em regiões pré-determinadas, empregando três diferentes abordagens, permitindo uma nova metodologia para a fabricação precisa de microcircuitos poliméricos complexos, (i) na primeira abordagem, o processo de conversão é obtido pela irradiação de filmes de PTHT com pulsos laser ultracurtos em regiões previamente determinadas, o que leva ao controle espacial da formação de PPV em microescala, (ii) na segunda abordagem, microestruturas tridimensionais dopadas com PTHT foram fotopolimerizadas por absorção de dois fótons. A conversão de PTHT para PPV nestas microestruturas dopadas foi obtida após um tratamento térmico, (iii) na terceira abordagem, a transferência direta induzida por laser (LIFT) com pulsos de femtossegundos permite a deposição controlada de PPV com alta resolução espacial, fornecendo micropadrões 2D, preservando sua estrutura e propriedades ópticas. As estruturas foram caracterizadas por microscopia eletrônica de varredura, microscopia óptica de transmissão, microscopia de fluorescência e microscopia confocal de fluorescência. Suas propriedades ópticas foram analisadas através de sistemas de micro-fotoluminescência e micro-absorção implementadas em um microscópio invertido. Medidas de espectroscopia Raman, microscopia de força atômica e medidas elétricas também foram realizadas. Este trabalho mostra como a microestruturação com laser de fs pode ser explorada para a síntese de PPV em regiões pré-determinadas para fabricar uma variedade de microdispositivos, abrindo novos caminhos na optoeletrônica baseada em polímeros. / Poly(p-phenylenevinylene), or PPV, is a polymer of great technological relevance due to its electroluminescent properties, which have been exploited in organic light emitting diodes, flexible displays and other optoelectronic devices. Although PPV is a material of foremost importance for many applications, its synthesis at the nano/micro scale cannot be achieved through the standard method that uses heating of a precursor polymer poly(xylene tetrahydrothiophenium chloride)(PTHT). This work demonstrates the use of direct laser writing with femtosecond pulses to obtain the synthesis of PPV in pre-determined regions, by applying three different approaches, allowing the precise fabrication of complex polymeric microcircuits, (i) in the first approach the conversion process is achieved by irradiating PTHT films with ultra-short laser pulses in previously determined regions, which leads to the spatial control of PPV formation at microscale, (ii) in the second approach, three-dimensional microstructures doped with PTHT were photopolymerized by two photons absorption. The conversion of PTHT to PPV in these doped microstructures was obtained by a subsequent thermal treatment, (iii) in the third approach, laser-induced forward transfer (LIFT) with femtosecond pulses enables the controlled deposition of PPV with high spatial resolution, providing 2D micropatterns, while preserving its structure and optical properties. The structures were characterized by scanning electron, fluorescence, transmission and confocal fluorescence microscopies. Their optical properties were analyzed by micro-photoluminescence and micro-absorption setups assembled on an inverted microscope. Raman spectroscopy, electrical measurements and atomic force microscopy were also performed. This thesis shows the use of fs-laser writing methods for the synthesis of PPV in pre-determined regions, to fabricate a variety of microdevices, thus opening new avenues in polymer-based optoelectronics.

Wir haben blau, grün und orange leuchtende organische Nanofäden oder Nanonadeln und Mikroringe aus para-Hexaphenyl (p-6P), alpha-Quaterthiophen (alpha-4T) und alpha-Sexithiophen (alpha-6T) mittels Organischer Molekularstrahlepitaxie (OMBE) auf Muskovit Glimmer hergestellt. Die Aggregate haben wir mit der Atomkraftmikroskopie, mit der Fluoreszenz-Mikroskopie und durch UV-vis Spektroskopie charakterisiert. Auf der Muskovit Oberfläche wachsen p-6P Fäden parallel zueinander auf und zeigen zwei verschiedene Orientierungsdomänen entlang [110] und [1-10]. Mit Hilfe einer systematischen statistischen Analyse diskutieren wir das Wachstum dieser p-6P Nadeln für verschiedene Wachstumsbedingungen. Zusätzlich zu den Fäden haben wir p-6P Cluster auf der Oberfläche beobachtet. Nadeln werden durch die Aggregation solcher Cluster gebildet. Ein Realraummodell der Morphologie der Nadeln sowie ein Modell für deren Wachstum werden vorgestellt. Indem wir Glimmer zunächst mit einer dünnen Goldschicht bedecken und die Wachstumsparameter variieren, erreichen wir eine weitgehende Kontrolle der Morphologie der Nadeln (Länge von 0,5 Mikrometer bis 1 mm, Höhe von 25 bis 300 nm und Breite von 100 bis 600 nm). Im Gegensatz zu p-6P orientieren Thiophene ihre Wachstumsrichtungen an allen hoch symmetrischen Richtungen von Glimmer. Es wird gezeigt, dass die Mechanismen für das Fadenwachstum von beiden Oligomere gleich sind, nämlich eine Kombination aus Epitaxie und einer Dipol-unterstützten Ausrichtung. Auch die Strukturen dieser Fäden sind ähnlich: die Moleküle liegen parallel angeordnet auf der Oberfläche, ihre Längsachsen orientieren sich schräg zur Längsachse der Fäden. Auf mit Wasser oder Methanol vorbehandeltem Glimmer wachsen diese beiden Oligomere als gebogene Fäden und Mikroringe auf. Diese Oberflächenvorbehandlungen sowie das Wachstum von p-6P auf Gold/Glimmer unterstützen auch den Wachstumsmechanismus auf der sauberen Glimmer-Oberfläche. / By using organic molecular beam epitaxy (OMBE) blue, green and orange light emitting organic nanofibers or nanoneedles and microrings from para-hexaphenyl (p-6P), alpha-quaterthiophene (alpha-4T) and alpha-sexithiophene (alpha-6T), respectively, on muscovite mica surfaces are generated. The aggregates are characterized by atomic force microscopy, fluorescence microscopy and UV-vis spectroscopy. On muscovite mica, p-6P fibers usually grow mutually parallel showing two domains of their orientations with an angle of 120 degree in between. The detail growth of nanofibers from p-6P by performing a systematic statistical analysis of fibers as a function of various growth conditions is discussed. Furthermore, the morphology exhibits p-6P clusters, which are found to be fibers´ building blocks. A real space model of the fiber and a model for their growth are also presented. By introducing a thin gold layer on mica prior to p-6P deposition together with varying growth parameters, the morphology of fibers is controlled in a wide range (length from 0.5 micrometer to 1 mm, height from 25 to 300 nm and width from 100 to 600 nm). In contrast to p-6P, thiophene fibers exhibit various orientations close to mica high symmetry directions. It is shown that the mechanism behind the fiber growth from all molecules on mica is the same, i.e. a combination of epitaxy and dipole assisted growth process. The fiber microscopic structures are similar, too: molecules take lying orientations and they hold themselves parallel pointing their long axes along an oblique direction off the long fiber axis. The growth of both types of oligomers on water or methanol treated mica surfaces leads to the formation of bent fibers and microrings. This surface pretreatment and the growth of p-6P on gold/mica support the fiber growth mechanism on plain mica.

In this thesis, we investigated several photoelectric material systems consisted of conjugated polymers by means of computer simulation. We combined several theory and simulation methods to meodeling different subjects from atomic to mesoscopic scale. We dealt with the problems such as quantum efficiency, structure characteristic, and the phase behavior in material. We hope to have better understanding of the relationship between structure characteristic and functional property in material. It will help an engineering designer to adjust the variables that optimize characteristics linking the synthesis of advanced materials with desired physical properties. This work can be divided into three parts. Long side chain substituted PPV polymers applied in light-emitting diode material : Molecular dynamics simulations were employed to investigate structure features and segment orientation of four poly(phenylene vinylene) (PPV)-like conjugated polymers with long flexible side chains at room temperature. In the simulations, the main chains of the polymers were found to be semi-rigid and to exhibit a tendency to coil into ellipsoidal helices or form zigzag conformations of only limited regularity. It was shown that continuous segments of a chain which are quasi-coplanar along the backbone are in a range of 2~4 repeat units. This implies that long-range electron transfer along same backbones of these polymers may not happen but may be mediated by interchain interactions. The ordered orientation and coupling distance of interchain aromatic rings are found to correlate with important optical properties of materials. Then we combined molecular dynamics simulation and density matrix methods modeling of amorphous light-emitting polymers. A simplified method combining molecular dynamics (MD) simulation and density matrix (DM) theory was developed for the prediction of optical properties of long side chain substituted poly(phenylene vinylene) (PPV) polymers. This MD+DM method takes account of the complexity of molecular packing of polymer chains. The method has been tested to simulate the absorption spectra of four model systems. The wavelengths of absorption maxima of the calculated spectra of these four conjugated polymers are in reasonable agreement with experimental data. The simulation also demonstrated that the importance of including interchain interactions in the calculation. Ion-conducting polymer sPBI-PS(Li+): To understand the mechanism of ionic migration in the amorphous matrixes of polymer electrolytes is crucial for their applications in modern technologies. Here, molecular dynamics (MD) simulation was carried out to investigate the ionic conduction mechanism of a particular conjugated rigid-rod polymer, sPBI-PS(Li+). The backbone of this polymer is poly[(1, 7- dihydrobenzo[1, 2-d:4,5-d¡¦]diimidazole- 2,6-diyl)-2-(2-sulfo)-p-phenylene]. The polymer has pendants of propane sulfonate Li+ ionomer. The MD simulations showed that the main chains of sPBI-PS(Li+) are in layer-like structure. The further detailed structure analysis suggested that the £k-electron of this polymer is not delocalized among aromatic rings. This agrees with the experimental result that sPBI-PS(Li+) shows no electronic conductivity and the conductivity of this polymer is mainly ionic. The calculated migration channels of lithium ions and electrostatic potential distributions indicated clearly that the polymer matrix is anisotropic for the migrations of ions. The migration of lithium ions along the longitudinal direction is more preferable than that along the transverse direction. The relaxations of the polymer host were found to play important roles in the transfer process of lithium ions. The hopping of lithium ion from one -SO3-1 group to another is correlated strongly with characteristic motions of -SO3-1 group on a time scale of about 10-13 s. Self-assembly functional material. Dissipative particle dynamics (DPD) simulations were carried out to investigate mixed ionic and non-ionic molecules, sodium tetradecyl sulfate (STS) and tetradecyl triethoxylated ether (C14E3) aqueous system. Different types of mixed micelles are formed depending on the concentrations of STS and C14E3. Our results are in good agreement to the early NMR measurements. From the investigation of surfactant aggregation, we understand the self-assembly mechanism and classical phase behavior in general diblock copolymer. Further, we investigated the self-assembly process on a particular mushroom-shaped supramolecular film material from molecular character to phase behavior. The miniaturized rod-coil triblock copolymers (PS-PI-RCBC) HEMME had been found to self-assemble into well-ordered nanostructures and unusual head to tail multilayer structure. The purpose of our study is to obtain fundamental understanding the connection of the inherent morphological characterization of single molecule and the mechanism of phase behavior of this polar self-assembly system. Dissipative particle dynamics simulation was carried out to study the mechanism of phase behavior of the solvent-copolymers system. We found that the solvent-induced polar effect under different temperature is important in the process of self-assembly of block copolymers. In different temperature the solvent induces hybrid structure aggregation. Our results are consistent with experimental observations and give evidence for a special mechanism governing the unusual phase behavior in thin films of modulated phases. The sizes and stabilization energies of mushroom-shaped supramolecular clusters were predicted by molecular modeling method. Clusters of sizes from 16 to 90 molecules were found to be stable. In combination of classical and simple quantum mechanical calculations, the band gaps of HEMME clusters with various sizes were estimated. The band gap was converged at 2.45 eV for cluster contains 90 molecules. Nonlinear optical properties of the material were investigated by the semi-empirical quantum mechanical calculations of molecular dipole moment and hyperpolarizabilities. Significant second-order nonlinear optical properties were shown from these calculated properties.

There are two general ways to introduce functionalities into a polymeric structure: functionalization of the monomeric units before polymerization and postfunctionalization of the preformed polymer. Building libraries of polymers with different functionalities can be completed with significantly less effort by the second method, as each postfunctionalization of a single batch of polymeric backbone can involve as little as one synthetic step. One method of building a polymeric backbone for postfunctionalization involves the synthesis of hyperbranched conjugated polymers (HCPs) from AB2 monomeric units. A polymer formed from n AB2 monomeric units should contain n reactive B groups, which act as sites of functionalization. Utilizing this principle, two different hyperbranched poly(phenylene vinylene-phenylene ethynylene) scaffolds were synthesized and studied in both their inherent properties and functionalization. The first HCP synthesized was compared against a monomeric cruciform model and a linear polymer with a similar structure. The hyperbranched polymer has red-shifted absorption and emission in comparison to the cruciform model and linear polymer. The HCP quenches paraquat more efficiently than the linear polymer by a factor of about two, suggesting a greater rate of energy transfer. The functionalization of HCPs was studied; iodine groups decorating the HCPs were replaced with terminal alkynes by Pd-catalyzed coupling, providing a library of 24 differently functionalized HCPs. Elemental analyses of the postfunctionalized polymers show nearly complete substitution of the iodine groups. The postfunctionalized polymers show increased fluorescence compared to the original iodine decorated polymers, due to the loss of the heavy atom effect inducing iodine groups. The emissions of the postfunctionalized polymers in solution show a strong dependence on the groups attached to the conjugated structures, with emission maxima ranging from 505 nm to 602 nm; quantum yields range from 0.7% to 25%. Solid-state emission studies show stronger and more red-shifted spectra compared to emissions observed in solution.