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This thesis discusses the full scope of a project exploring the physics of hierarchical clusters of interacting nanomagnets. These clusters may be relevant for novel applications such as multilevel data storage devices. The work can be grouped into three main activities: micromagnetic simulation, fabrication and characterization of proof-ofconcept prototype devices, and efforts to scale down the structures by creating the hierarchical structures with the aid of diblock copolymer self assembly. Theoretical micromagnetic studies and simulations based on Landau-Lifshitz- Gilbert (LLG) equation were conducted on nanoscale single domain magnetic entities. For the simulated nanomagnet clusters with perpendicular uniaxial anisotropy, the simulation showed the switching field distributions, the stability of the magnetostatic states with distinctive total cluster perpendicular moments, and the stepwise magnetic switching curves. For simulated nanomagnet clusters with in-plane shape anisotropy, the simulation showed the stepwise switching behaviors governed by thermal agitation and cluster configurations. Proof-of-concept cluster devices with three interacting Co nanomagnets were fabricated by e-beam lithography (EBL) and pulse-reverse electrochemical deposition (PRECD). EBL patterning on a suspended 100 nm SiN membrane showed improved lateral lithography resolution to 30 nm. The Co nanomagnets deposited using the PRECD method showed perpendicular anisotropy. The switching experiments with external applied fields were able to switch the Co nanomagnets through the four magnetostatic states with distinctive total perpendicular cluster magnetization, and proved the feasibility of multilevel data storage devices based on the cluster concept. Shrinking the structures size was experimented by the aid of diblock copolymer. Thick poly(styrene)-b-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer templates aligned with external electrical field were used to fabricate long Ni/Fe magnetic nanowire array, dominant shape anisotropy was observed and compared to the result from previously reported Co nanowire array with strong crystalline anisotropy. Guided diblock copolymer poly(styrene)-b-poly(4-vinyl pyridine) (PS-b-P4VP) self assembly was performed to generate clustered microdomains. Direct e-beam patterning on PS-b-P4VP thin film showed precise and arbitrary patterning on the lateral ordering of the self assembly. Graphoepitaxy of self-assembled PS-b-P4VP copolymers on isolated SiN triangular plateaus successfully resulted in the exact clusters of three microdomains. Theoretical consideration and system modeling based on the micellar configuration of the microdomains were done, and the distribution of the cluster’s size and number of elements were explained qualitatively.

Interfacial features of polymers are a complex, fascinating topic, and industrially very important. There is clearly a need to understand interactions between polymer layers as they can be used for controlling surface properties, colloidal stability and lubrication. The aim of my Ph.D study was to investigate fundamental phenomena of polymers at interfaces, covering adsorption, interactions between polymer layers and surfactants, surface forces and friction between adsorbed layers. A branched brush layer with high water content was formed on silica surfaces by a diblock copolymer, (METAC)m-b-(PEO45MEMA)n, via physisorption. The adsorption properties were determined using several complementary methods. Interactions between pre-adsorbed branched brush layers and the anionic surfactant SDS were investigated as well. Surface forces and friction between polymer layers in aqueous media were investigated by employing the Atomic Force Microscopy (AFM) colloidal probe technique. Friction forces between the surfaces coated by (METAC)m-b-(PEO45MEMA)n in water are characterized by a low friction coefficient. Further, the layers remain intact under high load and shear, and no destruction of the layer was noted even under the highest pressure employed, about 50 MPa. Interactions between polymer layers formed by a temperature responsive diblock copolymer, PIPOZ60-b-PAMPTMA17 (phase transition temperature of 46.1 °C), was investigated in the temperature interval 25-50 °C by using the AFM colloidal probe technique. Friction between the layers increases with increasing temperature (25-45 °C), while at 50 °C friction was found to be slightly lower than that at 45 °C. We suggest that this is due to decreased energy dissipation caused by PIPOZ chains crystallizing in water above the phase transition temperature. The structure of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) bilayers was determined by X-ray reflectometry. Surface forces and friction between DPPC bilayer-coated silica surfaces were measured utilizing the AFM colloidal probe technique. Our study showed that DPPC bilayers are able to provide low friction forces both in the gel (below ≈ 41°C) and in the liquid crystalline state (above ≈ 41°C). However, the load bearing capacity is lower in the gel state. This is attributed to a higher rigidity and lower self-healing capacity of the DPPC bilayer in the gel state. Friction forces in single asperity contact acting between a micro-patterned silicon surface and an AFM tip was measured in air. We found that both nanoscale surface heterogeneities and the µm-sized depressions affect friction forces, and considerable reproducible variations were found along a particular scan line. Nevertheless, Amontons’ first rule described average friction forces reasonably well. Amontons’ third rule and Euler’s rule were found to be less applicable to our system. / <p>QC 20141209</p>

Non-oxide porous ceramics exhibit many unique and superior properties, such as better high-temperature stability, improved chemical inertness/corrosive resistance, as well as wide band-gap semiconducting behavior, which lead to numerous potential applications in catalysis, high temperature electronic and photonic devices, and micro-electromechanical systems. Currently, most mesoporous non-oxide ceramics (e.g. SiC) are formed by two-step templating methods, which are hard to adjust the pore sizes, and require a harmful etching step or a high temperature treatment to remove the templates. In this dissertation, we report a novel technique for synthesizing hierarchically mesoporous non-oxide SiC ceramic from a block copolymer precursor. The copolymer precursors with vairing block length were synthesized by reversible addition fragmentation chain transfer polymerization. The block copolymers self-assemble into nano-scaled micelles with a core-shell structure in toluene. With different operation processes, hollow SiC nanospheres and bulk mesoporous SiC ceramics were synthesized after the subsequent pyrolysis of precorsur micelles. The resultant SiC ceramics have potential applications in catalysis, solar cells, separation, and purification processes.The polymer synthesis and pyrolysis process will investigated by NMR, FTIR, GPC, TEM, and TGA/DSC. The morphology and structure of synthesised SiC hollow spheres and mesoporous ceramics were analyzed by SEM, TGA/DSC and BET/BJH analysis. Besides forming core shell micelles in selective solvent Toluene, we found that PVSZ-b-PS could also exhibit this property in the air water interface. By inducing the Langmuir-Blodgett deposition, a precursor monolayer with homogeously distributed povinylsilazane particles deposited on silicon wafer synthesized by spreading the diblock copolymer PVSZ-b-PS in the air water interface. After the pyrolysis process, orderly arranging SiC nano particles formed from the polymer precursor monolayer doped on the surface of silicon wafer, which shows great potential as an optoelectronic material. The deposition process and the relationship between compress pressure and monolayer morphology were studies, and the structure of monolayer and SiC dots were investigated by AFM, SEM.

Two diverse projects illustrate the application of various materials characterization techniques to investigate the structure and properties of nanostructured functional materials formed in both bulk as well as in solutions. In the first project, ordered magnetic nanostructures were formed within polymer matrix by novel metallopolymers. The novel metal-functionalized block copolymers (BCPs) enabled the confinement of cobalt metal ions within nanostructured BCP domains, which upon simple heat treatment resulted in room temperature ferromagnetic (RTFM) materials. On the contrary, cobalt functionalized homopolymer having similar chemical structure and higher loading of metal-ion are unstructured and exhibited superparamagnetic (SPM) behavior at room temperature. Based on a series of detailed investigations, using various materials characterization techniques, it was hypothesized that the SPM cobalt particles within BCP microdomains exhibited a collective behavior due to increased dipolar interactions between them under the nanoconfinement of cylindrical domains in BCP, resulting in RTFM behavior. On contrary, the same SPM cobalt particles formed within homopolymer, without any confinement exhibited SPM behavior either due to lack of interactions or random interactions between them. To further support this hypothesis, a series of BCPs were prepared in which the BCP morphology was varied between the cylindrical, lamellar, and inverted cylindrical phases and their magnetic properties were compared. All these BCPs, which are nanostructured, exhibited RTFM behavior, further supporting the proposed hypothesis. Different dimensionality or degree of nanoconfinement in BCP morphologies affected the magnetization reversal processes in these BCPs, yielding different macroscopic magnetic properties. Most strongly constrained cylindrical morphology has shown best magnetic properties (highest coercivity) among other BCP morphologies. Inverted cylindrical morphology, in which a 3-D matrix is confined between the non-magnetic cylinders, had second highest and lamellar morphology with least confinement among BCPs, exhibited lowest coercivity. The proposed hypothesis was further tested by systematically varying the dipolar interactions between the SPM cobalt nanoparticles by reducing the density of cobalt within the cylindrical domains and varying the dimensions of the cylindrical domains (i.e. diameter). A series of novel ferrocene-cobalt containing block copolymers were developed and cobalt density within the cylindrical domains of BCP was varied by changing the chemical composition of the metal functionalized block. Further, the diameter of the cylindrical domains was varied by varying the molecular weight of the cobalt-containing BCPs. These studies allowed us to understand the fundamental correlations between the self-assembled nanostructures and their macroscopic magnetic properties. In the second part of the thesis, a novel amphiphilic block copolymer (ABC), composed of a hydrophilic zwitterionic block and a hydrophobic PS block, was synthesized by ROMP. The formation of zwitterionic vesicles in an ionic liquid, as well as in PBS buffer, was confirmed by TEM and DLS characterization. The dispersion of vesicles within ionic liquid enabled the usage of conventional, room temperature TEM to visualize them in their solution state. This technique of materials characterization could be extended for the visualization of other hydrophilic soft matter.

The main objective of this thesis work was to gain understanding of the layer properties and polymer structures that were able to aid lubrication in aqueous media. To this end, three types of polyelectrolytes: a diblock copolymer, a train-of-brushes and two brush-with-anchor mucins have been utilized. Their lubrication ability in the boundary lubrication regime has been examined by Atomic Force Microscopy with colloidal probe. The interfacial behavior of the thermoresponsive diblock copolymer, PIPOZ60-b-PAMPTAM17,on silica was studied in the temperature interval 25-50 ˚C. The main finding is that adsorption hysteresis, due to the presence of trapped states, is important when the adsorbed layers are in contact with a dilute polymer solution. The importance of trapped states was also demonstrated in the measured friction forces, where significantly lower friction forces, at a given temperature, were encountered on cooling than on the preceding heating stage, which was attributed to increased adsorbed amount. On the heating stage the friction force decreased with increasing temperature despite the worsening of the solvent condition, and the opposite trend was observed when using pre-adsorbed layers (constant adsorbed amount) as a consequence of increased segment-segment attraction. The second part of the studies was devoted to the interfacial properties of mucins on PMMA. The strong affinity provided by the anchoring group of C-PSLex and C-P55 together with their more extended layer structure contribute to the superior lubrication of PMMA compared to BSM up to pressures of 8-9 MPa. This is a result of minor bridging and lateral motion of molecules along the surface during shearing. We further studied the influence of glycosylation on interfacial properties of mucin by utilizing the highly purified mucins, C-P55 and C-PSLex. Our data suggest that the longer and more branched carbohydrate side chains on C-PSLex provide lower interpenetration and better hydration lubrication at low loads compared to the shorter carbohydrate chains on C-P55. However, the longer carbohydrates appear to counteract disentanglement less efficiently, giving rise to a higher friction force at high loads. / <p>QC 20170407</p>

Nous avons étudié l'utilisation du phénomène de ségrégation de surface afin de fonctionnaliser des matériaux polystyrène (PS). L'incorporation d'un additif copolymère à blocs est réalisée dans une matrice d'homopolymère de polystyrène sous forme de film ou de particule. Quand les mélanges sont recuits dans un environnement humide le copolymère amphiphile migre à la surface pour réduire la tension de surface du matériau. Nous avons synthétisé au laboratoire trois copolymères à blocs de nature chimique différente: le PS-b-PAA (polyacide acrylique), le PS-b-PGA (polyacide glutamique) et le PS-b-PDMA (polyméthacrylate de diméthylaminoéthyle). Ces copolymères nous permettrons d’accéder à des comportements superficiels variés. Les films sont réalisés par spin-coating et les particules par polymérisation par précipitation. Ces matériaux sont ensuite caractérisés par mesure de l'angle de contact, par XPS, AFM, etc…, afin de déterminer leur fonctionnalité et leur structuration en surface. / We describe the use of surface segregation to functionalize the surface of polymeric materials. The incorporation of an additive (amphiphilic block copolymer) in a homopolymer host initially leads to its homogeneous distribution within the matrix. When annealed, directed by the decrease of the surface free energy, the surface is enriched on the additive. In our laboratory, polystyrene thin films and particles were functionalized by following this approach. We employed amphiphilic block copolymers composed of one PS block to compatibilize with the homopolymer matrix, and a second block which will bring the desired function at the surface. Thus, PS-b-poly(acrylic acid), PS-b-poly(L-glutamic acid) or PS-b-poly(L-Lysine) afford pH sensitivity and PS-b-poly(dimethylaminoethyl methacrylate) gives pH and thermo sensitivity. Contact angle measurements, X-ray photoelectron spectroscopy, atomic force microscopy, zeta potential measurement or scanning electron microscopy were carried out to characterize the materials and their responsive behavior.

Dans un contexte de miniaturisation à l’extrème des composants électroniques, les copolymères àblocs apportent une réponse technologique alternative aux procédés conventionnels destructuration des matériaux par lithographie. Parmi les défis à relever, l’obtention de systèmes decopolymères suffisamment résolus demeure un élément essentiel pour que cette technique puisseoffrir une réelle alternative pour la lithographie sub-20 nm. Nous montrons au travers del’exemple du maltoheptaose-b-polystyène (MH-b-PS) que les copolymères biosourcés ont lacapacité d’atteindre une résolution sub-10 nm grâce à l’association d’un bloc hydrophile(l’oligosaccharide) et d’un bloc hydrophobe (le polystyrène). Les études par AFM, SAXS etGISAXS réalisées sur les films de MH-b-PS ont permis de montrer que le recuit sous vapeur desolvant est plus efficace que le recuit thermique pour organiser ce type de copolymère, composéd’un bloc sensible à la dégradation thermique. Ensuite, une étude inédite du recuit sous vapeur desolvant par QCM-D (Micro-balance à quartz avec mesure de dissipation) a été présentée et adémontré la capacité de cette technique à caractériser la quantité de solvant absorbée par le filmau cours du traitement ainsi que l’évolution de la viscoélasticité du film permettant ainsi d’obtenirdes informations indispensables à la compréhension du mode d’action du recuit sous vapeur desolvant. Finalement, l’étude en solution de ce copolymère ainsi que l’impact de la longueur deschaines des deux blocs sur la morphologie des films auto-organisés permettra de mieuxcomprendre à l’échelle de la chaine de polymère le comportement spécifique du MH-b-PS. / The constant desire of size reduction in nanoelectronic leads to develop processes, able to patternmaterials at the sub-10 nm scale. In this context, self-assembling block copolymers are promisingmaterials offering an alternative method to conventional lithography techniques. Currently, one ofthe major challenges in this field is to find copolymers that could address sub-10 nm pattern sizein order to provide a competitive process. In this thesis, we studied the maltoheptaose-bpolystyrene(MH-b-PS) and we showed that these kinds of sugar-based copolymers are able toself-assemble on a sub-10 nm scale thanks to the combination of a hydrophilic block (sugar) and ahydrophobic block (polystyrene). The AFM, SAXS and GISAXS studies realized on the MH-b-PS films showed that for this kind of copolymer whose one of the block is easily degraded withtemperature, the solvent annealing is more efficient than the thermal annealing to self-assemblethe copolymer. Then, an original study of the solvent annealing by QCM-D (Quartz crystalmicrobalance with dissipation monitoring) evidenced that this technique is able to characterize theviscoelasticity of the film and the amount of solvent absorbed by the copolymer during the solventtreatment. These useful measurements allowed to improve our understanding of the poorly knownsolvent annealing mechanism. To finish, we performed a study of the copolymer in solution and astudy of the impact of the chain length on the morphology of the film and were able to highlightthe specific behavior of this copolymer at the level of the polymer chain.

<p>The phase behavior of AB diblock copolymers mixed with C homopolymers (AB/C), in which A and C are capable of forming hydrogen-bonds, is examined using self-consistent field theory. The study focuses on the modeling of hydrogen-bonding in polymers. Specifically, we examine two models for the formation of hydrogen-bonds between polymer chains. The first commonly used model assumes a large attractive interaction parameter between the A/C monomers. This model reproduces correct phase transition sequences as compared with experiments, but it fails to correctly describe the change of lamellar spacing induced by the addition of the C homopolymers. The second model is based on the fact that hydrogen-bonding leads to A/C complexation. We show that the interpolymer complexation model predicts correctly the order-order phase transition sequences and the decrease of lamellar spacing for strong hydrogen-bonding. Our analysis demonstrates that hydrogen-bonding of polymers should be modeled by interpolymer complexation.</p> / Master of Science (MSc)

Στην εργασία αυτή μελετήθηκε o ρυθμός ροής υδατικών διαλυμάτων, σε διάφορα pH περιβάλλοντος, διαμέσου ενός νανοπορώδους υλικού τροποποιημένου με πολυμερικές ψήκτρες. Ειδικότερα, ερευνήθηκε το σύστημα του σύνθετου υλικού πορώδους ανοδικής αλουμίνας με πολυμερικές ψήκτρες του γραμμικού δισυσταδικού συμπολυμερούς πολύ(Ισοπρένιου)–b–πολυ(Ακρυλικού Οξέους) (ΙΑΟ). Η προσρόφηση καθώς και η κινητική προσρόφησης του IAO στο νανοπορώδες υλικό διερευνήθηκε κυρίως μέσω τεχνικών δονητικής φασματοσκοπίας. Πιο συγκεκριμένα με τεχνικές υπερύθρου μετασχηματισμού κατά Φουριέ (Fourier Transform Infrared Spectroscopy ή FT-IR), εγγύ υπερύθρου (N-IR) και Αποσβεννύμενη Ολική Ανάκλαση στο μέσο υπέρυθρο (ATR-IR). Ακόμη, με σκοπό την ποσοτικοποίηση της προσροφημένης ποσότητας του ΙΑΟ εφαρμόστηκε η τεχνική της θερμοσταθμικής ανάλυσης (TGA). Τέλος, για την απόκτηση μιας λεπτομερούς εικόνας σχετικά με τη δομή του σύνθετου νανο-πορώδους υλικού τα δείγματα χαρακτηρίστηκαν και με ηλεκτρονική μικροσκοπία (SEM/EDS). / In the present study the flow rate of aqueous solutions of different pH values through a nanoporous material functionalized with polymeric brushes was investigated using spectroscopic and thermogravimetric methods. In particular, the system under study was a composite material of porous anodic alumina with polymeric brushes of the diblock copolymer poly(Isoprene)–b–poly(Acrylic Acid) (IAO). The adsorption and adsorption kinetics of the IAO onto nanoporous alumina were explored mainly through techniques of vibrational spectroscopy. More specifically Fourier Transformed Infrared Spectroscopy (FT-IR), Near Infrared (N-IR) and Attenuated Total Reflectance (ATR-IR) were employed for this purpose. Moreover, for the quantification of the adsorbed amount of IAO, thermogravimetric analysis was applied (TGA). Finally, to obtain a comprehensive picture of the structure of the nanoporous composite materials used in this study, samples were additionally characterized by electron microscopy (SEM/EDS).