Nous étudions la structure des solutions concentrées de polyélectrolytes (PE). Celle-ci n'a fait l'objet que de rares études expérimentales et aucun ordre d'orientation n'a jamais pu être observé dans les solutions de PE flexibles et semi-flexibles, bien que des travaux théoriques, basés sur l'approche d'Onsager, prévoient l'apparition d'une phase nématique aux fortes concentrations. Nous avons mesuré la position q* dans l'espace réciproque du pic présent dans la fonction de corrélation des solutions de PE fortement chargés obtenue par diffusion de rayonnement (DXPA et DNPA), et avons confronté sa variation avec la concentration c aux lois d'échelles théoriques q*~ca. Nous avons combiné des très fortes concentrations avec une haute résolution spatiale. La rigidité intrinsèque du PE est le paramètre clef de l'étude. En effet, le PSS, PE flexible, présente 3 régimes déjà connus : a=1/2 -régime semi-dilué- a=1/4 -régime concentré- un régime " ionomère " aux plus fortes concentrations pour lequel a=0. Le PDADMAC, PE semi-flexible, présente un comportement plus original puisque 4 régimes se succèdent : régimes semi-dilué et concentré avec a=1/2 et 1/4, puis deux régimes pour lesquels a=1 puis 1/2 qui sont totalement inédits. Le PaMSS, de rigidité intrinsèque intermédiaire, présente un comportement ambivalent, puisque les régimes semi-dilué et concentré précèdent un régime où a=1, puis un comportement " ionomère ". Nous introduisons un modèle simple permettant d'interpréter la succession des régimes a=1 puis 1/2 par l'apparition d'un ordre d'orientation. Nous discutons aussi les différences observées par DXPA et DNPA, et le rôle de la force ionique, variée par ajout de sel.

Per- and polyfluoroalkyl substances (PFASs) are a group of toxic and persistent organic compounds. Their properties make them extremely resistant and they have been shown to have bioaccumulation and toxic properties in the environment and also to biomagnify in both aquatic and terrestrial food webs. This study has analysed different PFASs in African Darter (Anhinga rufa) eggs from five sites along Vaal River; Orange River, South Africa. Sixteen of 23 analysed PFASs were detected and quantified, and the homologue profiles were studied from all five sites. Total perfluorooctane sulfonic acid (PFOS) (all structural isomers) was the predominated compound of all PFASs, accounting for 88-98% for all sites, with a median concentration range of 58 ng/g ww to 2473 ng/g ww. The second highest concentration was found for perfluorodecanoic acid (PFDA) (1.9-42 ng/g ww), followed by perfluorononanoic acid (PFNA) (1.1-14 ng/g ww) and perfluorohexane sulfonate (PFHxS) (0.68-6.0 ng/g ww). The results showed significantly that the three up-stream sites (Welverdiend, Schoemansdrift and Orkney East) had similar patterns and that eggs from Schoemansdrift had the highest levels of PFASs. This may indicate the same source of origin for these three sites and that Schoemansdrift are closest to the contamination source. The three sites (Welverdiend, Schoemansdrift and Orkney East) with similar pattern is closest to Gauteng, which can be where the emission source is located, because it is an industrial area. Perfluoroalkyl carboxylic acids (PFCAs) and PFOS might originate from different sources and the source for PFCAs could be degradation of fluorotelomer-based precursors. Structural isomer profiles of PFOS showed similar results as the PFAS homologue patterns, which give further indication of the source of origin. The contribution of linear PFOS (L-PFOS) to the total amount of PFOS was between the range of 94 and 97%. Bloemhof had the highest concentration of branched isomers among all sites. The L-PFOS concentrations in Bloemhof were also significantly differ from Schoemansdrift. This indicate two different sources between Bloemhof and the three up-steam sites, or an effect of environmental fractionation.

The main motivation of this thesis is derived from the fact that physics of disordered systems like conjugated polymer has yet not achieved as concrete understanding as ordered and crystalline systems such as inorganic semiconductors. Through the work done in this thesis, several efforts have been made in order to understand basic charge transport (hopping, current injection) phenomena and photo-physical properties (photoluminescence quenching, absorption, photoconductivity) in conjugated polymer and their hybrid composites. The thesis consists of 7 chapters. Chapter 1 discusses the background knowledge and information of the general properties of conjugated polymers, quantum dots and their hybrid nanocomposites. Chapter 2 deals with the sample preparation and experimental techniques used in this thesis. Chapter 3 elaborates the temperature and field dependent anisotropic charge transport in polypyrrole. Chapter 4 presents an idea to probe and correlate disorder and transport properties using impedance and Raman spectroscopy. Chapter 5 mainly talks about the doping level dependent photophysical and electrical properties of poly(3-hexylthiophene). Chapter 6 reveals the charge transport phenomena in hybrid composites of poly(3,4-ethyldioxythiophene):polysterene sulfonate (PEDOT:PSS) and cadmium telluride quantum dots. Chapter 1: Conjugated polymers and their hybrid systems are easily processible and cost effective material having huge scope for advanced materials of the future. Although variable range hopping (VRH) is widely accepted to model charge transport in π-conjugated systems, but at very low temperatures, high fields, high carrier concentrations one need to explore other models. Conjugated polymers are anisotropic intrinsically. Therefore, anisotropic charge transport can provide basic insights about the physics of charge hopping. Quantum dots, and their hybrid nanocomposites with semiconducting polymers receiving a huge attention for light emission and photovoltaic purposes. It is important to learn about the charge injection,barrier heights, etc. in order to achieve efficient hybrid devices. Chapter 2: Synthesis of the samples, both conjugated polymers and quantum dots, and fabrication of hybrid devices is an important and integral part of this thesis. An Electropolymerization technique is used for making polymer samples on conducting substrates. This is quite interesting because one can tune doping level, disorder and thickness simultaneously. Hydrothermal process is adopted to get highly aqua-dispersible quantum dots. Samples are characterized by different techniques like Raman spectroscopy, energy dispersive spectroscopy. Photoluminescence, UV-Vis absorption, transmission electron microscopy and atomic force microscopy are used to explore several properties of the polymer and hybrid nanocomposites. Chapter 3: It is known that conjugated polymers are intrinsically one–dimensional materials. Therefore it is important to learn anisotropic behavior of these complex systems. Hence, a comparison of electronic transport to their morphology has been carried out and role of carrier density and disorder is discussed further. Both in-plane and out-of-plane charge transport is studied in electrochemically deposited polypyrrole on platinum. Strong anisotropy is observed in the system which is correlated to granular morphology. Field dependence of anisotropic conductivity is also explored. Field scaling analysis shows that all field dependent curves of conductance at different temperatures can fall on to single master curve. Glazman – Matveev model is used to describe nonlinear conduction in field dependence and nonlinearity exponent is estimated. Disorder and carrier density along with the morphological structure like length and orientation of polymer chains with stacking arrangement of different layers in PPy films play an important role in governing the anisotropy in transport properties. Chapter 4: Two different techniques, namely impedance and Raman spectroscopies are used to probe disorder and transport properties in the polypyrrole. An effort is made to correlate the transport properties to the morphology by probing disorder via two different spectroscopic techniques. Frequency dependence of both real and imaginary part has shown that disorder and inhomogeneity varies in different PPy devices, which thus affect the transport properties like conductivity and mobility. Mobility values along the thickness direction for each sample reveal the impact of disorder on out-of¬plane geometry. A circuit based on consideration of the distributed relaxation times, is successfully used to obtain the best fit for the Cole–Cole plot of various PPy devices. FWHM of the de-convoluted peaks of Raman spectra is attributed to the change in distribution of the conjugation length in the PPy films. Chapter 5: The main focus of this chapter is the qualitative exploration of different photo-physical and electrical properties of electropolymerized poly(3-hexylthiophene) and their dependence on doping level. Photoluminescence quenching, band edge shifting in absorption spectra, electrochromic effect, significant enhancement in photocurrent at optimum doping level, two relaxation behaviors in reactance spectra and presence of negative capacitance at low frequencies are distinct features which are observed in poly(3-hexylthiophene) in this work. Quenching in photoluminescence intensity is attributed to charge transfer occurring between polymer chains and dopant ions. Two semicircles in the Cole-Cole plots refer to two type of relaxation process occurring in bulk layer and at interface. Frequency response of capacitance at higher bias and lo side of frequency shows a negative capacitance due to the relaxation mechanism associated with the space-charge effect. Chapter 6: Synthesis of quantum dots and fabrication of hybrid devices is one of the catchy parts of this chapter. Huge quenching photoluminescence intensity and very high increment (~ 400 %) in photocurrent clearly depict the charge transfer at molecular level. Temperature dependent current–voltage characteristics show the absence of thermionic emission since the barrier height is more than the thermal energy of the carriers. Further analysis confirms that the charge carrier injection of ITO/PPCdTe3/Al device is controlled by tunneling processes. The hybrid system has shown a peculiar transition from direct tunneling to Fowler–Nordheim tunneling mechanism which is because of the change in shape of the barrier height from trapezoidal to triangular type with increase in applied electric field. Chapter 7: The conclusions of the different works presented in this thesis are coherently summarized in this thesis. Thoughts and prospective for future directions are also summed up.

This diploma thesis studied the interaction of ionic and amphiphilic fluorescent probes with polyelectrolytes. The research of such colloidal system could be helpful in deeper understanding of interactions between polyelectrolytes and surfactants. The aim of this thesis was to determine whether ionic or amphiphilic probes are suitable for this research. Two polyelectrolytes, sodium polystyrene sulfonate and hyaluronan were used in this study. Interactions of polyelectrolytes with fluorescent probes (4-Di-2-Asp, methylene blue, dodecyl acridine orange, DiO and DiA) were studied in this work. Then cationic surfactant cetyltrimethylamonium bromide was added to this system. Samples were studied using fluorescence and UV/VIS spectroscopy. Emission and absorption spectra of these probes were recorded. This experiment was based on hypothesis that due to positive charge these probes will bind to the negatively charged polyelectrolyte. Formation of dimers or other aggegates was presumed for fluorescent probes dodecyl acridine orange and methylene blue. When 4-Di-2-Asp was used,changes in fluorescence intensity and absorption spectra in connection with possible formation of aggregates was supposed to be observed. It should be noted that formation of dimers for 4-Di-2-Asp is not described in literature. The formation of dimers wasn't clearly demonstrated during the measurement. Formation of dimers was observed only with dodecyl acridine orange. Probes DiO and DiA were used only in the study of the interaction with polyelectrolytes. These fluorescent probes showed up as inappropriate, because they adsorbed on tube walls. When cationic surfactant was added to hyaluronan-fluorescent probe system, surfactant pushed away fluorescent probe and bonded electrostatically to negatively charged groups of polyelectrolyte.

The deprotonation characteristics of fluorescent probes -naphthol and 8-hydroxypyrene-1,3,6-trisulphonic acid (HPTS) were studied in this diploma thesis, using steady-state and time-resolved fluorescence spectroscopy. Two cationic surfactants, Septonex and cetyltrimethylammonium bromide (CTAB), were studied. These surfactants were measured in the complex with hyaluronan (1.75 MDa, 1 MDa and 300 kDa). Steady-state fluorescence was used for determination of critical aggregation concentration of each surfactant and pKa*. Time-resolved fluorescence decays were used to calculate the average lifetimes and the deprotonation constants of naphthol and HPTS. The measurement with hyaluronan were compared with the polystyrenesulfonate (PSS) – surfactant system. The effect of hydration shell of hyaluronan on hyaluronan – surfactant complex formation results from the comparison of above mentioned systems. Large differences were found in the deprotonation characteristic between surfactants and even between individual molecular weights of hyaluronan. The measurement shows that the hydration shell is located near to the dissociated carboxyl groups of hyaluronan chain, where the interaction with the positively charged surfactants occurs. Furthermore, the aggregation number of Septonex was determined by quenching of pyrene using cetylpyridinium chloride (CPC) as a quencher. The aggregation number for 20 mM Septonex solution was determined as a value of 104 molecules. CPC was used for confirmation of the localization of -naphthol in the micelles of CTAB and polymer – CTAB, respectively.

Die vorliegende Dissertation behandelt die Synthese und Charakterisierung neuartiger hetero- und homoleptischer Carboxylato- und Sulfonatobismut(III)verbindungen, die Potential für antimikrobielle Anwendungen und/oder als Präkursoren für röntgenopake organisch-anorganische Hybridmaterialien aufweisen. Als Ausgangsstoffe dienten Arylbismutane, deren supramolekulare Strukturen in Abhängigkeit der funktionellen Gruppe am organischen Substituenten mit dem Ziel der Analyse intermolekularer Metall∙∙∙π(Aryl)-Wechselwirkungen sowie deren Einfluss auf die Ausbildung von Polymorphen diskutiert werden. Die Einstellung der Reaktionsbedingungen bei den Umsetzungen dieser Organobismutverbindungen mit Carbon- oder Sulfonsäuren erlaubt die gezielte Synthese carboxylato- oder sulfonatosubstituierter Koordinationspolymere des Bismuts unter milden Bedingungen. Neben der Beschreibung der Strukturen wird das Verhalten dieser Verbindungen in Lösung besprochen. Zur Aufklärung der Bildungsmechanismen von Bismutoxidoclustern wurden Hydrolyse- und Kondensationsstudien ausgehend von Lösungen der Bismutcarboxylate und -sulfonate sowie polynuklearer Modellverbindungen durchgeführt. Die in diesem Verlauf isolierten, funktionalisierten Bismutoxidospezies vertiefen die Erkenntnisse zum strukturellen Aufbau sowie zum Reaktionsverhalten der nanoskaligen Moleküle. Dabei werden u. a. die Symmetrieelemente der Bismutoxidocluster sowie Clusterabbaureaktionen beschrieben. Die Charakterisierung der synthetisierten Verbindungen erfolgte mittels Einkristallröntgenstrukturanalyse, Pulverröntgendiffraktometrie, Infrarot- und Kernspinresonanzspektroskopie sowie thermischen Analysemethoden.

The most important substances of the group of perfluorinated compounds are perfluorooctyl sulfonate (PFOS), perfluorooctanoic acid (PFOA) and perfluorooctane sulphonamide (FOSA). Perfluorinated compounds have special physical and chemical properties, which make them valuable for usage in different industrial branches. These properties, which make them so useful are also the reason, why they are so harmful for the environment. The target of theoretical part of the diploma thesis was processing of literature searche on the topic: Evaluation of environmental load by perfluorinated compounds. In the experimental part was developed and optimized a method that was used for the identification and quantification of selected pollutants contained in real soil samples.

Molecular dynamics simulation was used to study ion permeation through different membrane proteins embedded in a lipid bilayer (DMPC) with different saline solutions. The potential of mean force (PMF) for ion transport was obtained by umbrella sampling simulations. A revised MacKerell force field for tryptophan residues was studied using gramicidin A (gA) channel as a test model. The revised force field contribution to the Na+ PMF was consonant with the prediction from the experimental results, but in stark contrast to the prediction of the CHARMM force field, version 22, for the tryptophan side-chain. A new grid-based correction map algorithm by MacKerell group, called CMAP, was introduced into the CHARMM force field, version 31. The CMAP algorithm focused on optimizing phi, psi dihedral parameters for the peptide backbone. The CMAP corrections reduced the excessive translocation barrier. Decomposition demonstrated the reduction in the translocation barrier was due to effects on the K+ PMFH2O rather than on K+ PMFgA. The presence of negatively charged sulfonate group at the entrance and exit of the gA channel affected the depth and the location of the highly occupied sites. The negatively charged sulfonate group produced a strong attraction for the cations in the bulk towards the channel mouth. In the M2 transmembrane domain channel (M2-TMD), three M2-TMD structures were studied, differing only in whether the selectivity-filter (four His37 side-chains) was uncharged, +2 charged, or +3 charged. M2-TMD structural properties were compared with the structural properties of other models extracted from NMR and X-ray studies. The spontaneous cation and anion entry into the charged selectivity-filter was different from that into a neutral selectivity-filter. Cl- ions had a lower free-energy barrier in the selectivity-filter than either Na+ or NH4+ ions through the M2-TMD channel. NH4+ ions had a lower free-energy barrier in the selectivity-filter than Na+ ions. Based on accessible rotamer conformations, a revised conductance mechanism was proposed. In this conductance mechanism, the His37 side-chain functioned as an acceptor and donor group, whereas the Trp41 side-chain functioned as a carrying group.

Les substances perfluoroalkylées (PFAS) sont des composés synthétiques utilisés dans une multitude de domaines pour leurs propriétés hydrofuges, antiadhésives et antitaches exceptionnelles. Cependant, ces contaminants, dont la neurotoxicité a été démontrée dans les études in vitro et in vivo, sont capables de traverser la barrière placentaire et d’atteindre le fœtus en développement. Bien qu’une multitude d’études épidémiologiques aient été conduites pour examiner l’association entre l’exposition prénatale aux PFAS et le neurodéveloppement des enfants, il n’y a pas de consensus dans la littérature : certaines rapportent des associations délétères, et d’autres protectrices ou nulles. Le but de cette étude est d’évaluer l’association entre l’exposition aux PFAS chez les femmes enceintes et le développement neurocomportemental et social des enfants pendant la petite enfance. Nous avons également examiné si le lien différait entre les filles et les garçons. Les données de l’étude Maternal-Infant Research on Environmental Chemicals (MIREC), une cohorte de grossesse pancanadienne, ont été utilisées. L’exposition prénatale à trois PFAS (acides perfluorooctanoïque (PFOA), perfluorooctanesulfonique (PFOS) et perfluorohexane sulfonique (PFHxS)) ainsi que leur somme (ΣPFAS) a été mesurée dans le plasma maternel prélevé durant le premier trimestre de grossesse. Lorsque les enfants étaient âgés de trois-quatre ans, les mères ont été invitées à remplir deux questionnaires sur leurs enfants : le Behaviour Assessment System for Children–2 (BASC-2), pour évaluer les difficultés émotionnelles et comportementales, et le Social Responsiveness Scale–2 (SRS-2), afin d’évaluer le développement social. À partir des données de 794 paires mère-enfant, des analyses de régressions linéaires multiples, avec ajustement pour des facteurs de confusion, ont été réalisées, et les coefficients d’association ont été calculés pour un doublement des concentrations de PFAS. La modification des associations selon le genre a été examinée au moyen de termes d'interaction et d'analyses stratifiées. Bien que la majorité des associations obtenues soient nulles, pour l’ensemble du groupe étudié, un doublement de l’exposition prénatale aux PFOS était lié à moins de déficits de motivation sociale (β = -1.03; IC : -1.88, -0.17) et le PFHxS à plus de comportements atypiques (β = 0.57; 0.04, 1.11). Cependant, les analyses selon le genre ont révélé que chez les garçons seulement, un doublement de l’exposition prénatale aux PFOA était significativement associée à des scores plus faibles pour les sous-échelles suivantes : indice des symptômes comportementaux, problèmes d'externalisation, agressivité et hyperactivité (β allant de -1.87 à -1.32). Le PFOS et la ΣPFAS étaient aussi liés à moins d’agressivité chez les garçons (β = 1.20; -2.27, -0.13 et β = -1.35; -2.55, -0.15 respectivement). À l’inverse, chez les filles, le PFOA était significativement lié à plus de symptômes d’anxiété, et le PFHxS et la ΣPFAS étaient liés à plus de problèmes de cognition sociale (β allant de 0.90 à 1.81). Dans l’ensemble, les données suggèrent que l’association entre l’exposition prénatale aux PFAS et le développement neurocomportemental et social des enfants semble différer selon le genre : un effet protecteur est observé chez les garçons, tandis qu’il ressort délétère chez les filles. Les résultats obtenus dans cette cohorte canadienne de grande taille corroborent ceux notés dans certaines études épidémiologiques rapportant un lien délétère, lequel est surtout observable chez les filles. / Perfluoroalkyl substances (PFAS) are synthetic compounds used in a wide range of fields for their exceptional water-repellent, non-stick, and stain-resistant properties. However, these contaminants, whose neurotoxicity has been demonstrated in in vitro and in vivo studies, can crossthe placental barrier, and reach the developing fetus. Although numerous epidemiological studies have been conducted to examine the association between prenatal exposure to PFAS and the neurodevelopment in children, there is no consensus in the literature: some report deleterious associations, while others report protective or null associations. The aim of this study is to investigate the association between PFAS exposure in pregnant women and the neurobehavioral and social development of children during early childhood. We also examined whether the association differed between girls and boys. We used data from the Maternal-Infant Research on Environmental Chemicals (MIREC) study, a pan-Canadian pregnancy cohort. Prenatal concentrations of three PFAS (perfluorooctanoic (PFOA), perfluorooctanesulfonic (PFOS) and perfluorohexanesulfonic acids (PFHxS)), as well as their sum (åPFAS), were measured in maternal plasma collected during the first trimester of pregnancy. When the children were three to four years old, mothers were asked to complete two questionnaires about their children: the Behaviour Assessment System for Children-2 (BASC-2) to assess emotional and behavioural difficulties, and the Social Responsiveness Scale-2 (SRS-2) to assess social development. Using data from 794 mother-child dyads, multiple linear regression analyses, with adjustment for confounding factors, were performed and regression coefficients were estimated to assess whether there was an association between each doubling of PFAS concentrations and test scores. Effect modification by child gender was examined using interaction terms and stratified analyses. For the entire study group, although most of the associations found were null, a doubling of prenatal PFOS exposure was linked to fewer social motivation deficits (β = -1.03; CI: -1.88, -0.17), and increased PFHxS was linked to more atypical behaviors (β = 0.57; 0.04, 1.11). However, gender-stratified analyses revealed that in boys only, each doubling of prenatal PFOA exposure was significantly associated with lower scores on the following BASC-2 subscales: Behavioral Symptoms Index, Externalizing Problems, Aggressivity and Hyperactivity (β ranging from -1.87 to -1.32). PFOS and åPFAS were also associated with less aggression in boys (β = 1.20; -2.27, -0.13 and β = -1.35; -2.55, -0.15 respectively). Conversely, in girls only, PFOAwas significantly associated with more symptoms of anxiety, and PFHxS and ∑PFAS were associated with more social cognition problems (β ranging from 0.90 to 1.81). Overall, the data suggest that the association between prenatal PFAS exposure and the neurobehavioral and social development of children appears to differ by gender: a protective effect is observed in boys, while a detrimental effect is seen in girls. The results obtained in this large Canadian cohort are consistent with findings from some epidemiological studies reporting a harmful link predominantly in girls.

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