Self-assembly is a process of non-intrusive transformation of a system from a disordered to an ordered state. For engineering purposes, self-assembly of microscopic objects can benefit significantly from macroscopic guidance and control. This dissertation is concerned with controlling self-assembly in binary monolayers of electrically charged particles that follow basic laws of statistical mechanics. First, a simple macroscopic model is used to determine an optimal thermal control for self-assembly. The model assumes that a single rate-controlling mechanism is responsible for the formation of spatially ordered structures and that its rate follows an Arrhenius form. The model parameters are obtained using molecular dynamics simulations. The optimal control is derived in an analytical form using classical optimization methods. Two major lessons were learned from that work: (i) isothermal control was almost as effective as optimal time-dependent thermal control, and (ii) neither electrostatic interactions nor thermal control were particularly effective in eliminating voids formed during self-assembly. Accordingly, at the next stage, the focus is on temperature-pressure control under isothermal-isobaric conditions. In identifying optimal temperature and pressure conditions, several assumptions, that allow one to relate the optimal conditions to the phase diagram, are proposed. Instead of verifying the individual assumptions, the entire approach is verified using molecular dynamics simulations. It is estimated that under optimal isothermal-isobaric conditions the rate of self-assembly is about five time faster than that under optimal temperature control conditions. It is argued that the proposed approach of relating optimal conditions to the phase diagram is applicable to other systems. Further, the work reveals numerous and useful parallels between self-assembly and crystal physics, which are important to exploit for developing robust engineering self-assembly processes. / text

1-eicosanethiolate molecules form relatively weak bonds with the surface of InSb(100) limiting the order of the self-assembled monolayer despite the long length of the alkyl chain. Heating to only 225 °C in vacuum completely desorbed the eicosanethiolate layer from the surface based on x-ray photoelectron spectroscopy. Even after deposition times as long as 20 h in ethanol, the asymmetric methylene stretch was at 2925 cm-1 in the attenuated total reflection Fourier transform infrared spectrum, which is indicative of alkane chains that are incompletely ordered. Atomic force microscopy images combined with ellipsometry showed that the eicosanethiolate layer conformed to the rough InSb(100) starting surface (2.3±0.2 nm RMS). The reoxidation kinetics in air of InSb(100) and InSb(111)B covered with eicosanethiolate layers was the same despite the lower surface roughness of the latter (0.64±0.14 nm). The bond that the S head group makes with the substrate is the primary factor that determines the cohesiveness of the molecules on the surface. Although interactions between the alkane chains in the layer are sufficient to form a self-assembled layer, the fluidity of the molecules in the layer compromised the chemical passivation of the surface resulting in reoxidation in air after 20 minutes.

No description available.

This thesis is focused on the preparation of monosubstituted derivatives of -cyclodextrin ( -CD) which can form supramolecular polymers. These polymers can be utilized in capillary electrophoresis. Set of monosubstituted 2I -O-, 3I -O- a 6I -O-(3-(naphthalen-2-yl)prop-2-en-1-yl) derivatives of -CD was prepared (naphthylallyl derivatives). Reaction was performed by cross metathesis of O-allyl derivatives of -CD with a 2-vinylnaphthalene in yields 16 - 25 %. Hoveyda-Grubbs 2nd generation catalyst was used. Alkylation of -CD with 2-(3-bromoprop-1-enyl)naphthalene followed by peracetylation of remaining hydroxyl groups and separation of isomers resulted in the per-O-acetyl-3I -O- a per-O- acetyl-6I -O-(3-(naphthalen-2-yl)prop-2-en-1-yl)- -CD in yields 5 and 1 %. A set of dimers of -CD 1,4-bis( -CD-2I -O-yl)-but-2-ene, 1,4-bis( -CD-3I -O-yl)-but-2-ene and 1,4-bis( - CD-6I -O-yl)-but-2-ene was prepared, too. Reaction was performed by cross metathesis of O-allyl derivatives of -CD in yields 1 - 8 % using again Hoveyda-Grubbs 2nd generation catalyst. The dimers of naphthalene guests (1,2-bis(naphthalen-2-yl)ethene and 1,2-bis(naphthalen-2-yl)ethane) for preparation of complexes with CD dimers were also prepared. Further optimization of synthesis of naphthylallyl derivatives of -CD was carried out. These...

In this work we have explored the possibility of using surfactant/polyelectrolyte complexes as templates to synthesize inorganic mesostructured materials mainly with a film morphology. Inorganic species deposit in those regions of the films which are filled with a polymer hydrogel, surrounding the arrays of ordered surfactant micelles. This method produced thick robust films where the inorganic regions are reinforced and functionalized by the polymer, thus these materials are expected to have potential applications in separation, absorption, catalysis and chemical sensing. Initial work involved mixing silicate precursors directly into CTAB/PEI solutions to form highly ordered 2D hexagonal silica films at the air/water interface. Time resolved synchrotron SAXS allowed investigation of processes occurring in solution during the reaction, from which a film growth mechanism was proposed. Films had good thermal properties and after post-synthesis TMOS vapour treatment, retained structure upon template removal. Silica gel monoliths with various mesostructures were also rapidly fabricated in one minute with surfactant/LPEI complexes. Cat-ionic surfactant mixtures with polymers were also employed to template silica films with different cubic mesostructures at the air/water interface. The mesophases of the interfacial films were enriched due to more complicated interactions between the polymers and two surfactants. Polymer molecular weight, total composite concentration, chemical nature of the polymer as well as the cationic-anionic surfactant molar ratio was used to systematically control the silica film mesophase. Robust titania films were also prepared with cat-anionic surfactant mixtures and polymers at the air/water interface. Although the film mesostructure was lost after calcination, the in-situ and dry free-standing films display ordered cubic mesostructures and the films are stable to calcination after post-synthesis treatment. Ordered lamellar iron oxide films templated by SDS/LPEI complexes were also prepared at the air/water interface.

"The design and development of chemically modified surfaces for bioanalytical applications is presented. Chemical surface modification is demonstrated to be a method to control surface properties on the molecular level by selecting the appropriate substrate, linking chemistry, and terminal group functionality. These systems utilize spontaneous interactions between individual molecules that allow them to self-assemble into larger, supramolecular constructs with a predictable structure and a high degree of order. Applications investigated in this thesis include: surface patterning, switchable surface wettability, and biological sensor devices that combine surface based molecular recognition, electrochemical detection methods, and microfluidics. A multilayered approach to complex surface patterning is described that combines self-assembly, photolabile protecting groups, and multilayered films. A photolabile protecting group has been incorporated into molecular level films that when cleaved leaves a reactive surface site that can be further functionalized. Surface patterns are created by using a photomask and then further functionalizing the irradiated area through covalent coupling. Fluorophores were attached to the deprotected regions, providing visual evidence of surface patterning. This approach is universal to bind moieties containing free amine groups at defined regions across a surface, allowing for the development of films with complex chemical and physico-chemical properties. Systems with photoswitchable wettability were developed by fabricating multilayered films that include a photoisomerizable moiety, cis-/trans- dicarboxystilbene. When this functionality was incorporated into a multilayered film using non-covalent interactions, irradiation with light of the appropriate wavelength resulted in a conformational change that consequently changed the hydrophobicity of the substrate. Methods were investigated to increase the reversibility of the photoswitching process by creating surface space between the stilbene ligands. Utilizing mixed monolayers for spacing resulted in complete isomerization for one cycle, while the use of SAMs with photolabile groups produced surfaces that underwent isomerization for three complete cycles. A microfluidic device platform for ion sensing applications has been developed. The platform contains components to deliver small volumes of analyte to a surface based microelectrode array and measure changes in analyte concentration electrochemically in an analogous method to that used in conventional electrochemical cells. Crown ether derivatives that bind alkali metal ions have been synthesized and tested as ionophores for a multi-analyte device of this type, and the sensing platform was demonstrated to measure physiological relevant concentrations of potassium ions. Advantages of this design include: high sensitivity (uM to mM), small sample volumes (less than 0.1 mL), multi-analyte capabilities (multiple working electrodes), continuous monitoring (a flow through system), and the ability to be calibrated (the system is reusable). The self-assembled systems described here are platform technologies that can be combined and used in molecular level devices. Current and future work includes: photopatterning of gold and glass substrates for directed cell adhesion and growth, the design and synthesis of selective ion sensors for biological samples, multi-analyte detection in microfluidic devices, and incorporating optical as well as electrochemical transduction methods into sensor devices to allow for greater sensitivity and self-calibration."

With 500,000 coronary artery bypass procedures performed each year in the United States, and only one-third of patients possessing suitable autologous grafts, there is a clinical need for tissue engineered blood vessels (TEBVs). The overall goal of this project was to develop a one- step approach to rapidly produce entirely cell- derived tubular tissue constructs without scaffold materials. To achieve this goal, we developed "centritubing"-- a system based on applying centrifugal force to suspended cells to create a tube-shaped cellular aggregate. Briefly, rat aortic smooth muscle cells were injected into cylindrical polycarbonate spinning chambers and then spun to apply centrifugal force, which pelletted the cells on the inner wall of the chamber. After three days in culture with growth medium, the cells remodeled to form tissue tubes. In previous work we have shown, in principle, that centritubing produces tubular constructs, however tissue tube production was not consistently achieved. The first objective of this study was to develop modifications to the centritubing device that would lead to consistent lumen diameter, rapid cellular aggregation into a tube construct, and an improved success rate of tube formation. The second objective was to investigate cellular parameters that contribute to tubular tissue construct formation using centritubing. Prior to changes in manufacturing of the centritubing device and culture system, the success rate of centritubing was inconsistent. After these changes, the success rate of tubular construct formation improved to 85% (11/13). Noteworthy modifications to the centritubing device included the addition of a central mandrel as a substrate for tissue contraction, development of a smoother seeding surface, and manufacture of a reusable culture chamber. The results of this study support the proof of concept for centritubing as a device for rapid production of tubular tissue constructs and provide insight for future progress using the centritubing methodology.

Ce travail de thèse propose une nouvelle approche pour la préparation de membranes à matrice mixte basée sur l’utilisation de copolymères à blocs et de nanoparticules inorganiques disposant de propriétés magnétiques. Des aggrégats de copolymères ont été préparés avec une morphologie variée (sphères, cylindres et vésicules) à partir du copolymère poly(acide méthacrylique)-b-poly(méthacrylate de méthyle). Ce dernier a été synthétisé par polymérisation radicalaire contrôlée par transfert de chaîne réversible par addition-fragmentation (RAFT) dans l’éthanol à 70°C. Des particules d’oxyde de fer ont, quant à elles, été préparées en présence de différents stabilisants à température variée pour permettre d’atteindre la charge de surface et les propriétés magnétiques recherchées. La structure des copolymères à bloc a permis d’obtenir à la fois des membranes hydrophobes via le procédé de séparation de phase induite par un non-solvant, ainsi que des membranes hydrophiles lorsque que la technique de spin-coating était appliquée aux aggrégats formés par auto-assemblage induit lors de la polymérisation. Grâce à l’étude détaillée des propriétés de filtration des membranes obtenues, la relation structure-propriété a été discutée sous l’action d’un champ magnétique externe. Enfin, la sensibilité au colmatage a été vérifiée via la filtration de solutions de protéines. Il a ainsi été démontré une diminution notable du colmatage sous champ magnétique, ouvrant de belles perspectives pour ces nouvelles membranes. / This thesis presents a new approach to produce mix matrix membranes using block copolymers and inorganic nanoparticles having magnetic properties. The polymeric nanoparticle with different morphologies (linear, Spheres, worms, and vesicles), from poly (methacrylic acid)-b-(methyl methacrylate) diblock copolymer, were synthesized using Reversible addition−fragmentation chain transfer polymerization (RAFT) in ethanol at 70 ֠C. The inorganic counterpart, iron oxide nanoparticles were prepared using different stabilizers at various temperatures to acquire the necessary surface charge and magnetic properties. The chemistry of the particles leads to form both hydrophobic membranes using non-solvent induced phase separation as well as a hydrophilic membrane by using the simple spin coating technique with the particles from polymerization induced self-assembly. By a detailed experimental study of the membrane filtration, the influence of different parameters on the process performance has been investigated with and without magnetic field. Finally, membrane fouling has been studied using protein solution. Also, the membrane performance was examined under magnetic field revealing the successful reduction in the fouling phenomenon making them new performant membranes in the area of membrane technology.

Les diaryléthènes et leurs dérivés terrylènes sont prometteurs pour la prochaine génération de dispositifs optoélectroniques en raison de leurs excellentes propriétés photochimiques. Pour les rendre viables pour les appareils électroniques miniaturisés, il est nécessaire d'étudier cette classe de molécules au niveau unimoléculaire avec le microscope à tunnel sous vide ultra-élevé (UHV STM). Cette thèse comporte trois parties: 1) développement de terarylènes hautement sensibles à la commutation; (2) leur modification pour les études STM; et 3) les résultats de ces études STM. Pour être étudié à l'échelle de la molécule unique par STM, des terarylènes ayant une sensibilité de commutation élevée ont été sélectionnés. Ces composés présentent des rendements quantiques élevés allant jusqu'à 100%. Cependant, la réaction de cycloréversion reste faible, de sorte qu'une voie alternative, grâce à un mécanisme oxydatif à réaction en chaîne, a été recherchée. Dans une première partie, nous montrons que l'efficacité et la vitesse de cette réaction peuvent être contrôlées par la fixation de groupes aromatiques sur les carbones réactifs. Dans la deuxième partie, nous avons fonctionnalisé ces molécules afin de les étudier par STM en introduisant des groupes tert-butyle et chlorure. Tout en préservant leurs excellentes propriétés photochimiques, les groupes tert-butyle présentent un excellent contraste lumineux dans les images STM, ils minimisent aussi l'agrégation de ces molécules sur la surface et découplent légèrement les molécules de la surface. Les atomes de chlore permettent de contrôler les assemblages moléculaires sur des substrats isolants de type bicouche de NaCl cristalline précédemment déposés sur un substrat métallique. Dans la troisième partie, les résultats de STM sont présentés. Nous avons développé une nouvelle approche ascendante pour la formation reproductible de nano-assemblages du terarylène non modifié à 77 K. Quant au terarylène modifié par les groupes tert-butyle, il présente à 5 K sur une surface d'Ag (111) différentes formes qui, grâce à la position des groupes tert­butyles à contraste élevé et à l'aide de calculs DFT, ont pu être assignées comme étant différentes conformations de surface de la molécule. Sur NaCl / Ag (111), il a été possible de visualiser les états occupés et inoccupés de la molécule. Cela illustre que, pour ces applications, des molécules avec des propriétés appropriées peuvent être des candidates intéressantes pour des études STM afin d'obtenir des informations sur leurs propriétés à l'échelle de la molécule unique. De telles molécules peuvent être optimisées pour tenir compte de la surface, car sa simple présence peut induire un comportement bien différent de celui obtenu en solution. Cette thèse ouvre les terarylènes à des applications futures nécessitant une surface solide. / Photoswitching diarylethenes, and their terarylene derivatives, are promising for the next generation optoelectronic devices because of their excellent photochemical properties. To make them viable for miniaturized electronic devices, it is necessary to study this class of molecules at the single molecular level by scanning tunneling microscopy under ultra-high vacuum (UHV STM). This thesis has three parts: 1) development of terarylenes highly sensitive to switching; (2) their modification for STM studies; and 3) results of STM investigations. To be studied at the single molecular level by STM, terarylenes with high switching sensitivity have been selected. These compounds display high quantum yields of up to 100 %. However, the cycloreversion reaction remains low so an alternative route, through a chain-reaction oxidative mechanism, has been sought. In the first part, we show that the efficiency and speed of this reaction may be controlled by attachment of aromatic groups on the reactive carbons. In the second part, we functionalized these molecules for STM studies by attaching tert-butyl and chloride groups. These substituents preserve their excellent photochemical and switching properties while tert-butyl groups show bright contrast in STM images, minimize aggregation of these molecules on the surface, and slightly decouple the molecule from the surface. The chlorine group has been introduced to direct their surface assembly on insulating substrates composed of crystalline NaCl bilayer previously grown over a metallic substrate. In the third part, results of STM are presented. We developed a new bottom-up approach for forming reproducible nanoassemblies of the unmodified terarylene at 77 K. Meanwhile, at 5 K, the terarylene functionalized with tert-butyl groups present different forms on the Ag(111) surface. From the positioning of the high-contrast tert-butyl groups and with the aid of DFT calculations, we assign different conformations of the molecule on the surface. On NaCl/Ag(111), direct visualization of the occupied and unoccupied states could be achieved. This illustrates that for these applications, molecules with appropriate properties can be interesting candidates for STM studies to obtain information at the single molecular level. Such molecules may be redesigned with a consideration of the surface as its mere presence may induce behavior previously unobserved or neglected if they were studied in solution. This thesis opens terarylenes to future applications which require a solid surface.

Metallosupramolecular self-assembly has fast expanded as a field due to the possibility for relatively facile construction of large assemblies through reversible non-covalent interactions, compared to their more synthetically challenging covalent counterparts. Not least, it provides a fast and often quantitative route to the construction of three-dimensional structures with a cavity. These internal spaces have been shown to be effective for a variety of applications, including but not limited to catalysis, drug delivery, use as a noncovalent protecting group, a separations material etc. Thermodynamic processes, with the inherent advantages of atom efficient, high-yielding reactions, usually control these systems. However this can also be a double-edged sword, with these systems susceptible to changes to specific ambient conditions, and are thus often not kinetically stable. Herein, we report the expansion of a method utilising the one electron oxidation of high spin d7 cobalt(II) to low spin d6 cobalt(III) as a molecular locking mechanism as part of the assembly process. This allows for the formation of species under thermodynamic control in the CoII manifold, with the kinetic stability of these assemblies in the oxidised CoIII and has been used to synthesise a variety of tetrahedra and helicates with a series of bis-bidentate N,N’-chelate ligands, which have shown to be stable away from their thermodynamically preferred conditions for long periods of time. These containers can be made both water and organic soluble via counteranion exchange, and a series of guests have been shown to bind in the tetrahedral species. Alongside on going biological viability tests, these guests show promise for a variety of applications including fluorescent tagging and radio-diagnostic agents. Novel switching methods have also been demonstrated for transformations between these species going both energetically down and up hill.