<p>Detailed characterization of size and shape of polymers, and development of methods to elucidate the mechanisms behind shape transitions are central issues in this thesis. In particular we characterize grafted polymer chains under confinement in terms of the chain entanglement complexity and mean molecular size. Confinement of polymers into small regions can drastically affect the structural and mechanical properties, and make these systems convenient for a large number of applications, including the design of lubricants, coatings, and various biotechnical applications.</p><p>Using Monte Carlo simulations with a model including both persistence length and intramolecular non-bonded interaction, we find two regimes of polymer behaviour: <i>i) soft mushrooms</i>, where confinement successively flattens the chains with accompanying change in the folding complexity, and <i>ii) hard mushrooms </i>where the compact structures appear to resist confinement and the only way to reorganize the entanglements is by flattening under strong confinement. We also show that a simultaneous use of mean molecular size and chain entanglement complexity renders the possibility to create configurational "phase" diagrams for a wide range of polymers. We have further introduced a new descriptor of folding complexity, <i>the path-space ratio</i>, ζ_α which captures essential features of molecular shape beyond those conveyed by mean size and asphericity.</p><p>This thesis also contains results of light scattering measurements on supramolecular complexes formed when mixing an adamantane end-capped star polymer with a β-cyclodextrin polymer. The specific interactions result in an interplay between the association of the end-caps and a strong inclusion interaction between adamantane and β-cyclodextrin.</p>

The aim of this study was to investigate the molecular interactions of the anti-cancer drug Doxorubicin (DOX) with poly(methacrylic acid) grafted starch nanoparticles (PMAA-g-St). In order to fully understand the DOX/PMAA-g-St system, we conducted in-depth studies on DOX dimer dissociation and DOX/PMAA-g-St binding interactions using various techniques such as isothermal titration calorimetry (ITC), dynamic light scattering (DLS), and fluorescence and absorption spectroscopy. Based on our experimental results, we developed a quantitative thermodynamic model with relevant parameters such as dissociation constant, Kd, as well as enthalpy of binding, ΔH, in order to explain DOX/PMAA-g-St interactions. In addition, we also studied the effect of environmental factors such as pH and NaCl on DOX self-association and DOX/PMAA-g-St complex formation. In conclusion, the combination of results obtained from various techniques as well as the multispecies equilibrium model, enables us to interpret quantitatively the data of drug loading onto and release from polymeric nanoparticles.

This thesis describes the results of experimental work on polyelectrolyte gels and their interaction with oppositely charged surfactants, and presents two new algorithms applicable to the simulation of colloid and polymer systems. The model systems investigated were crosslinked poly(acrylate) (PA) and poly(styrene sulphonate) (PSS), and the surfactant was dodecyl trimethylammonium bromide (DoTAB). Pure gel materials were studied using dynamic light scattering. It was shown that the diffusion coefficient (D) increases with increasing degree of swelling and the concentration dependence is larger than predicted by scaling arguments. For gels at swelling equilibrium D increases with increasing degree of crosslinking. In subsequent studies on gel particles in DoTAB solution, Raman spectra were recorded at different positions in the gel. For both types of gels two distinct regions could be observed. For PA the surfactant is localised in the outer phase without any surfactant in the core, while for PSS the surfactant was distributed such that it had the same concentration relative to the polymer throughout the gel. In a second experiment, the kinetics for the deswelling of microscopic PSS particles in DoTAB solution was studied. It was found that the final volume varied linearly with the DoTAB concentration, and the rate of volume decrease could be fitted to a single exponential indicating stagnant layer diffusion to be the rate limiting process for the deswelling of the PSS particles. In the second part, I first describe an algorithm showing an efficient way to detect percolation in simulations, with periodic boundary conditions, using recursion. Spherical boundary conditions is an alternative to periodic boundary conditions for systems with long-range interactions. In the last part, the possibility to use the surface of a hypersphere in four dimensions for simulations of polymer systems is investigated, and algorithms for Monte Carlo and Brownian dynamics simulations are described.

Polyaniline was chemically synthesized at three different temperatures of 25, 0, and -25oC, by oxidative polymerization with ammonium peroxidisulfate at equimolar of aniline to oxidant ratio and 1M HCl. The resulted polyaniline was in a powder form which was characterized by several techniques such as: electrical conductivity, elemental analysis, thermal analysis, wide-angle X-Ray diffraction, and scanning electron microscope. The solution properties of the reduced polymer were studied by viscometry, static and dynamic light scattering. It was found that as the polymerization temperature decreased, the molecular weight, crystallinity, and thermal stability of polyaniline increased, while the electrical conductivity was independent of the polymerization temperature. Moreover, the morphology of the polymer was changed from granular to tubular with reducing polymerization temperature. Viscometry and static light scattering showed that polyaniline has a flexible random coil conformation when dissolved in N-methyl-2-pyrrolidinone which proved to be a good solvent for this polymer. Dynamic light scattering indicated that the polymer solution is a polyelectrolyte with high hydrodynamic radius at low polymer concentrations. All mechanical features except Young&#039 / s modulus of polyaniline-filled low density polyethylene composites became poorer as polyaniline content increased. Moreover, a sudden increase in the electrical conductivity with increasing polyaniline contents was also observed. The conductivity of the tubular composites of multi wall nanotubes (MWNTs)-filled polyaniline increased with increasing MWNTs loading, and became weakly temperature dependent. The morphological analysis indicated that the MWNTs were well dispersed and isolated, and the tubes became crowded proportionally to MWNTs weight percent used in the composites.

Dynamic light scattering (DLS) is a method to size submicron particles by measuring their thermal motion (diffusion) in suspensions and emulsions. However, the validity of the Stokes-Einstein equation that relates the diffusion coefficient and the particle size is limited to spherical particles and very low concentrations. Within this thesis, DLS is used for the characterization of suspensions of pyrogenic silica which consists of fractal-like aggregates composed of sintered spherical primary particles. These structural features clearly complicate the understanding of DLS experiments and have been a severe obstacle to employing DLS as routine standard tool for the characterization of pyrogenic silica. The main objective of this thesis is therefore to evaluate the application of DLS in product development and quality assurance of pyrogenic silica industry, what essentially means to identify those structural properties of fractal aggregates which are measurable with DLS and to quantify the method’s sensitivity to changes in these properties. The investigations presented here are split up into four parts, simulations that establish a relation between structural and hydrodynamic properties, experiments validating the simulation results, the characterization of concentrated suspensions and the application-oriented analysis of DLS data for specific industrially relevant measurement tasks. / Die Dynamische Lichtstreuung (DLS) ist eine Messmethode zur Größenbestimmung submikroner Partikel. Dabei wird primär die stochastische Bewegung der Teilchen (Diffusion) in Suspensionen und Emulsionen bewertet. Die Stokes-Einstein Gleichung, die das Verhältnis zwischen gemessenem Diffusionskoeffizienten und Partikelgröße wiedergibt, ist jedoch nur für kugelförmige Teilchen, die in sehr niedriger Konzentration vorliegen, gültig. In der vorliegenden Arbeit wird die dynamische Lichtstreuung zur Charakterisierung von Suspensionen pyrogener Kieselsäure eingesetzt. Diese besteht aus fraktalen Aggregaten, die wiederum aus versinterten aber meist kugelförmigen Primärpartikeln zusammengesetzt sind. Diese strukturellen Eigenschaften erschweren die Anwendbarkeit der DLS bzw. die Interpretation der Messergebnisse und verhinderten bisher den Einsatz der DLS als Routinemethode zur Charakterisierung pyrogener Kieselsäuren. Das Hauptziel dieser Arbeit ist daher eine Bewertung der Möglichkeiten der DLS für die Produktentwicklung und Qualitätssicherung in der Herstellung pyrogener Kieselsäuren. Das bedeutet im Besonderen, dass sowohl die messbaren granulometrischen Eigenschaften als auch die Sensitivität der Methode bei Eigenschaftsänderungen ermittelt werden müssen. Die hier durchgeführten Arbeiten sind in vier Teile gegliedert: Simulationen, die eine Beziehung zwischen strukturellen und hydrodynamischen Eigenschaften herstellen, Experimente zur Validierung der Simulationsergebnisse, die Charakterisierung konzentrierter Suspensionen und die anwendungsorientierte Auswertung von DLS-Daten für spezifische industrierelevante Messaufgaben.

The light scattering methods were used for characterization of properties and formation of networks of different dimension, based on N-vinylcaprolactam (VCL). Formation of PVCL microgels in presence of poly(vinyl alcohol) as stabilizer was studied. Size of resulting microgels strongly depends on the temperature and heating rate: interparticle aggregation was observed during slow heating and intraparticle collapse during fast heating. Angular dependence of measured diffusion coefficient on the angle of observation was studied for the microgel in the swollen, shrunken and aggregated states. Thermo-sensitive microgels based on N-vinylcaprolactam and acetoacetoxyethyl methacrylate were prepared under surfactant free conditions. The presence of internal part with low thermo-sensitivity and highly thermo-sensitive outer part of the particle (the core-shell structure of microgel) was deduced from static and dynamic light scattering experiments. Results obtained from combined SLS and DLS show the change of conformation from &amp;quot;swollen&amp;quot; soft sphere to compact shrunken &amp;quot;hard sphere&amp;quot;. Thermo-sensitive microgel based on N-vinylcaprolactam and N-vinylpyrrolidone was used for investigation of the internal modes in microgel dispersion in the wide range of qRg values. Two internal motions and translation diffusion were observed in the asymptotic range. Angular dependence of the normalized diffusion coefficient showed power law behavior in this range. The experimentally determined value of exponent n = 0.96 was in good agreement with the value predicted for ZIMM limit for polymer chains with hydrodynamic interaction. The reduced first cumulant Ã*(q) reached a constant value in the range of large qRg values. Appearance of plateau value indicates ZIMM limit of hydrodynamic interaction but experimental value was much lower than the theoretically predicted plateau value for linear chains in good solution. 3,3?-(ethane-1,1-diyl)bis(1-vinyl-2-pyrrolidone) was used as a cross-linker of VCL in solution by radical polymerization. The network formation was investigated by dynamic light scattering. It was shown, that monitoring of the light scattered intensity in all cases is quite sensitive to detect the gelation threshold even in the presence of very low amount of cross-linker. The power law of time correlation function at the gel point is a sufficient but not a necessary condition for critical gelation. The exponent calculated from power law depends on cross-linker concentration and can be attributed to the degree of branching. Critical exponents obtained at the gel point by DLS and rheology for hydrogel system based on VCL and hydroxyethyl methacrylate were compared. The theoretically predicted equality of exponents from these methods was found as not valid at least for this studied system.

Nonlinear optics is well known to be a highly powerful tool to investigate the properties of the materials. In this thesis we used two important nonlinear optical techniques known as Electric Field Induced Second Harmonic Generation (EFISH) and Harmonic Light Scattering (HLS) to study the first hyperpolarizability of various molecular objects. Firstly, we evidenced the pi donor conjugation in cyclometallated Ir complexes. We have also explored the series of trinuclear organometallic triaryl-1, 3, 5-triazinane-2, 4, 6-triones functionalized by d6-transition metal acetylides complexes at their periphery- large hyperpolarizabilities, far higher than those of related purely organic derivatives are reported. Secondly, a series of dipolar and octupolar dithienylethene (DTE)-containing 2, 2-bipyridine ligands with different metal ions featuring two, four and six photochromic dithienylethene units have been synthesized and fully characterized. The study reveals a large increase in the hyperpolarizability after UV irradiation and subsequent formation of ring-closed isomers. This efficient enhancement clearly reflects the delocalization of the pi-electron system and the formation of strong push&pull chromophores in the closed forms. Thirdly, we have investigated NLO properties of bis (phthalocyaninato) lanthanide-(III) double-decker complexes with crosswise ABAB (phthalocyanine bearing alternating electron-donor and electron-acceptor groups), AB3 (3 donor groups), A4 (4 donor groups) and B4 (no donor groups) ligands. First-order hyperpolarizability is measured and displays the highest quadratic hyperpolarizability ever reported for an octupolar molecule. The direct contribution of f-electrons in coordinated lanthanides ions is also observed on second order nonlinear activity. Finally, gold nanospheres (AuNSs) and gold nanorods (AuNRs) with different aspect ratios (AR) ranging from 1.7 to 3.2 nm have been synthesized by Radiolysis method. Second harmonic intensity collected from AuNRs is clearly higher than that of the nanospheres and reveals their dependence on the AR. We have also mixed the chromophore 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) derivative with AuNRs and observed the enhancement of DAST NLO properties in the presence of AuNRs. A clear increase in the hyperpolarizability (by a factor of 8) of DAST derivatives has been evidence.

This work describes the system for the light scattering measurements in a wide spectral range, which uses the light parametric oscillators and harmonic generators pumped with a nanosecond pulses and summarizes the research in various types of coatings on optical components and inside nonlinear optical crystals. The total scattering losses for the first time were characterized in the infrared region for a new promising in nonlinear optics LiInS2 and LiInSe2 crystals. It was shown that the laser scattering tomography, previously used for investigation of volume defects in semiconductor crystals, can be applied in the nonlinear optical quality control. / Šiame darbe yra aptariama sklaidos matavimo sistema sukurta plačioje spektro srityje reikalingiems matavimams atlikti. Joje naudojami parametriniai šviesos generatoriai bei harmonikų generatoriai, kaupinami nanosekundinės trukmės impulsais, ir apibendinami sklaidos tyrimai, atlikti įvairių tipų optinėse dangose ir netiesiniuose optiniuose kristaluose, naudojant derinamojo bangos ilgio lazerinius impulsus. Pirmą kartą buvo ištirti naujų netiesinėje optikoje perspektyvių LiInS2 ir LiInSe2 kristalų sklaidos nuostoliai infraraudonojoje srityje. Taip pat parodyta, kad koherentinės sklaidos tomografijos metodas, anksčiau taikytas puslaidininkinių kristalų tūriniams defektams tirti, yra tinkamas ir netiesinėje optikoje naudojamų kristalų kokybės tyrimams.

While much is known about the structure and interactions of the β-carboxysomal proteins, interactions of the proposed vertex protein CcmL with the other components have not yet been directly demonstrated. A fluorescence resonance energy transfer based method combined with other complementary spectrophotometry techniques as well as x-ray crystallography and transmission electron microscopy was used in a Thermosynechococcus elongatus BP-1 model to study these interactions. CcmL was found to interact with the various CcmK shell proteins with a clear binding preference for CcmK2; the previously proposed interaction of CcmL with CcmM was shown to not occur in vitro, and a possible CcmL-CcmL interaction was observed tentatively. In addition, analysis of a novel x-ray crystal structure of Nostoc sp. PCC7120 CcmL in a decameric form suggests a possibility of a CcmL-CcmL back-to-back interaction. This study gives the first direct experimental evidence for the biological role of CcmL as the carboxysomal vertex protein.

Detailed characterization of size and shape of polymers, and development of methods to elucidate the mechanisms behind shape transitions are central issues in this thesis. In particular we characterize grafted polymer chains under confinement in terms of the chain entanglement complexity and mean molecular size. Confinement of polymers into small regions can drastically affect the structural and mechanical properties, and make these systems convenient for a large number of applications, including the design of lubricants, coatings, and various biotechnical applications. Using Monte Carlo simulations with a model including both persistence length and intramolecular non-bonded interaction, we find two regimes of polymer behaviour: i) soft mushrooms, where confinement successively flattens the chains with accompanying change in the folding complexity, and ii) hard mushrooms where the compact structures appear to resist confinement and the only way to reorganize the entanglements is by flattening under strong confinement. We also show that a simultaneous use of mean molecular size and chain entanglement complexity renders the possibility to create configurational "phase" diagrams for a wide range of polymers. We have further introduced a new descriptor of folding complexity, the path-space ratio, ζα which captures essential features of molecular shape beyond those conveyed by mean size and asphericity. This thesis also contains results of light scattering measurements on supramolecular complexes formed when mixing an adamantane end-capped star polymer with a β-cyclodextrin polymer. The specific interactions result in an interplay between the association of the end-caps and a strong inclusion interaction between adamantane and β-cyclodextrin.