Fullerene research has advanced to elevated levels in a short period of time due to the unique chemical and physical properties of the caged molecule that have been utilized in numerous applications. Due to the spherical shape of the fullerene molecule which allows for a hollow cavity, encapsulation of atoms or small molecules can occur within the ball structure. This encapsulation creates an endohedral component that is limited from interacting with other molecules which creates potential of control over electronic information of the isolated molecule. Endohedral fullerenes have the potential as serving as the base unit in a quantum computer if control over global alignment is attained. Thus, by using the inherent self-assembling capabilities of some organic materials, ordered endohedral fullerenes can be achieved. This dissertation investigates the ability to use self-assembling strategies to obtain alignment which include ordering within a morphologically controlled copolymer matrix, forming a supramolecular polymer complex with cyclodextrin, and encapsulation within the helical wrap of polymer chains. The ultimate goal is to understand the dynamics that control association and orientation of varying fullerene-based molecules in each strategy in order to maximize control over the final alignment of endohedral elements.

This thesis focuses on developing a new photocoupling surface, base on polyallyamine (PAAm), to increase the efficiency of the photocoupling agent perfluorophenyl azide (PFPA) in the immobilization of nanoparticles, carbohydrates and graphene. Extensive studies have been carried out in our lab on the covalent immobilization of polymers and graphene using PFPA-functionalized surfaces. Here we show that PAAm-based PFPA surface can be used to efficiently immobilize not only graphene and polymers but also nanomaterials and small molecules. This was accomplished by first silanizing silicon wafers with PFPA-silane followed by attaching a thin film of PAAm by UV radiation. Treating the PAAm surface with N-hydroxysuccinimide-derivatized PFPA (PFPA-NHS) yielded the PAAm-PFPA surface. The functionalized surfaces were characterized by ellipsometry (layer thickness), contact angle (surface tension), and ATR-FTIR. The PAAm surface was further characterized by determining the density of amino groups on the surface. The PAAm-PFPA surfaces were subsequently used to covalently immobilize polymers, nanomaterials, carbohydrates and graphene by a simple procedure of coating the molecules or materials on the PAAm-PFPA surface followed by UV irradiation. The resulting surfaces were characterized using ellipsometry, AFM, optical microscopy. The attached carbohydrates were further evaluated using lectins, i.e., carbohydrate-binding proteins.

This study is an investigation of the chemical vapor deposition (CVD) of aluminum and copper on fluoropolymer surfaces and the subsequent interfacial interactions.

Study of Ordered Macroporous Polymer Films by Templating Breath Figures Lulu Song 193 pages Directed by Dr. Mohan Srinivasarao Macroporous films with highly ordered pore patterns have many potential applications. Some examples include microstructured electrode surfaces, photonic band gap materials and filters for cell sorting and bio-interfaces. In this dissertation we discuss a moist-casting method to prepare hexagonally-ordered macroporous films with pore sizes in the range of sub-micron to several microns, where condensed water droplets (breath figures) work as templates. Compared with other templating methods, this one is fast and simple. Well-ordered porous films can be obtained in tens of seconds and the pore size can be easily tailored and dynamically controlled by adjusting the casting conditions. More importantly, there is no need to remove the templates; water droplets just evaporate when the casting processes are finished. This study was carried out with the intention of characterizing the structures, understanding film-formation processes and exploring special properties and possible applications. For the structural characterization, film morphology was studied in detail by normal optical microscopy and laser scanning confocal microscopy (LSCM). Several interesting features have been revealed. Meanwhile, the degree of the order of the porous structures were characterized both in real space via Voronoi diagram and bond-orientational correlation function, and in reciprocal space via Fraunhofer diffraction pattern. To further understand the mechanism, the evaporation of the polymer solutions during the film formation was studied by monitoring their mass over time. Besides, the evolution of breath figures formed on the evaporating polymer solutions was in-situ recorded via a high-speed camera coupled to an optical microscope. Combined with the information on the film structures obtained via LSCM, explanations for some detailed features have been attempted. Wetting property of these films was studied in some detail. The films exhibited lotus effect, mimicking natural non-wetting surfaces. To improve the solvent stability and mechanical properties of the macroporous films for possible applications, crosslinking of the polymer matrix was tried by heating. Crosslinked structures with hexagonal arrays of cone-like air holes were obtained, which might find use as micron-sized beakers for small-quantity analysis.

Lors de ce travail nous avons étudié les modifications de HDPE, PVF, PVDF et PTFE par des plasmas O2 et N2. Nous nous sommes focalisés sur l’effet des ions et des neutres. Nous constatons dans tous les cas une modification de la composition des échantillons, cette modification de composition est accompagnée d’une modification de l’énergie de surface. Les traitements plasma greffent de nouvelles fonctions polaires (oxygénées ou azotées) à la surface des échantillons, responsables de l’augmentation de l’énergie de surface. Le PTFE traité par plasma O2 présente lui un comportement particulier. Il est possible de greffer de faibles quantités d’oxygène à sa surface et d’augmenter faiblement son énergie de surface lors de traitements de courte durée à faibles puissances. Les traitements de plus fortes puissances érodent fortement la surface du PTFE sans y greffer de fonctions oxygénées. Les surfaces obtenues sont extrêmement rugueuses et leur énergie de surface est fortement diminuée, nous obtenons des surfaces de type ultra-hydrophobes.<p>Les résultats obtenus lors des traitements plasma ont été comparés à ceux obtenus dans le cas de traitements par des ions O2+/O+ ou N2+/N+. Ceci nous a permis de mettre en évidence une différence de réactivité des échantillons face aux différents traitements. Cette différence de réactivité nous permet de conclure que les ions ne sont pas l’espèce principale responsable de la modification de nos échantillons lors des traitements plasma.<p>Nous avons également pu mettre en évidence une différence de réactivité entre les différents échantillons. Le HDPE, PVF et PVDF ont des réactivités semblables alors que le PTFE est beaucoup plus résistant aux modifications, nous pensons que ceci est dû à la structure entièrement fluorée du PTFE.<p>Nous avons également étudié la résistance de nos échantillons à l’adsorption de protéines dans le cadre d’une étude sur la biocompatibilité. Nous avons pu montrer que les échantillons de PTFE rendu ultra hydrophobe, après traitement par plasma O2 de haute puissance, présentent une bonne résistance à l’adsorption de protéines. Cette caractéristique est intéressante pour la synthèse de matériaux biocompatibles. <p> / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Untersuchungen zum statistischen Verhalten von Polymerketten auf anziehenden Oberflächen stellen ein spannendes Forschungsgebiet dar aufgrund des Wechselspiels zwischen dem Entropiegewinn bei Ablösung von der einschränkenden Oberfläche und dem Energiegewinn bei der Bildung von Oberflächenkontakten. Für gute und Theta-Lösungen und lange Ketten ist dieses Gebiet recht alt und gut verstanden, doch gibt es immer noch eine Reihe von offenen Fragen, insbesondere zu endlich langen Polymeren, die gerade im Zeitalter zunehmender Miniaturisierung und experimenteller Auflösung Klärung bedürfen, aber nicht zuletzt auch von prinzipiellem Interesse sind. Die vorliegende Arbeit beschäftigt sich mit dem Gleichgewichtsverhalten einer endlich langen Polymerkette in Lösung in der Nähe einer anziehenden Oberfläche. Die Anziehungsstärke wird dabei systematisch variiert und der Einfluss auf die Konformation des Homopolymers studiert. Dies geschieht im kanonischen und im mikrokanonischen Ensemble, die im betrachteten endlichen System nicht identisch sind. Da die Lösungsmittelstärke des selbstwechselwirkenden Polymers durch die Temperatur variiert werden kann, gelang so eine systematische Studie einer Reihe von Konformationsübergängen. Ob das Polymer an einem Ende irreversibel mit der Oberfläche verbunden ist oder sich zu einem gewissen Grad von ihr entfernen kann, spielt für insbesondere den Adsorptionsübergang eine Rolle, die untersucht wird. Anschließend wurde der Einfluss nicht homogener Oberflächenanziehung in Form von attraktiven Streifenpotentialen auf der Oberfläche auf die zuvor beschriebenen Konformationsübergänge studiert. Die Natur der so forcierten Mustererkennung konnte unter anderem abhängig von Streifenbreite und -stärke detailliert beleuchtet und mit dem Verhalten an homogenen Oberflächen in Bezug gesetzt werden. Sämtliche Daten wurden mit Monte-Carlo-Computersimulationen in generalisierten Ensemblen und einem Polymermodell, das atomare Details vernachlässigt, gewonnen.

Indiana University-Purdue University Indianapolis (IUPUI) / It is increasingly recognized that mechanical properties of substrates play a pivotal role in the regulation of cellular fate and function. However, the underlying mechanisms of cellular mechanosensing still remain a topic of open debate. Traditionally, advancements in this field have been made using polymeric substrates of adjustable stiffness with immobilized linkers. While such substrates are well suited to examine cell adhesion and migration in an extracellular matrix environment, they are limited in their ability to replicate the rich dynamics found at cell-cell interfaces. To address this challenge, we recently introduced a linker-functionalized polymer-tethered multi-bilayer stack, in which substrate stiffness can be altered by the degree of bilayer stacking, thus allowing the analysis of cellular mechanosensitivity. Here, we apply this novel biomembrane-mimicking cell substrate design to explore the mechanosensitivity of C2C12 myoblasts in the presence of cell-cell-mimicking N-cadherin linkers. Experiments are presented, which demonstrate a relationship between the degree of bilayer stacking and mechanoresponse of plated cells, such as morphology, cytoskeletal organization, cellular traction forces, and migration speed. Furthermore, we illustrate the dynamic assembly of bilayer-bound N-cadherin linkers underneath cellular adherens junctions. In addition, properties of individual and clustered N-cadherins are examined in the polymer-tethered bilayer system in the absence of plated cells. Alternatively, substrate stiffness can be adjusted by the concentration of lipopolymers in a single polymer-tethered lipid bilayer. On the basis of this alternative cell substrate concept, we also discuss recent results on a linker-functionalized single polymer-tethered bilayer substrate with a lateral gradient in lipopolymer concentration (substrate viscoelasticity). Specifically, we show that the lipopolymer gradient has a notable impact on spreading, cytoskeletal organization, and motility of 3T3 fibroblasts. Two cases are discussed: 1. polymer-tethered bilayers with a sharp boundary between low and high lipopolymer concentration regions and 2. polymer-tethered bilayers with a gradual gradient in lipopolymer concentration.