Metal coordinated polymer nanocomposites have gained great attention due to their superior characteristics. Polymethylmethacyrlate (PMMA) is the most commonly used polymer since it is easily processed. In this study, modified TiO2 nanoparticles prepared by insitu and exsitu methods were embedded into PMMA in order to improve its thermal stability and the effects of TiO2 nanoparticles on thermal characteristics of PMMA were investigated by direct pyrolysis mass spectrometry. The insitu method which is a sol gel method, TiO2/SiO2 nanoparticles were synthesized by mixing titanium(IV) tetraisopropoxide, TTIP, with silane coupling agent, 3-(3-methoxysilyl)methylmetacrylate, MSMA in absolute ethanol. In exsitu method, TiO2 powder was directly mixed with silane coupling reagent. TiO2/SiO2 nanoparticles were embedded into the PMMA by direct mixing resulting in exsitu and insitu TiO2/SiO2/PMMA nanocomposites. The synthesized TiO2/SiO2/PMMA nanocomposites were characterized by TEM, ATR-FT-IR and analyzed for the investigation of their reaction mechanism and thermal characteristics by pyrolysis mass spectroscopy. iv TEM images confirmed the formation of TiO2/SiO2 nanoparticles and TiO2/SiO2/PMMA nanocomposites and indicated that the average particle size of TiO2/SiO2 nanoparticles was around 6 nm whereas average particle size of SiO2/TiO2/PMMA nanocomposites were around 25 nm. The increase in the size of nanoparticles is associated with incorporation of TiO2/SiO2 nanoparticles into PMMA matrix. ATR-FTIR spectrum of 5% TiO2/SiO2/PMMA nanocomposites showed the formation of TiO2/SiO2 nanopartciles clearly. Pyrolysis mass spectrometry analysis revealed that incorporation of TiO2/SiO2 nano- particles into PMMA resulted in higher thermal stability only for low weight percentage insitu TiO2/SiO2/PMMA. At high weight percentages a decrease in thermal stability was detected. On the other hand, in case of exsitu TiO2/SiO2/PMMA, contrary to our expectations a decrease in thermal stability was detected. The decrease in thermal stability was attributed to evolution of methacrylic acid during thermal degradation of silane groups.

This thesis is aimed to understand the role of nanofiller type, nanofiller dispersion, nanofiller geometry, and, presence of reinforcing fibers in flame retardancy of polymer nanocomposites. For this purpose, montmorillonite nanoclays, multi-walled carbon nanotubes, halloysite clay nanotubes and silica nanoparticles were used as nanofillers in polymeric matrices of poly (methyl methacrylate) (PMMA), high-impact polystyrene (HIPS), polylactide (PLA) and polyamide-6 (PA6) containing certain conventional flame retardant additives. Furthermore, the influence of nanofiller and flame retardant additives on fiber/matrix interfacial interactions was studied. Materials were prepared by twin-screw extrusion melt-mixing and ultrasound-assisted solution-mixing techniques. Characterization of nanocomposite morphology was done by X-ray diffraction and transmission electron microscopy. Flame retardancy was investigated by mass loss cone calorimetry, limiting oxygen index measurements and UL94 standard tests. Flame retardancy mechanisms were revealed by characterization of solid fire residues by scanning electron microscopy, transmission electron microscopy, infrared spectroscopy and X-ray diffraction. Thermal degradation and stability was studied using thermogravimetric analysis. Mechanical properties were determined by tension tests and fracture surfaces were observed under scanning electron microscope. Influence of nanofiller type was investigated comparing the behavior of montmorillonite nanoclay and multi-walled carbon nanotube reinforced PMMA nanocomposites containing phosphorous/nitrogenous intumescent flame retardant. Carbon nanotubes hindered the formation of intumescent inorganic phosphate barrier which caused the samples to be exposed to larger effective heat fluxes during combustion. Contrarily, nanoclays physically reinforced the protective barrier without disrupting the intumescent character, thereby allowing for lower heat release and mass loss rates, and increased amounts of residue upon combustion. Influence of nanofiller dispersion was studied comparing nanocomposite and microcomposite morphologies in montmorillonite nanoclay reinforced HIPS containing aluminum hydroxide flame retardant. Relative to microcomposite morphology, reductions in peak heat release rates were doubled along with higher limiting oxygen index and lower burning rates with nanocomposite formation. Improved flame retardancy was attributed to increased amounts of char residue and lower mass loss rates. Nanocomposite formation allowed for the recovery of tensile strength reductions caused by high loading level of the conventional flame retardant additive in polymer matrix. Influence of nanofiller geometry was investigated for phosphorus based intumescent flame-retarded PLA nanocomposites. Fire performance was increased in the order of rod-like (1-D) &lt / spherical (0-D) &lt / &lt / plate-like (2-D) geometries which matched qualitatively with the effective surface area of nanoparticles in the nanocomposite. Well-dispersed plate-like nanoparticles rapidly migrated and accumulated on exposed sample surface resulting in the formation of strong aluminum phosphate/montmorillonite nanocomposite residue. Mechanical properties were increased in the order of 0-D &lt / 1-D &lt / 2-D nanofillers corresponding to the order of their effective aspect ratios in the nanocomposite. Influence of fiber reinforcement was studied for montmorillonite nanoclay containing short-glass fiber-reinforced, phosphorus/nitrogen based flame-retarded PA6 composites. Substitution of a certain fraction of conventional additive with nanofiller significantly reduced peak heat release rate, delayed ignition and improved limiting oxygen index along with maintained UL94 ratings. Improved flame retardancy was ascribed to the formation of a nanostructured carbonaceous boron/aluminum phosphate barrier reinforced by well-dispersed montmorillonite nanolayers. Fiber/matrix interfacial interactions in flame-retarded PA6 and HIPS containing nanoclays were investigated using a micromechanical approach, and it was found that the influence of nanoclay on the interface depends on crystallinity of polymer matrix. While the fiber/matrix interfacial strength is reduced with nanoclay incorporation into amorphous matrix composites, significant interfacial strengthening was imparted by large surface area, well-dispersed clay nanolayers acting as heterogeneous nucleation sites for the semi-crystalline matrix.

Polymer/ceramic nanocomposites benefit by combining high permittivities (r) of metal oxide nanoparticles with high dielectric strength and excellent solution-processability of polymeric hosts. Simple mixing of nanoparticles and polymer generally results in poor quality materials due mainly to the agglomeration of nanoparticles and poor miscibility of nanoparticles in host materials. Surface modification of metal oxide nanoparticles with phosphonic acid-based ligands was found to afford a robust surface modification and improve the processablity and the quality of nanocomposites. The use of phosphonic-acid modified barium titanate (BaTiO₃) nanoparticles in dielectric nanocomposites dramatically improved the stability of the nanoparticle dispersion and the quality of the nanocomposites. Surface modification of BaTiO₃ nanoparticles allowed high quality nanocomposite thin films in ferroelectric polymer hosts such as poly(vinylidene fluoride-co-hexafluoropropylene) with large volume fractions (up to 50 vol. %), which exhibited a remarkable combination of a high permittvity (35 at 1 kHz) and a high breakdown strength (210 V/µm) leading to a maximum energy storage density of 6.1 J/cm³. The effect of nanoparticle volume fractions on the dielectric properties of this nanocomposite system was investigated and compared with theoretical models. At high volume fraction of nanoparticles, the porosity of the nanocomposites was found to have important role in the dielectric performance. A combined effective medium theory and finite difference simulation was used to model the dielectric properties of high volume fraction dielectric nanocomposites with porosity. These results provide a guideline to optimize the volume fractions of nanoparticles for maximum energy density. Nanocomposites based on phosphonic acid-modified BaTiO₃ nanoparticles can also be used as printable high permittivity dielectrics in organic electronics. High volume fractions (up to 37 vol. %) of phosphonic acid-modified BaTiO₃ nanoparticles dispersed in cross-linked poly(4-vinylphenol) allowed solution-processable high permittivity thin films with a large capacitance density (~50 nF/cm²) and a low leakage current (10 8 A/cm²) suitable as a gate insulator in organic field-effect transistors (OFETs). Pentacene-based OFETs using these nanocomposites showed a low threshold voltage (< -2.0 V) and a large on/off current ratio (Ion/off 104 ~ 106) due to the high capacitance density and low leakage current of the gate insulator.

Due to their large internal surface area, microporous materials have been widely used in applications where high surface activity is desired. Example applications are extracellular scaffolds for tissue engineering, porous substrates for catalytic reaction, and permeable media for membrane filtration, etc. To realize these potential applications, various techniques such as TIPS (thermal induced phase separation), particle leaching, and SFF (solid freeform fabrication) were proposed and investigated. Despite of being able to generate microporous for specific applications, these available fabrication techniques have limitations on controlling the inner porous structure and the outer geometry in a cost-effective manner. To address these technical challenges, a systematic study focusing on the generation of microporous structures using co-continuous polymer blend was conducted. Under this topic, five subtopics were explored: 1) generation of gradient porous structures; 2) geometrical confining effect in compression molding of co-continuous polymer blend; 3) microporous composite with high nanoparticle loading; 4) micropatterning of porous structure; 5) simulation strategy for kinetics of co-continuous polymer blend phase coarsening process.

Cellulose nanowhisker (CNW) prepared by acid hydrolysis of softwood Kraft pulp was incorporated as nanofiller in rigid polyurethane (PU) foam synthesis. The density, morphology, chemical structure, mechanical properties and thermal behavior of the products were characterized. The nanocomposites exhibited better performance especially at high CNW¡¯s content which was probably due to the high specific strength and aspect ratio of CNW, the hydrogen bonding and crosslinking between CNW and polymer matrix, a higher crosslinking density compared to the control, and the function of CNW as an insulator and mass transfer insulator. Lignin polyol was synthesized through oxypropylation and used for rigid PU foam preparation. The density, morphology, chemical structure, compressive property and thermal behavior of the product were characterized. Lingin-based rigid PU foam showed improved compressive property compared to its commercial counterpart. Ethanol organosolv lignin-based PU showed a slightly stronger compressive property than Kraft lignin-based PU. The enhancement was primarily attributed to the rigid phenolic structure and the high hydroxyl functionality of lignin. Lignin-based PU generated more char than common PUs which was possibly related to the better flame retardant property. This study provided an alternative way to valorize the two most abundant biopolymers and resulted in relatively environmentally benign rigid PU nanocomposite foam.

Polymer nanocomposite foams have attracted tremendous interests due to their multifunctional properties in addition to the inherited lightweight benefit of being foamed materials. Polymer nanocomposite foams using high performance polymer and bio-degradable polymer with carbon nanotubes were fabricated, and the effects of foam density and pore size on properties were characterized. Electrical conductivity modeling of polymer nanocomposite foams was conducted to investigate the effects of density and pore size. High performance polymer Polyetherimide (PEI) and multi-walled carbon nanotube (MWCNT) nanocomposites and their foams were fabricated using solvent-casting and solid-state foaming under different foaming conditions. Addition of MWCNTs has little effect on the storage modulus of the nanocomposites. High glass transition temperature of PEI matrix was maintained in the PEI/MWCNT nanocomposites and foams. Volume electrical conductivities of the nanocomposite foams beyond the percolation threshold were within the range of electro-dissipative materials according to the ANSI/ESD standard, which indicates that these lightweight materials could be suitable for electro-static dissipation applications with high temperature requirements. Biodegradable Polylactic acid (PLA) and MWCNT nanocomposites and their foams were fabricated using melt-blending and solid-state foaming under different foaming conditions. Addition of MWCNTs increased the storage modulus of PLA/MWCNT composites. By foaming, the glass transition temperature increased. Volume electrical conductivities of foams with MWCNT contents beyond the percolation threshold were again within the range of electro-dissipative materials according to the ANSI/ESD standard. The foams with a saturation pressure of 2 MPa and foaming temperature of 100 °C showed a weight reduction of 90% without the sacrifice of electrical conductivity. This result is promising in terms of multi-functionality and material saving. At a given CNT loading expressed as volume percent, the electrical conductivity increased significantly as porosity increased. A Monte-Carlo simulation model was developed to understand and predict the electrical conductivity of polymer/MWCNT nanocomposite foams. Two different foam morphologies were considered, designated as Case 1: volume expansion without nanotube rearrangement, and Case 2: nanotube aggregation in cell walls. Simulation results from unfoamed nanocomposites and the Case 1 model were validated with experimental data. The results were in good agreement with those from PEI/MWCNT nanocomposites and their foams, which had a similar microstructure as modeled in Case 1. Porosity effects on electrical conductivity were investigated for both Case 1 and Case 2 models. There was no porosity effect on electrical conductivity at a given volume percent CNT loading for Case 1. However, for Case 2 the electrical conductivity increased as porosity increased. Pore size effect was investigated using the Case 2 model. As pore size increased, the electrical conductivity also increased. Electrical conductivity prediction of foamed polymer nanocomposites using FEM was performed. The results obtained from FEM were compared with those from the Monte-Carlo simulation method. Feasibility of using FEM to predict the electrical conductivity of foamed polymer nanocomposites was discussed. FEM was able to predict the electrical conductivity of polymer nanocomposite foams represented by the Case 2 model with various porosities. However, it could not capture the pore size effect in the electrical conductivity prediction. The FEM simulation can be utilized to predict the electrical conductivity of Case 2 foams when the percolation threshold is determined by Monte-Carlo simulation to save the computational time. This has only been verified when the pore size is small in the range of a few micrometers. / text

Lithium-ion batteries are most commonly employed as power sources for portable electronic devices. Limited capacity, high cost, and safety problems associated with the commercially used graphite anode materials are hampering the use of lithium-ion batteries in larger-scale applications such as the electric vehicle. Nanocomposite alloys have shown promise as new anode materials because of their better safety due to higher operating potential, increased energy density, low cost, and straightforward synthesis as compared to graphite. The purpose of this dissertation is to investigate and understand the electrochemical properties of several types of nanocomposite alloys and to assess their viability as replacement anode materials for lithium-ion batteries. Tin and antimony are two elements that are active toward lithium. Accordingly, this dissertation is focused on tin-based and antimony-based nanocomposite alloy materials. Tin and antimony each have larger theoretical capacities than commercially available anodes, but the capacity fades dramatically in the first few cycles when metallic tin or antimony is used as the anode in a lithium-ion battery. This capacity fade is largely due to the agglomeration of particles in the anode material and the formation of a barrier layer between the surface of the anode and the electrolyte. In order to suppress agglomeration, the active anode material can be constrained by an inactive matrix of material that makes up the nanocomposite. By controlling the surface of the particles in the nanocomposite via methods such as the addition of additives to the electrolyte, the detrimental effects of the solid-electrolyte interphase layer (SEI) can be minimized, and the capacity of the material can be maintained. Moreover, the nanocomposite alloys described in this dissertation can be used above the voltage where lithium plating occurs, thereby enhancing the safety of lithium-ion batteries. The alloy anodes in this study are synthesized by high-energy mechanical milling and furnace heating. The materials are characterized by X-ray diffraction, scanning and transmission electron microscopies, and X-ray photoelectron spectroscopy. Electrochemical performances are assessed at various temperatures, potential ranges, and charge rates. The lithiation/delithiation reaction mechanisms for these nanocomposite materials are explored with ex-situ X-ray diffraction. Specifically, three different nanocomposite alloy anode materials have been developed: Mo3Sb7-C, Cu2Sb-Al2O3-C, and Cu6Sn5-TiC-C. Mo3Sb7-C has high gravimetric capacity and involves a reaction mechanism whereby crystalline Mo3Sb7 disappears and is reformed during each cycle. Cu2Sb-Al2O3-C with small particles (2 - 10 nm) of Cu2Sb dispersed in the Al2O3-C matrix is made by a single-step ball milling process. It exhibits long cycle life (+ 500 cycles), and the reversibility of the reaction of Cu2Sb-Al2O3-C with lithium is improved when longer milling times are used for synthesis. The reaction mechanism for Cu2Sb-Al2O3-C appears to be dependent upon the size of the crystalline Cu2Sb particles. The coulombic efficiency of Cu2Sb-Al2O3-C is improved through the addition of 2 % vinylethylene carbonate to the electrolyte. With a high tap density of 2.2 g/cm3, Cu6Sn5-TiC-C exhibits high volumetric capacity. The reversibility of the reaction of Cu6Sn5-TiC-C with lithium is improved when the material is cycled above 0.2 V vs. Li/Li+. / text

Η ανακάλυψη των νανοσωλήνων άνθρακα το 1991 από τον Iijima και οι εκπληκτικές ιδιότητες που βρέθηκε ότι παρουσιάζουν προκάλεσε τεράστιο ενδιαφέρον στην επιστημονική κοινότητα και πολλές ερευνητικές ομάδες ανά τον κόσμο ξεκίνησαν την προσπάθεια να εκμεταλλευτούν τις ιδιότητες αυτές στην ανάπτυξη νέων συνθέτων υλικών και εφαρμογών. Από τις σημαντικότερες εφαρμογές που εξαρχής οι νανοσωλήνες δοκιμάστηκαν, ήταν για την ενίσχυση των μηχανικών, ηλεκτρικών και θερμικών ιδιοτήτων των πολυμερών. Πολύ γρήγορα ωστόσο διαπιστώθηκε ότι η ανάμιξη νανοσωλήνων με πολυμερή είναι εξαιρετικά δύσκολη, με αποτέλεσμα τα νανοσύνθετα υλικά που παράγονταν είτε να έχουν πολύ μικρή ενίσχυση των ιδιοτήτων τους, είτε να παρουσιάζουν ιδιότητες υποδεέστερες από την πολυμερική μήτρα. Το πρόβλημα πηγάζει από την σχεδόν μονοδιάστατη δομή των νανοσωλήνων, με αποτέλεσμα να έχουν την τάση να συσσωματώνονται και έτσι να μην διασπείρονται ομογενώς σε μεγάλες συγκεντρώσεις μέσα στην πολυμερική μήτρα με τις υπάρχουσες τεχνικές μορφοποίησης των πολυμερών. Τα παραγόμενα νανοσύνθετα υλικά είναι χαμηλής περιεκτικότητας σε νανοσωλήνες άνθρακα και παρουσιάζουν φτωχές ιδιότητες καθώς, εντέλει, τα συσσωματώματα δρουν ως ατέλειες, και όχι ως ενισχυτικά μέσα. Η παρούσα εργασία φιλοδοξεί να δώσει μια κατεύθυνση προς τη λύση του παραπάνω προβλήματος, της ανομοιογενούς δηλαδή διασποράς νανοσωλήνων σε πολυμερικές μήτρες και να παράγει ένα νανοσύνθετο υλικό με υψηλή περιεκτικότητα σε νανοσωλήνες και βελτιωμένες ιδιότητες σε σχέση με την πολυμερική μήτρα. Η βασική ιδέα είναι η παρασκευή ξηρών υμενίων νανοσωλήνων άνθρακα (τα λεγόμενα buckypapers), αποτελούμενων δηλαδή από δίκτυα νανοσωλήνων άνθρακα περιπλεγμένων μεταξύ τους και κατόπιν η διαβροχή τους από το πολυμερές. Η μέθοδος αυτή έχει το μεγάλο πλεονέκτημα ότι τα υμένια παρουσιάζουν πολύ υψηλό βαθμό ομοιογένειας, η οποία και διατηρείται και μετά την εισροή του πολυμερούς. Το αποτέλεσμα είναι τα παραγόμενα νανοσύνθετα να είναι ομογενή και υψηλής περιεκτικότητας σε νανοσωλήνες. Πιο συγκεκριμένα, στην παρούσα εργασία παρασκευάστηκαν νανοσύνθετα υλικά εποξειδικής μήτρας με πολυφλοιικούς νανοσωλήνες άνθρακα ως ενισχυτική φάση σε μορφή υμενίων. Η παρασκευή τους έγινε σε τέσσερα στάδια. Αρχικά οι νανοσωλήνες τροποποιήθηκαν επιφανειακά με δύο διαφορετικές χημικές μεθόδους (οξείδωση-εποξείδωση), ώστε να αποφευχθεί η συσσωμάτωσή τους και για να επιτευχθεί καλύτερη χημική συνάφεια με την εποξειδική ρητίνη. Το δεύτερο στάδιο περιελάμβανε την παρασκευή των υμενίων νανοσωλήνων άνθρακα με ή χωρίς οξείδια του γραφενίου, δηλαδή σχηματίστηκαν μακροδομές νανοσωλήνων, οι οποίες και αποτέλεσαν την ενισχυτική φάση για τα νανοσύνθετα υλικά. Στο τρίτο στάδιο παρασκευάστηκαν προεμπτισμένα με ρητίνη υμένια νανοσωλήνων άνθρακα (prepregs), με την εμβάπτιση των υμενίων σε εποξειδική ρητίνη και την κατάψυξή τους, ενώ κατά το τέταρτο στάδιο πραγματοποιήθηκε η παραγωγή των νανοσυνθέτων από τα προεμποτισμένα υμένια με χρήση αυτόκλειστου φούρνου. Στη συνέχεια τα υμένια και τα νανοσύνθετα που παρασκευάστηκαν χαρακτηρίσθηκαν ώστε να μελετηθεί η δομή και οι ιδιότητες των υλικών αυτών. Οι νανοσωλήνες χαρακτηρίσθηκαν θερμικά με θερμοσταθμική ανάλυση και δομικά με φωτοηλεκτρονιακή φασματοσκοπία ακτίνων Χ και ηλεκτρονική μικροσκοπία. Η δομή των υμενίων μελετήθηκε με ποροσιμετρία υδραργύρου και ηλεκτρονική μικροσκοπία. Μηχανικά, τα υμένια δοκιμάστηκαν με εφελκυσμό και μελετήθηκε η μικρομηχανική τους με φασματοσκοπία Raman. Τα νανοσύνθετα που παρασκευάστηκαν μελετήθηκαν δομικά με ηλεκτρονική μικροσκοπία σάρωσης και προσδιορίστηκαν οι μηχανικές, ηλεκτρικές και θερμικές τους ιδιότητες. Η μελέτη των πειραματικών αποτελεσμάτων έδειξε ότι η χημική τροποποίηση της επιφάνειας των νανοσωλήνων επηρεάζει τις ιδιότητες των υμενίων όπως το πορώδες, το οποίο με τη σειρά του επηρεάζει τις ιδιότητες των παραγόμενων νανοσυνθέτων. Υπάρχει δηλαδή άμεση συσχέτιση δομής-ιδιοτήτων μεταξύ των νανοσωλήνων, των υμενίων και των νανοσυνθέτων. Τα παραγόμενα νανοσύνθετα υλικά εμφανίζουν ενισχυμένες μηχανικές, ηλεκτρικές και θερμικές ιδιότητες οι οποίες μπορούν να φανούν χρήσιμες για την ανάπτυξη νέων εφαρμογών. / The discovery of carbon nanotubes in 1991 by Iijima and their explicit properties has attracted for many years the scientific interest and many research groups around the world have started an effort to take advantage of these properties for the development of new materials and applications. Carbon nanotubes have been used mostly for the reinforcement of the mechanical, electrical and thermal properties of polymers, but very soon it was found that the dispersion of these nanomaterials into polymers is very difficult and the produced nanocomposites presented negligible reinforcement of their properties, or even inferior than the properties of polymeric matrices. The problem arises from the quasi-one dimensional structure of the nanotubes, leading them to form bundles and preventing them to be dispersed homogenous and in large amounts by the current polymers processing. The aim of the current thesis is to solve the problem of the inhomogeneous dispersion of nanotubes into polymers and to fabricate a high volume fraction nanocomposite material of carbon nanotubes with improved properties compared to the matrix. The basic idea is the formation of thin sheets of randomly entangled nanotubes, the so-called buckypapers, and the impregnation of them by the matrix. The main advantage of this method is that buckypapers are homogenous materials and this homogeneity remains after the infusion of the polymer. More specifically, at this work polymeric nanocomposite materials with carbon nanotubes as reinforcement at the form of buckypapers were produced. The production involved four steps. Firstly, the surface of the nanotubes was modified by two different chemical processed (oxidation-epoxidation) to prevent the formation of bundles and to achieve a better chemical compatibility with the matrix. At a second stage buckypapers were prepared to consist the reinforcement material for nanocomposites. The third step was the soaking of buckypapers into an epoxy resin and the refrigeration to form prepregs and on the final step prepregs were place on an autoclave oven for the curing and the production of the nanocomposites. The nanotubes and the produced buckypapers and nanocomposites characterized to study their structure and properties. Nanotubes characterized by thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Buckypapers structure was studied by porosity measurements and SEM, and their mechanical properties by tensile experiments and Raman spectroscopy. Nanocomposites were studied by SEM and their mechanical, electrical and thermal properties were determined. The study of the experimental results showed that the chemical modification of the nanotubes affects the properties of the buckypapers such as the porosity, which also influences the properties of the subsequent nanocomposites. So there is a strong structure-properties correlation between nanotubes, buckypapers and nanocomposites. The produced nanocomposites presented improved mechanical, electrical and thermal properties that may be useful for the development of new applications.

For several decades, the field of magneto-optics (MO) has demonstrated applications that have impact on every day applications such as in optical data storage, magnetic field sensing, crucial for magnetoencephalography and magnetocardiography; and compact and efficient optical isolators, among others. In the past, many of these applications and the devices designed for them have heavily relied on inorganic materials. Organic materials with a high MO response represent an interesting alternative to the inorganic equivalent by not only being a more cost efficient solution, but also by allowing the user to modify a number of variables to control and optimize the MO performance depending on the application and level of performance desired. In this dissertation I discuss the MO properties of novel organic materials, starting with polythiophene, which has been of interest due to the strong relationship between its high MO performance and its lamellar structure and regioregularity. I will also be discussing another material system that provides several degrees of MO tunability: magnetite based nanocomposites. A unique and novel synthetic approach described in this dissertation yields both highly transparent and MO responsive polymer films. I will be describing a systematic approach that indicates a strong influence of the size of the nanoparticle as well as the nanoparticle concentration in the MO performance of the bulk polymer, while maintaining high optical quality with minimal scattering and absorption in the visible and near infrared. Finally, I will be discussing the implementation of both a magnetite nanocomposite and a cobalt ferrite based nanocomposite in a free space magnetic field system and demonstrate the proof-of-principle operation of a sensing system.

The structure-property relationships of epoxy nanocomposites with inorganic layer-structure nanofillers have been studied to obtain the fundamental understanding of the role of nanofillers and the physics of polymer nanocomposites in this dissertation. Several polymer nanocomposite systems with modified montmorillonite (MMT) or α-zirconium phosphate (ZrP) nanofillers were prepared with epoxy matrices of different ductility and properties. The successful nanofiller's exfoliations were confirmed with X-ray diffraction and transmision electronic microscopy (TEM). Dynamic mechanical analysis (DMA) on the prepared epoxy nanocomposites revealed the significant increase in rubbery plateau moduli of the epoxy nanocomposite systems above Tg, as high as 4.5 times, and tensile test results showed improved modulus by the nanofiller addition, while the fracture toughenss was not affected or slightly decreased by nanofillers. The brittle epoxy nanocomposite systems were toughened with core shell rubber (CSR) particles and showed remarkable increase in fracture toughness (KIC) value up to 270%. The CSR toughening is more effective at ductile matrices, and TEM observation indicates that major toughening mechanisms induced by the CSR addition involve a large scale CSR cavitation, followed by massive shear deformation of the matrix.