Partículas e filmes híbridos de polímeros e compostos de amônio quaternário (CAQ) foram caracterizados quanto a propriedades físicas e atividade contra cepas de Pseudomonas aeruginosa ATCC 27853 e Staphylococcus aureus ATCC 25923. Partículas híbridas foram obtidas a partir de fragmentos de bicamada (BF) de brometo de dioctadecildimetilamônio (DODAB), adicionados consecutivamente de soluções de carboximetilcelulose (CMC) e cloreto de poli (dialildimetilamônio) (PDDA) e, a seguir, caracterizadas por espalhamento de luz dinâmico para determinação de distribuições de tamanho, diâmetro médio (Dz) e potencial-zeta (ζ). Filmes híbridos foram obtidos por revestimento rotacional de lamínulas de vidro a partir de uma solução clorofórmica de poli (metil metacrilato) (PMMA) e CAQ onde [PMMA] = 10 mg/mL e [CAQs] = 0,03 4 mM de DODAB, brometo de cetiltrimetilamônio (CTAB) ou brometo de tetrapropilamônio (TPAB). Molhabilidade dos filmes e difusibilidade dos CAQs nos filmes imersos em água foram avaliadas por determinação de ângulo de contato e de tensão superficial na interface ar-água, respectivamente. Atividade antimicrobiana foi avaliada por plaqueamento e contagem de viáveis, tanto para os filmes quanto para as partículas. Para os filmes, também foram determinados halos de inibição. Partículas de DODAB BF/ CMC/ PDDA exibiram Dz e ζ dependentes da concentração dos componentes. A 0,1 mM de DODAB, 0,1 mg/mL de CMC e 0,1 mg/mL de PDDA, foram obtidas partículas pequenas (Dz = 100 nm; ζ = 30 mV). Com 0,5 mM de DODAB, 0,5 mg/mL de CMC e 0,5 mg/mL de PDDA foram obtidas partículas grandes (Dz = 470 nm; ζ = 50 mV). Contra 107 UFC/mL, 1 - 2 µg/mL de PDDA, sozinho em solução ou em forma de partículas, matou 99 % das células de P. aeruginosa. O mesmo ocorreu contra S. aureus (107 UFC/mL) em 10 µg/mL de PDDA. A ação antimicrobiana mostrou-se dependente da quantidade de cargas positivas nas partículas e independente do tamanho da partícula. Filmes de PMMA/ CAQ apresentaram maior molhabilidade do que aqueles de PMMA puro. Filmes de PMMA/ DODAB e PMMA/ TPAB submersos em água não causaram alterações de tensão superficial na interface ar-água, indicando baixa difusibilidade destes CAQs a partir dos filmes. Filmes de PMMA/ CTAB submersos em água reduziram a tensão superficial até aproximadamente 60 mN/m, mostrando a difusibilidade do CTAB no filme e sua organização na interface ar-água. O efeito antimicrobiano dos filmes PMMA/ DODAB e PMMA/ CTAB foi dependente da concentração do CAQ utilizada no preparo do filme. Viabilidade celular de 0% contra 107 UFC/mL de ambas as bactérias ocorreu com 4 mM de DODAB ou, com 2 ou 0,2 mM de CTAB contra P. aeruginosa ou S. aureus, respectivamente. Filmes de PMMA/ TPAB não apresentaram atividade antimicrobiana. Com a emergência de micro-organismos resistentes aos antibióticos, os novos nanomateriais antimicrobianos híbridos de polímeros e compostos de amônio quaternário podem representar uma alternativa de fácil obtenção e baixo custo. / Hybrid particles and films from polymers and quaternary ammonium compounds (QAC) were characterized regarding its physical properties and antimicrobial activity against strains of Pseudomonas aeruginosa ATCC 27853 or Staphylococcus aureus ATCC 25923. Hybrid particles were obtained from dioctadecyldimethylammonium bromide (DODAB) bilayer fragments (BF), consecutively added of carboximethylcellulose (CMC) and poly (diallyldimethylammonium) chloride (PDDA) solutions, and then, characterized by dynamic light-scattering for determination of size distributions, z-average diameter (Dz) and zeta-potential (ζ). Hybrid films were obtained by spin-coating of a chloroformic solution of poly (methylmethacrylate) (PMMA) and QAC on glass coverslips at [PMMA] = 10 mg/mL and [QACs] = 0.03 -4 mM where QACs were DODAB, cetyltrimethylammonium bromide (CTAB) or tetrapropylammonium bromide (TPAB). Films wettability and QACs diffusibility in the films immersed in water were evaluated by determinations of contact angle and surface tension at air-water interface, respectively. Antimicrobial activity was evaluated by plating and CFU counting both for particles and films. For the hybrid films, width of inhibition zone was also determined. DODAB BF/ CMC/ PDDA particles exhibited Dz and ζ dependent on the concentrations of the components. At 0.1 mM DODAB, 0.1 mg/mL CMC, and 0.1 mg/mL PDDA, small cationic particles were obtained (Dz = 100 nm; ζ = 30 mV). At 0.5 mM DODAB, 0.5 mg/mL CMC and 0.5 mg/mL PDDA, large cationic particles were obtained (Dz = 470 nm; ζ = 50 mV). At 107 CFU/mL, cell viability of 1 % for P. aeruginosa was obtained for PDDA in solution or covering particles at 1 or 2 µg/mL PDDA, respectively. Against S. aureus (107 CFU/mL) at 10 µg/mL PDDA, a similar result was obtained. The antimicrobial effect was dependent on the amount of positive charge on particles and independent on particle size. The hybrid films of PMMA/ QAC showed higher wettability than those of pure PMMA. PMMA/ DODAB and PMMA/ TPAB hybrid films, submerged in water, did not cause changes in surface tension at the air-water interface, indicating low diffusibility for both DODAB and TPAB in hybrid films. Films of PMMA/ CTAB, submerged in water, reduced the surface tension to about 60 mN/m, showing that CTAB could diffuse from the film to the air-water interface and change its surface tension. The antimicrobial effect of PMMA/ DODAB and PMMA/ CTAB hybrid films was clearly dependent on the QAC concentration used to prepare the films. Cell viability of 0% for P. aeruginosa and S. aureus (107 CFU/mL) occurred at 4 mM DODAB, or 2 and 0.2 mM CTAB, respectively. Films of PMMA/ TPAB showed no antimicrobial activity. With the emergence of microorganisms resistant to antibiotics, the novel hybrid antimicrobial nanomaterials may become important since they are inexpensive and easy to obtain.

Le confinement de la matière condensée dans un milieu nanoporeux peut induire à l'échelle nanométrique des changements structurels ou dynamiques drastiques qui conduisent finalement aux propriétés originales. Le confinement des polyélectrolytes, qui sont des polymères porteurs d'une charge électrique, présente un intérêt particulier. Dans ce projet, des membranes d'alumine nanoporeuse auto-ordonnée (nPAAMs), dont les paramètres structuraux sont réglés par la synthèse, ont été choisies comme milieu de confinement et des approches expérimentales ont été proposées pour étudier le confinement d'un polyélectrolyte fort (PE), polystyrène-sulfonate de sodium. Une partie importante de ce travail a été consacrée à la caractérisation des charges structurales et superficielles des nPAAMs. La structure et la composition du nPAAM sont caractérisées par la combinaison de la microscopie électronique à balayage et de la diffusion neutronique à petit angle (SANS). Une stratégie détaillée est proposée pour mesurer les nPAAM dans des conditions optimales en raison de leur forme anisotrope et de leur pouvoir de diffusion élevé ainsi que des informations sur leur composition chimique. La charge superficielle de la membrane a été déterminée par des mesures de potentiel d’écoulement. La charge de la paroi du pore peut être ajustée à une charge positive ou négative et l'étendue des interactions électrostatiques peut être ajustée, ce qui permet d'adapter le milieu aux études de confinement électrostatique. Le comportement de perméation et l'adsorption du polyélectrolyte à l'intérieur des pores sont étudiés par SANS en combinaison avec des mesures de perméabilité. La cinétique de l'adsorption est obtenue par le potentiel d’écoulement et la possibilité d'utiliser la réflectivité neutronique pour ces études est proposée. Ce travail fournit des approches expérimentales sur la caractérisation de l'PE en milieu confiné. / The confinement of condensed matter in nanoporous medium can induce at the nanoscale drastic structural or dynamical changes that ultimately lead to original properties. Of a specific interest is the confinement of polyelectrolytes that are polymers carrying an electrical charge. In this project, self-ordered nanoporous alumina membranes (nPAAMs), whose structural parameters are tuned through the synthesis, have been chosen as a confining medium and experimental approaches have been proposed to study the confinement of a strong polyelectrolyte (PE), sodium polystyrene-sulfonate . An important part of this work has been devoted to the structural and surface charge characterization of nPAAMs. The nPAAM’s structure and composition are characterized by combining scanning electron microscopy and small angle neutron scattering (SANS). A detail strategy is proposed for measuring the nPAAMs under optimal conditions due to their anisotropic shape and high scattering power and information on their chemical composition. The membrane’s surface charge has been determined by streaming potential measurements. The pore’s wall charge can be adjusted to positive or negative charge and the extent of the electrostatic interactions can be tuned, tailoring the medium for electrostatic confinement studies. The permeation behavior and the adsorption of the polyelectrolyte inside the pores is studied by SANS combined with flow measurements. The kinetics of the adsorption is accessed by streaming potential and the possibility to use of neutron reflectivity for such studies is proposed. This work provides experimental approaches insight into the characterization of PE under confinement.

Die ellipsometrische Lichtstreuung wird als eine neue, leistungsfähige Methode zur Charakterisierung von Schichten um kolloidale Partikel vorgestellt. Theoretische Grundlage der Methode ist die Mie-Theorie der Lichtstreuung. Experimentell wurde die Polarisationsoptik eines Null-Ellipsometers in den Strahlengang eines Lichtstreuaufbaus eingebaut. Wie in der Reflexionsellipsometrie um den Brewsterwinkel herum erhält man in der ellipsometrischen Streuung einen Winkelbereich, in dem die Methode empfindlich auf Schichten an der Oberfläche der Partikel ist. An verschiedenen Systemen wurde die Tauglichkeit der ellipsometrischen Streuung zur Charakterisierung von Schichten auf Partikeln demonstriert. So wurden Dicke und Brechungsindex einer thermosensitiven Schicht von Poly(N-isopropylacrylamid) auf einem Poly(methylmethacrylat)-Kern bestimmt. Damit ist es möglich, experimentell den Schichtbrechungsindex und damit den Quellungsgrad zu bestimmen. Des Weiteren wurde der Einfluss der NaCl-Konzentration auf die Polyelektrolythülle von Poly(methylmethacrylat)-Poly(styrolsulfonat)-Blockcopolymer-Partikeln untersucht. Die Polyelektrolytketten liegen im hier untersuchten Beispiel nicht gestreckt vor. Als drittes wurde die Verteilung von niedermolekularen Ionen um elektrostatisch stabilisierte Poly(styrol)-Latexpartikel in Wasser untersucht. Hier wurde gezeigt, dass die beobachteten Schichtdicken und Schichtbrechungsindizes viel größer sind, als nach der klassischen Poisson-Boltzmann-Theorie zu erwarten ist. Des Weiteren wurde die Doppelbrechung von unilamellaren Lipidvesikeln bestimmt. Außerdem wurden Messungen der dynamische Lichtstreuung im Intensitätsminimum der Ellipsometrie durchgeführt. Dabei wird ein Prozess mit einer Korrelationszeit, die unabhängig vom Streuvektor, aber abhängig von der verwendeten Wellenlänge ist, sichtbar. Die Natur dieses Prozesses konnte hier nicht vollständig geklärt werden. / Ellipsometric light scattering is introduced as a new and powerful technique to characterize layers on colloidal particles. For the experiments, the polarization optics used reflection ellipsometry was installed in the beam of a light scattering setup. Using the priciples of null ellipsometry, a small range of scattering angles is obtained, were the method is sensitive to layers on the surface of colloidal particles. This is an analogy to the layer sensitivity of reflection ellipsometry at planer interfaces close to the Brewster angle. The theoretical basis for ellipsometric scattering is the Mie theory with its modern supplements. The feasibility of characterizing layers on colloidal particles was demonstrated with several systems. First, layer thickness and layer refractive index of poly(N-isopropylacrylamide) layers on a poly(methylmethacrylate) core were determined. This was the first time that the refractive index and with that the degree of swelling of a layer was directly determined in an scattering experiment. Second, polyelectrolyte layers on Poly(methylmethacrylate)-Poly(styrenesulfonate)-blockcopolymer particles were characterized. The influence of the salt concentration on the parameters of the layer was determined. The results show that the polyelectrolyte chains in the system investigated are not streched. Third, layers of ions around electrostatically-stabilized poly(styrene) particles were characterized. The layer thickness and layer refractive index in these examples are shown to be much larger than predicted by the classical Poisson-Boltzmann-theory. In addition, the birefringence of lipid vesicles was determined. Another interesting application of the ellipsometric scattering is the dynamic light scattering with ellipsometric optics. Its results show a characteristic process with a correlation time independent of the scattering vector, but wavelength dependent. The origin of this mode is not yet completely clarified.

Defect generation and propagation in thin films, such as separation membranes, can lead to premature or catastrophic failure of devices such as polymer electrolyte membrane fuel cells (PEMFC). It is hypothesized that defects (e.g., air bubbles, pin-holes, and holes) originate during the manufacturing stage, if precise control is not maintained over the coating process, and they propagate during system operation. Experimental and numerical studies were performed to detect and eliminate defects that were induced during slot die coating of high-viscosity (1 to 40 Pa-s), shear-thinning solutions. The effects of fluid properties, geometric parameters and processing conditions on air entrainment and coating windows (limited set of processing conditions for which defect-free coating exists) were studied. When smaller slot gaps and coating gaps were used, relatively small bubbles were entrained in the coated film. The air bubble sizes increased as the viscosity of the coating solution decreased. A semi-empirical model correlating the maximum coating speed to a solution's material properties, geometric parameters and processing conditions was developed. Such a predictive model will enable engineers to determine the maximum coating boundary for shear-thinning and Newtonian solutions within certain constraints. Smaller coating gaps and low-viscosity solutions produced higher coating speeds. The surface tension property of the coating solution provided stability to the coating bead. Therefore, solutions with higher surface tension could be processed at higher coating speeds.

The mechanism through which a charged polymer cationic polyacrylamide (C-PAM) operates to increase the rate of cornstarch hydrolysis was investigated. The main objective was to determine the major factors that affect the mechanism so that these parameters may be adjusted to achieve optimal hydrolysis rates. A combination of analytical methods including dynamic light scattering, optical imaging, and uv-vis spectroscopy were used to study polymer, starch, and enzyme interactions as a function of process conditions. It was found that C-PAM binds strongly to starch granules, increasing solubilization and decreasing onset gelatinization temperature. Granule swelling was unaffected by C-PAM. Both binding of enzyme to cornstarch, and rate of cornstarch hydrolysis were found to increase in the presence of C-PAM. By analogy to previous work on cationic polymer promoted hydrolysis of cellulose, it was proposed that the polymer reduces the charge on the starch surface through a "charge-patch" mechanism. Because both enzyme and substrate are negatively charged, the positively charged polymer reduces the charge repulsion experienced by the approaching enzyme. This leads to stronger enzyme-substrate binding, and faster hydrolysis. There is a mirror image relationship between viscosity of the medium and hydrolysis rate, which allows optimization of these parameters with enzyme and C-PAM dosage. Overall, the polymer addition reduced enzyme dose by 62% depending on the conditions used, so this method could have significant economic impact on the industrial conversion of starch to ethanol.

Several analytical mean field models are presented for the class of stimuli responsive polymers that are driven by the lower critical solution temperature (LCST) transition. For solutions above the polymer crossover concentration, a hybrid model combines lattice-fluid excluded volume and van-der-Waals interactions with a combinatorial approach for the statistics of hydrogen bonding, hydration, and ionic bonding. This approach yields models for the LCST of both neutral polymers and lightly charged polyelectrolytes in aqueous salt solution. The results are shown to be in semi-quantitative agreement with experimental data for the cloud point of polyethylene oxide (PEO) in aqueous solution with various salts, and some aspects of the lyotropic series are reproduced. Results for lightly charged polyelectrolytes are compared to and shown to be in qualitative agreement with aspects of experimentally observed behavior. Finally, a framework is established for extension of these models to further aspects of the lyotropic series and polyelectrolyte behavior. At the nanoscale, lattice fluid (LF) and scaled particle theory (SPT) approaches are employed to model the LCST-related coil-globule-transition (CGT) of isolated polymer chains in highly dilute solution. The predicted CGT behavior semi-quantitatively correlates with experimental results for several polymer-solvent systems and over a range of pressures. Both the LF and SPT models exhibit a heating induced coil-to-globule transition (HCGT) temperature that increases with pressure until it merges with a cooling induced coil-to-globule transition (CCGT). The point at which the CCGT and HCGT meet is a hypercritical point that also corresponds to a merging of the lower critical and upper critical solution temperatures. Theoretical results are discussed in terms of a generalized polymer/solvent phase diagram that possesses three hypercritical points. Within the lattice model, a dimensionless transition temperature [author gives mathematical symbol] is given for a long chain simply by the equation [author gives mathematical equation], where [part of the equation] is the bulk solvent occupied volume fraction at the transition temperature. Furthermore, there is a critical value of the ratio of polymer to solvent S-L characteristic temperature below which no HCGT transition is predicted for an infinite chain. / text

Vienas iš šiuolaikinės polimerų chemijos uždavinių – gauti numatytos molekulinės masės ir architektūros polimerines medžiagas. Neseniai buvo sukurti nauji radikalinės polimerizacijos metodai, kurie priskiriami gyvybingajai (valdomai) polimerizacijai (GRP). Makromonomerų (MM) gyvybingoji radikalinė polimerizacija yra efektyvus būdas gauti šepetinius (cilindrinius) polimerus). Šepetiniai polimerai – tai makromolekulės, kuriose prie pagrindinės polimerinės grandinės prijungta daug šoninių mažesnės molekulinės masės polimerinių (oligomerinių) grandinių. Dėl tarp šoninių grandinių esančių erdvinės stūmos jėgų tokios makromolekulės įgauna neįprastų savybių, pvz., standumą, cilindrinę formą, didelį segmentų tankį. Pagrindinis šio darbo tikslas buvo susintetinti norimos sudėties šepetinius polielektrolitinius polimerus, sudarytus iš krūvį turinčios poli(met)akrilato pagrindinės grandinės ir šoninių polietilenoksido grandinių, ir ištirti jų savybes. Svarbiausieji šio darbo rezultatai, atspindintys jo naujumą, originalumą ir svarbą: Pirmą kartą nuodugniai ištirta metakrilo rūgšties (MAR) ir dviejų skirtingų molekulinių masių polietilenoksido metakrilatų PEOnMEMA (n = 5, 45) kopolimerizacija įprastiniu radikaliniu ir RAFT metodais. Sukurta metodika PEO makromonomerų kopolimerizacijos kinetikai tirti, užrašant 1H BMR spektrus in situ ir įvertinant likutinę monomerų koncentraciją reakcijos mišinyje bei momentinę kopolimero sudėtį iki gilių konversijų. Netiesiniu kintamųjų paklaidų metodu... [toliau žr. visą tekstą] / The main goal of this work was to synthesize polyelectrolyte brushes containing poly(ethylene oxide) side chains by living polymerization. Brush-like macromolecules are unique polymer molecules whose conformation and physical properties are controlled by steric repulsion of densely grafted side chains. Molecules can be either flexible or stiff, depending on the grafting density and the length of the side chains. Polymerization of macromonomers is one of the most useful ways to prepare brush copolymers. However, with the macromonomer method, the distribution of the spacing of the side chains cannot be entirely controlled which along with broad and multimodal molecular weight distribution makes these polymers heterogeneous. These problems were considered to be overcome with the use of controlled/living polymerization. Conventional free-radical and RAFT copolymerization of poly(ethylene oxide) substituent containing methacrylate macromonomers, PEO5MEMA and PEO45MEMA, with methacrylic acid (MAA) was studied by the use of 1H NMR spectroscopy for an analysis of residual monomers. RAFT copolymerization of PEO45MEMA and MAA enabled to synthesize comb copolymers with low composition distribution and more homogeneous distribution of PEO side chains along the mainchain. Amphiphilic non-ionic blockcopolymers poly(lauryl methacrylate) (PLMA) – P(PEOnMEMA) and amphiphilic anionic blockcopolymers PLMA – PMAA were prepared by the RAFT method, and their properties in aqueous and THF... [to full text]

The main goal of this work was to synthesize polyelectrolyte brushes containing poly(ethylene oxide) side chains by living polymerization. Brush-like macromolecules are unique polymer molecules whose conformation and physical properties are controlled by steric repulsion of densely grafted side chains. Molecules can be either flexible or stiff, depending on the grafting density and the length of the side chains. Polymerization of macromonomers is one of the most useful ways to prepare brush copolymers. However, with the macromonomer method, the distribution of the spacing of the side chains cannot be entirely controlled which along with broad and multimodal molecular weight distribution makes these polymers heterogeneous. These problems were considered to be overcome with the use of controlled/living polymerization. Conventional free-radical and RAFT copolymerization of poly(ethylene oxide) substituent containing methacrylate macromonomers, PEO5MEMA and PEO45MEMA, with methacrylic acid (MAA) was studied by the use of 1H NMR spectroscopy for an analysis of residual monomers. RAFT copolymerization of PEO45MEMA and MAA enabled to synthesize comb copolymers with low composition distribution and more homogeneous distribution of PEO side chains along the mainchain. Amphiphilic non-ionic blockcopolymers poly(lauryl methacrylate) (PLMA) – P(PEOnMEMA) and amphiphilic anionic blockcopolymers PLMA – PMAA were prepared by the RAFT method, and their properties in aqueous and THF... [to full text] / Vienas iš šiuolaikinės polimerų chemijos uždavinių – gauti numatytos molekulinės masės ir architektūros polimerines medžiagas. Neseniai buvo sukurti nauji radikalinės polimerizacijos metodai, kurie priskiriami gyvybingajai (valdomai) polimerizacijai (GRP). Makromonomerų (MM) gyvybingoji radikalinė polimerizacija yra efektyvus būdas gauti šepetinius (cilindrinius) polimerus). Šepetiniai polimerai – tai makromolekulės, kuriose prie pagrindinės polimerinės grandinės prijungta daug šoninių mažesnės molekulinės masės polimerinių (oligomerinių) grandinių. Dėl tarp šoninių grandinių esančių erdvinės stūmos jėgų tokios makromolekulės įgauna neįprastų savybių, pvz., standumą, cilindrinę formą, didelį segmentų tankį. Pagrindinis šio darbo tikslas buvo susintetinti norimos sudėties šepetinius polielektrolitinius polimerus, sudarytus iš krūvį turinčios poli(met)akrilato pagrindinės grandinės ir šoninių polietilenoksido grandinių, ir ištirti jų savybes. Svarbiausieji šio darbo rezultatai, atspindintys jo naujumą, originalumą ir svarbą: Pirmą kartą nuodugniai ištirta metakrilo rūgšties (MAR) ir dviejų skirtingų molekulinių masių polietilenoksido metakrilatų PEOnMEMA (n = 5, 45) kopolimerizacija įprastiniu radikaliniu ir RAFT metodais. Sukurta metodika PEO makromonomerų kopolimerizacijos kinetikai tirti, užrašant 1H BMR spektrus in situ ir įvertinant likutinę monomerų koncentraciją reakcijos mišinyje bei momentinę kopolimero sudėtį iki gilių konversijų. Netiesiniu kintamųjų paklaidų metodu... [toliau žr. visą tekstą]

In this thesis methodological developments have been made for the description of flexible conjugated dyes in room temperature spectrum calculations. The methods in question target increased accuracy and efficiency by combining classical molecular dynamics (MD) simulations with time-dependent response theory spectrum calculations. For absorption and fluorescence spectroscopies a form of conformational averaging is used, where the final spectrum is obtained as an average of spectra calculated for geometries extracted from ground and excited state MD simulations. For infrared and Raman spectroscopies averaged spectra are calculated based on individual spectra, obtained for zero-temperature optimized molecular structures, weighted by conformational statistics from MD trajectories. Statistics for structural properties are also used in both cases to gain additional information about the systems, allowing more efficient utilization of computational resources. As it is essential that the molecular mechanics description of the system is highly accurate for methods of this nature to be effective, high quality force field parameters have been derived, describing the molecules of interest in either the MM3 or CHARMM force fields. These methods have been employed in the study of three systems. The first is a platinum(II) actylide chromophore used in optical power limiting materials, for which a ultraviolet/visible absorption spectrum has been calculated. The second is a family of molecular probes called luminescent conjugated oligothiophenes, used to detect and characterize amyloid proteins, for which both absorption and fluorescence spectra have been calculated. Finally, infrared and Raman spectra have been calculated for a group of branched oligothiophenes used in organic solar cells. In addition, solvation effects have been studied for conjugated poly\-eletrolytes in water, resulting in the development of two solvation models suitable for this class of molecules. The first uses a quantum meachanics/molecular mechanics (QM/MM) description, in which the solute mole\-cule is described using accurate quantum mechanical methods while the surrounding water molecules are described using point charges and polarizable point dipoles. The second discards the water entirely and removes the ionic groups of the solute. The QM/MM model provides highly accurate results while the cut-down model gives results of slightly lower quality but at a much reduced computational cost. Finally, a study of protein-dye interactions has been performed, with the goal of explaining changes in the luminescence properties of the LCO chromophores when in the presence of amyloid proteins. Results were less than conclusive.

Polymer electrolyte membrane fuel cells (PEMFCs) have been looked as potential alternative energy conversion devices to conventional energy conversion systems such as combustion engines. Proton conducting membranes (PEMs) are one critical component of PEMFCs. The development of novel electrolyte membranes with dense structure, good mechanical flexibility, and high proton conductivity, but with little or no dependence on humidity at temperatures above 100¡ãC remains an important challenge to the realization of practical PEM fuel cells. In this thesis, to solve the technical difficulties existing in current high temperature PEM systems based on phosphoric acid and imidazole, a new type of proton conducting species 1H-1,2,3-triazole has been explored, and proved to have high proton conductivity and also enough electrochemical stability for fuel cell applications. In further experiments, effective methods have been developed to synthesize triazole derivatives and polymers. The properties of the synthesized polymers have studied and reported in this thesis. Preliminary computational simulations have also been performed to study the proton conducting mechanism to provide intrinsic information of the proton conducting process in 1H-1,2,3-triazole. In the final part, research works on other proton conducting species including H3PO4 and other heterocycles have been reported.