Filmes de benzotriazol (BTAH) formados sobre aços carbono e inoxidável 316L foram estudados em meios de ácido sulfúrico, ácido clorídrico e cloreto de sódio a 25°C. Os seguintes aspectos foram considerados: as condições de formação do filme, sua eficiência, sua resistência em meios não contendo o inibidor,a presença de aditivos e o efeito do transporte de massa sobre o mecanismo da reação. Foram empregadas como técnicas: transitórios de potencial de circuito aberto, ensaios gravimétricos, curvas de polarização potenciostáticas e potenciodinâmicas com eletrodo parado e de disco rotativo, cronoamperometria, espectroscopia de impedância eletroquímica, microscopia ótica, microscopia eletrônica de varredura e análise da superfície por dispersão de energia. O BTAH se mostrou inibidor na grande maioria dos meios para os dois materiais estudados. A resistência dos filmes formados não existe ou é parcial quando as superfícies metálicas revestidas com o filme são imersas nos meios estudados sem inibidor. A adição de Cu(II) aumenta a resistência dos filmes, para determinadas relações [BTAH]/[Cu(II)] que estabilizem o intermediário Cu(I). A presença de íons provenientes da dissolução do aço inoxidável 304 em H2SO4 0,50 mol.L-1 contendo BTAH, eleva significativamente a resistência dos filmes formados, quando estes são expostos aos meios sem inibidor. O cloreto de trimetildodecil amônio exerce sinergismo sobre a ação do BTAH como inibidor de corrosão do aço carbono 1010 em meios ácidos. Superfícies de aço carbono previamente reduzidas são mais eficientes na formação de filmes resistentes aos meios sem inibidor. O transporte de massa do BTAH é uma etapa cinética importante no mecanismo de formação do filme sobre aço inoxidável 316L em meio de HCI 2,0 mol.L-1. O BTAH se mostrou inibidor para a corrosão do aço quando revestido pelo \"primer\" da tinta epóxi, quando adicionado à tinta ou quando o filme é formado antes da aplicação do \"primer\". / Benzotriazole (BTAH) films formed on carbon steel and 316L stainless steel have been studied in sulfuric and chloridric acids and in sodium choride solutionsat 25°C. Different aspects were considered: the film formation conditions, its efficiency, its resistance, the presence of additives and the effect of mass transport on the reaction mechanism. Open circuit potential measurements, weight loss experiments, potenciostatic and potentiadynamic polarization curves using stationary and rotating disc electrode, chronoamperometry, electrochemical impedance spectroscopy, optical and scanning electron microscopies and energy dispersive surface analysis have been used as techniques. BTAH have shown inhibitive effect over the majority of the systems studied. The film resistance depends on the presence of the inhibitor in the solution but the result is different if the film is formed in solution containing additives as copper (II) ions or cations obtained from 304 SS dissolution in H2SO4 media; in this case the films resist to chloridric acid media without BTAH. Dodecyltrimetilammonium chloride presents synergism on the inhibitive BTAH action forcarbon steel in acid solution. The BTAH mass transport represents an important step on the film formation mechanism. BTAH is also an effective inhibitor for carbon steel covered by epoxy primer when it is added to the primer or when the film is formed on the carbon steel surface from a H2SO4 solution containing BTAH.

Design of a monomer is a viable route for adjusting the properties of its corresponding polymer. The main goal of this study is to design and synthesize novel soluble polymers having various colors of color palette and amenable for use in electrochromic device applications. In designing the monomers, the factors affecting the properties of the polymers are also considered. For this purpose, each part of the monomers is chosen properly for each desirable properties and the effect of them is investigated separetely. Thus, this study is based on the investigation of the effect of three major parts on the polymer properties: Donor groups, acceptor groups and the length of alkyl chain. For this aim, nine D-A-D type monomers, TSeT, ESeE, PSeP-C10, PSP-C10, PNP-C10, POP-C10, PSeP-C4, PSP-C4 and PSP-C6, and their corresponding polymers, P(TSeT), P(ESeE), P(PSeP-C10), P(PSP-C10), P(PNP-C10), P(POP-C10), P(PSeP-C4), P(PSP-C4) and P(PSP-C6), based on thiophene, 3,4-ethylenedioxythiophene (EDOT), and 3,3-dialkyl-3,4-dihydro-2H-thieno[3,4-b]-[1,4]dioxepine (ProDOT-Cn) as D units and 2,1,3-benzoselenadiazole, 2,1,3-benzothiadiazole, 2-decyl-2H-benzo[d][1,2,3]triazole, and 2,1,3-benzooxadiazole as A units were synthesized. The obtained polymers have somewhat low band gap between 1.13 eV and 1.80 eV, they show electrochromic behaviors. Among them P(POP-C10), P(PSP-C10) and P(PSP-C6) have cyan color which is one leg of CMY (Cyan-Magenta-Yellow) color spaces. Since there have been scant studies on cyan colored polymers in the literature, these polymers are so precious. Via copolymerization of PNP-C10 and PSeP-C10, the first electrochemically synthesized neutral state black polymer was obtained.

The synthesis and preliminary optoelectronic properties of a series of donor-acceptor (DA) type polymers differing by the acceptor units in the polymer backbone were investigated. Polymers CoP1, CoP2 and CoP3 were designed to yield alternating DA segments with randomly distributed different acceptor units along polymer backbone. The combination of neutral state red colored and neutral state green colored materials resulted in different neutral state colors with respect to their additional acceptor unit. 5,8-Dibromo-2,3-bis(4-tert-butylphenyl) quinoxaline, 5,8-dibromo-2,3-di(thiophen-2-yl)quinoxaline and 4,7-dibromobenzo[c][1,2,5]selenadiazole units were perceived as additional acceptor units and these constituents were combined with the 4,7-dibromo-2-dodecyl-2H-benzo[d][1,2,3]triazole unit and the 2,5-bis(tributylstannyl)thiophene moiety via Stille coupling. The resultant donor acceptor type random copolymers indicated that possessing 5,8-dibromo-2,3-di(thiophen-2-yl)quinoxaline as an extra electron deficient with 4,7-dibromo-2-dodecyl-2H-benzo[d][1,2,3]triazole unit on the same polymer backbone originated a neutral state black colored copolymer along with spanning the entire visible spectrum.

Filmes de benzotriazol (BTAH) formados sobre aços carbono e inoxidável 316L foram estudados em meios de ácido sulfúrico, ácido clorídrico e cloreto de sódio a 25°C. Os seguintes aspectos foram considerados: as condições de formação do filme, sua eficiência, sua resistência em meios não contendo o inibidor,a presença de aditivos e o efeito do transporte de massa sobre o mecanismo da reação. Foram empregadas como técnicas: transitórios de potencial de circuito aberto, ensaios gravimétricos, curvas de polarização potenciostáticas e potenciodinâmicas com eletrodo parado e de disco rotativo, cronoamperometria, espectroscopia de impedância eletroquímica, microscopia ótica, microscopia eletrônica de varredura e análise da superfície por dispersão de energia. O BTAH se mostrou inibidor na grande maioria dos meios para os dois materiais estudados. A resistência dos filmes formados não existe ou é parcial quando as superfícies metálicas revestidas com o filme são imersas nos meios estudados sem inibidor. A adição de Cu(II) aumenta a resistência dos filmes, para determinadas relações [BTAH]/[Cu(II)] que estabilizem o intermediário Cu(I). A presença de íons provenientes da dissolução do aço inoxidável 304 em H2SO4 0,50 mol.L-1 contendo BTAH, eleva significativamente a resistência dos filmes formados, quando estes são expostos aos meios sem inibidor. O cloreto de trimetildodecil amônio exerce sinergismo sobre a ação do BTAH como inibidor de corrosão do aço carbono 1010 em meios ácidos. Superfícies de aço carbono previamente reduzidas são mais eficientes na formação de filmes resistentes aos meios sem inibidor. O transporte de massa do BTAH é uma etapa cinética importante no mecanismo de formação do filme sobre aço inoxidável 316L em meio de HCI 2,0 mol.L-1. O BTAH se mostrou inibidor para a corrosão do aço quando revestido pelo \"primer\" da tinta epóxi, quando adicionado à tinta ou quando o filme é formado antes da aplicação do \"primer\". / Benzotriazole (BTAH) films formed on carbon steel and 316L stainless steel have been studied in sulfuric and chloridric acids and in sodium choride solutionsat 25°C. Different aspects were considered: the film formation conditions, its efficiency, its resistance, the presence of additives and the effect of mass transport on the reaction mechanism. Open circuit potential measurements, weight loss experiments, potenciostatic and potentiadynamic polarization curves using stationary and rotating disc electrode, chronoamperometry, electrochemical impedance spectroscopy, optical and scanning electron microscopies and energy dispersive surface analysis have been used as techniques. BTAH have shown inhibitive effect over the majority of the systems studied. The film resistance depends on the presence of the inhibitor in the solution but the result is different if the film is formed in solution containing additives as copper (II) ions or cations obtained from 304 SS dissolution in H2SO4 media; in this case the films resist to chloridric acid media without BTAH. Dodecyltrimetilammonium chloride presents synergism on the inhibitive BTAH action forcarbon steel in acid solution. The BTAH mass transport represents an important step on the film formation mechanism. BTAH is also an effective inhibitor for carbon steel covered by epoxy primer when it is added to the primer or when the film is formed on the carbon steel surface from a H2SO4 solution containing BTAH.

Foi realizado o estudo do sinergismo álcool - benzotriazol como inibidores de oxidação para o aço carbono 1008 em meio de H2SO4 0,5 mol/L-1. Foram utilizados os álcoois metanol, etanol e propanol em frações molares iguais a 0,008. Utilizaram-se como técnicas para o estudo eletroquímico das interfaces: medidas de potencial de circuito aberto em função do tempo, ensaios gravimétricos, curvas de polarização potenciostática anódica e catódica e espectroscopia de impedância eletroquímica. A caracterização da superfície e a análise dos produtos de corrosão foi feita por microscopia óptica; microscopia eletrônica de varredura e espectrometria por dispersão de energia. Os resultados mostraram que a corrosão é generalizada para o aço carbono 1008 em todos meios estudados. O efeito sinérgico álcool BTAH, foi verificado em todos os meios contendo álcool - BTAH 1,0.10-3 mol/L-1. O benzotriazol se comporta como um inibidor catódico e anódico sobre o aço carbono em todos os meios estudados. Estudos de polarização mostraram que na região de Tafel da reação H+/H2 o filme inibidor em meio de BTAH e da mistura etanol - BTAH obedece à isoterma de adsorção de Langmuir. Ensaios por microscopia eletrônica de varredura seguidas de EDS mostraram que as inclusões após ataque em meio de H2SO4 0,5 mol/L-1 + BTAH 1.0.10-2 mol/L-1 + etanol são totalmente dissolvidas, justificando a eficiência máxima inferior a 100%. / The synergic effect of mixtures of alcohol - benzotriazole as corrosion inhibitors for the 1008 carbon steel in 0.5 mol.L-1 H2SO4 medium was studied. Methanol, ethanol and propanol were used in molar fractions equal to 0.008. The techniques used for the electrochemical study of the interfaces were: open circuit potential measurements, weight loss experiments, anodic and cathodic potentiostatic polarization curves and electrochemical impedance spectroscopy; the surface characterization and the corrosion product analysis were performed by optical microscopy, scanning electron microscopy - SEM and energy dispersive spectroscopy - EDS. The results showed the occurrence of generalized corrosion on 1008 carbon steel surfaces in all the studied media. The synergic effect of alcohol / BTAH was observed in all the media containing 1.0.10-3 mol.L-1 BTAH. Benzotriazol acts as a cathodic and anodic inhibitor on 1008 carbon steel in all the studied media. Polarization studies showed that the inhibitor film follows the Langmuir isotherm in the presence of BTAH and ethanol-BTAH, in the Tafel region correspondent to the H+/H2 reaction. Scanning electron microscopy and energy dispersive measurements revealed total dissolution of the inclusions after surface attack in 0.5 mol.L-1 H2SO4 + 1.0.10-2 mol.L-1 BTAH + ethanol medium, justifying the maximum efficiency lower than 100 %.

Foi estudado o comportamento eletroquímico de interfases Cu/H2SO4 0,5 mol L-1 na ausência e presença de compostos triazólicos - benzotriazol (BTAH) e tolitriazol (TTAH) e de surfactantes: dodecilsulfato de sódio (SDS aniônico) e cloreto de dodecilamônio (DAC catiônico) a 25ºC, empregando eletrodo parado e de disco rotativo (EDR). Foram empregadas como técnicas medidas de potencial de circuito aberto, polarização potenciostática e potenciodinâmica, cronoamperometria, espectroscopia de impedância eletroquímica e microscopia óptica. As características inibidoras do filme formado dependem da natureza dos aditivos e das condições hidrodinâmicas. As interfases contendo BTAH, TTAH, BTAH + TTAH, BTAH + SDS e TTAH + SDS apresentaram uma faixa ampla de potencial em que o cobre se mostrou passivado, chegando a 200 mV para a mistura BTAH + SDS empregando EDR. Densidades de corrente de passivação tão baixas quanto 2µA cm-2 foram observadas com EDR na presença de BTAH + TTAH. As misturas composto triazólico - surfactante mostraram filmes menos resistentes. Os surfactantes isolados não produzem faixa passiva e antecipam o potencial de oxidação do cobre com eletrodo parado. As misturas triazol - DAC só produzem faixa passiva com EDR. Todos os aditivos se mostraram inibidores para a reação H+/H2, destacando-se, com eletrodo parado, BTAH, TTAH e BTAH + TTAH. / The electrochemical behavior of 0.5 mol.L-1 Cu/H2SO4 interphases has been studied in the presence and in the absence of triazolic compounds-benzotriazole (BTAH) and tolitriazole (TTAH) and of surfactants - sodium dodecylsulphate (anionic, SDS) and dodecylammonium chloride (cationic, DAC) at 25ºC, using non-stirred electrode and rotating disc electrode (RDE). Open circuit potential, potentiostatic and potenctiodinamic polarization, chronoamperometry, electrochemical impedance spectroscopy, and optical microscopy were used as techniques. The inhibitive features of the formed film depend on both the nature of the additives and on the hydrodynamic conditions. The interphases containing BTAH, TTAH, BTAH + TTAH, BTAH + SDS e TTAH + SDS presented a wide potential range where the copper is passivated, reaching to 200 mV for BTAH + SDS mixture using RDE. Low passivating current densities (2µA cm-2) were observed with RDE in the presence of BTAH + TTAH. Triazolic compound?surfactant mixtures have originated less resistant films. Isolated surfactants do not originate passive ranges and anticipate the oxidation potential of copper under non stationary conditions. The mixtures triazole-DAC only produce passive range at stationary conditions. All the additives have shown to be inhibitors for the H+/H2 reaction, specially BTAH, TTAH e BTAH + TTAH using non stirred conditions.

A new class of &pi / -conjugated monomers was synthesized with combination of electron donating and electron-withdrawing heterocyclics to understand the effects of structural differences on electrochemical and optoelectronic properties of the resulting polymers. Electron deficient benzotriazole, substititued with benzyl from two available sites, coupled with stannylated electron donating groups, ethylenedioxythiophene (EDOT) and thiophene (Th), to yield four different monomers / 1-benzyl-4,7-di(thiophen-2-yl))-2H-benzo[d][1,2,3] triazole (BBTA), 2-benzyl-4,7-di(thiophen-2-yl))-2H-benzo[d][1,2,3] triazole (BBTS), 1-benzyl-4,7-bis(2,3-dihydrothieno[3,4-b]dioxin-5-yl)-2H-benzo [d][1,2,3]triazole (BBTEA), 2-benzyl-4,7-bis(2,3-dihydrothieno[3,4-b]dioxin-5-yl)-2H-benzo [d][1,2,3]triazole (BBTES). Furthermore, EDOT and thiophene terminated napthalene-2,3-crown ether containing monomers, 14,19-di(thiophen-2-yl)-naphtho[2,3-b][1,4,7,10,13] pentaoxacyclo pentadecane (TNCT), 14,19-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-naphtho[2,3-b][1,4,7,10,13]pentaoxacyclopenta decane (ENCE), were synthesized to observe the effect crown ether moiety on the final electrochemical and optoelectronic properties of resultant polymers. Cyclic voltammetry, UV-Vis-NIR spectroscopy and colorimetry techniques were employed to examine electrochemical and optoelectronic properties of all monomers and polymers. Experimental results showed that alteration of substituent, substitution position and donor groups&rsquo / strength lead to obtain polymers with different redox behaviors, optical band gaps and different number of achievable colored states.

Foi realizado o estudo do sinergismo álcool - benzotriazol como inibidores de oxidação para o aço carbono 1008 em meio de H2SO4 0,5 mol/L-1. Foram utilizados os álcoois metanol, etanol e propanol em frações molares iguais a 0,008. Utilizaram-se como técnicas para o estudo eletroquímico das interfaces: medidas de potencial de circuito aberto em função do tempo, ensaios gravimétricos, curvas de polarização potenciostática anódica e catódica e espectroscopia de impedância eletroquímica. A caracterização da superfície e a análise dos produtos de corrosão foi feita por microscopia óptica; microscopia eletrônica de varredura e espectrometria por dispersão de energia. Os resultados mostraram que a corrosão é generalizada para o aço carbono 1008 em todos meios estudados. O efeito sinérgico álcool BTAH, foi verificado em todos os meios contendo álcool - BTAH 1,0.10-3 mol/L-1. O benzotriazol se comporta como um inibidor catódico e anódico sobre o aço carbono em todos os meios estudados. Estudos de polarização mostraram que na região de Tafel da reação H+/H2 o filme inibidor em meio de BTAH e da mistura etanol - BTAH obedece à isoterma de adsorção de Langmuir. Ensaios por microscopia eletrônica de varredura seguidas de EDS mostraram que as inclusões após ataque em meio de H2SO4 0,5 mol/L-1 + BTAH 1.0.10-2 mol/L-1 + etanol são totalmente dissolvidas, justificando a eficiência máxima inferior a 100%. / The synergic effect of mixtures of alcohol - benzotriazole as corrosion inhibitors for the 1008 carbon steel in 0.5 mol.L-1 H2SO4 medium was studied. Methanol, ethanol and propanol were used in molar fractions equal to 0.008. The techniques used for the electrochemical study of the interfaces were: open circuit potential measurements, weight loss experiments, anodic and cathodic potentiostatic polarization curves and electrochemical impedance spectroscopy; the surface characterization and the corrosion product analysis were performed by optical microscopy, scanning electron microscopy - SEM and energy dispersive spectroscopy - EDS. The results showed the occurrence of generalized corrosion on 1008 carbon steel surfaces in all the studied media. The synergic effect of alcohol / BTAH was observed in all the media containing 1.0.10-3 mol.L-1 BTAH. Benzotriazol acts as a cathodic and anodic inhibitor on 1008 carbon steel in all the studied media. Polarization studies showed that the inhibitor film follows the Langmuir isotherm in the presence of BTAH and ethanol-BTAH, in the Tafel region correspondent to the H+/H2 reaction. Scanning electron microscopy and energy dispersive measurements revealed total dissolution of the inclusions after surface attack in 0.5 mol.L-1 H2SO4 + 1.0.10-2 mol.L-1 BTAH + ethanol medium, justifying the maximum efficiency lower than 100 %.

The present thesis entitled “Design, Synthesis and Characterization of Novel Nanomaterials” is divided into five chapters, staring with a general introduction. The remaining chapters focus on four different areas/projects that I have worked on. Chapter 1: Introduction to nanomaterials This chapter reviews the basic concepts of nanomaterials and their fabrication methods. Nanomaterials are defined as materials whose dimensions (at least one) are below 100 nm. One of the most exciting aspects of nanomaterials is that their properties may differ significantly from those of the corresponding bulk materials. Nanomaterials fabrication methods can be broadly classified according to whether the assembly follows either i) the bottom-up approach or ii) the top-down approach. These methods have been discussed with various examples including the self-assembly of proteins, peptides and small molecules. In the top-down approach synthetic procedures for Graphene Oxide and its application are discussed. All characterization techniques that are used for characterizing the nanomaterials are also described briefly. Chapter 2 Section A: Self-assembly of 1-Hydroxy benzotriazole (HOBT) in water The studies presented in Chapter 2 identifies HOBT as the smallest non-peptide building block that spontaneously self-assembles into hollow micro tubular structures upon evaporation of water. The tubes form under ambient conditions by rolling over of crystalline sheets of HOBT. The packing of HOBT in the tubes seem to be predominantly driven by intermolecular π-stacking interactions between the aromatic rings of HOBT. These structural and packing patterns are similar to those found in nanotubes formed by the self-assembly of peptides and other larger molecules. The cavities of these thermolabile microtubes act as molds for casting gold nanoparticles for the synthesis of gold microrods with monodisperse dimensions. The non-reacting inner surfaces of the cavities have been used to uniquely synthesize R6G-functionalized gold microrods. With these features, HOBT is an important novel non-peptide building block for accessing micro and nanometric materials for their applications in medicine, biology and molecular biotechnology. Section B: Controlling the orientation of self-assembly of HOBT microtubes The studies presented in this chapter address the self-assembly of HOBT into microtubular structures in different solvents of varying polarities (H2O and DCM:MeOH) to understand the role of solvent volatility and its direction on the orientation of the HOBT microtubes. HOBT self-assembles from DCM:MeOH mixtures in its bipolar canonical form and is coordinated with its water of hydration, similar to its crystals obtained from water. FTIR and TGA data shows that MeOH is also integrated with the microtubes. We observe for the first time that the orientation of microtubular self-assembly is controlled in the direction of evaporation of the solvent. We demonstrate further this feature by controlling the orientation of HOBT self-assembly in exclusively vertical direction through controlled vertical evaporation of the solvent mixture DCM:MeOH (9:1). Additionally, the unique transition between vertical and horizontal orientations for self-assembled HOBT microtubes is achieved by simple change of solvation between aqueous and organic solvents. These results reveal a dynamic relationship between the rate of evaporation of solvent and the rates of formation of different self-assembled morphologies. The rate of evaporation of the solvent primarily governs the rate of formation of the tubes, rather than their orientations in three dimensions. Chapter 3: Chemical origins of debris in Graphene Oxide (GO) This chapter is focused on the investigation of the carbonyl rich fragments arising from GO and provides an understanding of its formation. The fragments are expelled from GO due to an uncontrolled nucleophile driven reaction in aqueous medium leaving the holes on the sheet. These fragments are carbonyl rich small (5 ± 2 nm) nonaromatic molecules that form as by-products of oxidative chemical reactions that occur at the sp3 clusters on the basal surface of GO sheets when they are treated with nucleophilic bases under aqueous conditions. The structure and size of the debris, and hence that of the hole, depend on the size of the sp3 cluster on the sheet. These debris fall out of the GO sheet surface, leading to formation of nanometer sized holes. Formation of debris and hence the holes can be avoided by using anhydrous polar solvents. This work sheds new light on the fundamental structure of GO and the prevention of debris from it during redox reactions enabling better control over functionalization of the GO surface. Chapter 4: Measurement of mechanical properties of polypeptide fragment from Insulin like growth factor binding protein nanotubes by the Peak Force QNM method This chapter describes the discovery of Polypeptide fragment from an IGFBP-2. This fragment self-assembles spontaneously and reversibly into nanotubular structures under oxidizing conditions. These nanotubes were characterized by using Transmission electron microscopy. Notably as compared to the monomer, an increase in intrinsic fluorescence upon self-assembly. The thermal stability of these nanotubes is realized form the fluorescence studies. Peak Force Quantitative Nanomechanical Mapping method of AFM was used to measure the Young’s modulus of the nanotubes. These nanotubes were found to have Young’s modulus value of ~10 Gpa, which is comparable to those of bones presumably due to intermolecular disulphide bonds. These nanotubes will have potential applications in tissue engineering. Chapter 5: Probing the pathways of n→π* interaction in peptides This chapter deals with the theoretical study of n→π* interaction in designed peptidomimetics. The n→π* interaction involves the delocalization of the lone pair of the donor group into the antibonding orbital (π*) of a carbonyl group. However despite beeing extensively studied there exists a debate over the validation of these n→π* interaction which is reminiscent to Bürgi and Dunitz trajectory. This chapter present our findings that peptidomimetics containing the 5,6-dihydro-4H-1,3-oxazine (Oxa) and 5,6-dihydro-4H-1,3-thiazine (Thi) functional groups at the C-terminus of Pro selectively stabilizes the cis conformer by reverse n→πi-1* interaction. These systems have been used to study the n→πi1* interaction using Natural Bond Orbital (NBO) method. Our study reveals that the energetically most favorable trajectory of a nucleophile for a favorable n→π* interaction presumably to facilitate the overlap between the lonepair of the nucleophile and the antibonding orbital of the carbonyl group. The geometrical requirements for the optimum n→π* interaction depends on the relative orientations of the orbitals that are involved. This study has implications for more accurately identifying long distant n→π* interaction.

One of the main challenges to transform highly useful Direct Methanol Fuel Cells (DMFC) into a commercially viable technology has been to develop a low cost polymer electrolyte membrane (PEM) with high proton conductivity, high stability and low methanol crossover under operating conditions desirably including high temperatures. Nafion, the widely used PEM, fails to meet all of these criteria simultaneously. Recently developed acid-base polymer blend membranes constitute a promising class of PEMs alternative to Nafion on above criteria. Even though some of these membranes produce better performance than Nafion, they still present numerous opportunities for maximizing high temperature proton conductivity and dimensional stability with concomitant minimization of methanol crossover. Our contribution embarks on the fundamental study of one such novel class of blend membranes viz., sulfonated poly (ether ether ketone) (SPEEK)(95 % by weight) blended with polysulfone tethered with base (5 % by weight) such as 2-aminobenzimidazole (ABIm), 5-amino-benzotriazole (BTraz) and 1H-perimidine (PImd), developed by Manthiram group at The University of Texas at Austin. In this work, we report extensive all-atom classical as well as ab-initio molecular dynamics (MD) simulations of such water-methanol solvated blend membranes (as well as pure SPEEK and Nafion) the first time. Our approach consists of three steps: (1) Predict dynamical properties such as diffusivities of water, methanol and proton in such membranes (2) Validate against experiments (3) Develop understanding on the interplay between basic chemistry, structure and properties, the knowledge that can potentially be used to develop better candidate membranes. In particular, we elucidate the impact of simple, fundamental physiochemical features of the polymeric membranes such as hydrophilicity, hydrophobicity, structure or the size of the base on the structural manifestations on the bigger scale such as nanophase segregation, hydrogen bonding or pore sizes, which ultimately affect the permeant transport through such systems. / text