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With many processing advantages, electrophoretic deposition (EPD) has been chosen as the fabrication technique for inorganic-organic nanocomposites. However, before the EPD process, avoiding the particles agglomeration is considered a necessary perquisite for the success of fabrication. In this research, two different liquid-liquid extraction methods, one is one-step and the other is two-step, were developed to solve the agglomeration problem of inorganic particles. The adsorption mechanisms of the extractors and extraction mechanisms were investigated during this work. The strong adsorptions provided by –OH groups of the extractors and further Schiff base reaction allowed for the process of extraction. In the fabrication, polyelectrolytes acted as the film forming and charging agents. Relatively stable suspensions with extracted inorganic particles were prepared for the EPD of inorganic-organic nanocomposites. The thickness of deposited films is proportional to the concentration of the suspension and deposition time. With the addition of flame retardant inorganic particles, the prepared nanocomposite films showed an enhanced flame retardant performance. / Thesis / Master of Applied Science (MASc)

Yes / Polymer nanocomposites are usually characterized using various methods, such as small angle X-ray diffraction (XRD) or transmission electron microscopy, to gain insights into the morphology of the material. The disadvantages of these common characterization methods are that they are expensive and time consuming in terms of sample preparation and testing. In this work, near infrared spectroscopy (NIR) spectroscopy is used to characterize nanocomposites produced using a unique twin-screw mini-mixer, which is able to replicate, at ~25 g scale, the same mixing quality as in larger scale twin screw extruders. We correlated the results of X-ray diffraction, transmission electron microscopy, G′ and G″ from rotational rheology, Young’s modulus, and tensile strength with those of NIR spectroscopy. Our work has demonstrated that NIR-technology is suitable for quantitative characterization of such properties. Furthermore, the results are very promising regarding the fact that the NIR probe can be installed in a nanocomposite-processing twin screw extruder to measure inline and in real time, and could be used to help optimize the compounding process for increased quality, consistency, and enhanced product properties

No / The performance of cement-based materials can be controlled and tailored by adjusting the characteristics of reinforced nano inclusions. Therefore, the lateral size effect of graphene on the nano/micro-structures of ultra-high performance concrete (UHPC) was explored, and then the mechanical properties were investigated to analyze the structure–property correlation of composites in this paper. The test results show that due to nucleation site effect and the formation of core–shell elements, incorporating graphene with lateral size of > 50 µm improves the polymerization degree and mean molecule chain length of C-S-H gel by 242.6% and 56.3%, respectively. Meanwhile, the porosity and average pore volume of composites is reduced by 41.4% and 43.4%. Furthermore, graphene can effectively inhibit the initiation and propagation of cracks by crack-bridging, crack-deflection, pinning and being pulled-out effect, and the wrinkling characteristic is conductive to the enhancement of pinning effect. These improvements on nano- and micro- structures result in that the compressive strength, compressive toughness and three-point bending modulus of UHPC are increased by 43.5%, 95.7% and 39.1%, respectively, when graphene with lateral size of > 50 µm and dosage of 0.5% is added. Compared to graphene with lateral size of > 50 µm, graphene with average lateral size of 10 µm has less folds and larger effective size, then reducing the distance between core–shell elements. Hence, the addition of graphene with average lateral size of 10 µm leads to 21.1% reduction for Ca(OH)2 crystal orientation index, as well as 30.0% increase for three-point bending strength. It can be, therefore, concluded that the lateral size of graphene obviously influences the nano/micro-structures of UHPC, thus leading to the significantly different reinforcing effects of graphene on mechanical behaviors of UHPC.

This work has been concerned with the dimensional stability and the structure-property relationships of thermoplastics reinforced with particulate and fiber fillers. The first part of this study was concerned with ascertaining the main causes of warpage observed for injection-molded thermoplastics reinforced with high aspect ratio fibers. Typically, warpage in injection-molded fiber reinforced thermoplastics is primarily attributed to residual thermal stresses associated with shrinkage and thermal contraction of the parts. Therefore, it is assumed that flow-induced stresses generated during mold filling do not play a significant role in the warpage. The warpage of PP composites reinforced with TLCP fibers was found to increase with an increase in fiber loading. The shrinkage and the thermal expansion of the TLCP/PP composites and, hence, the thermally induced stresses decreased with an increase in fiber loading while the flow-induced stresses increased. The increase in the flow-induced stresses was attributed to an inhibition of stress relaxation and greater generation of orientation of the polymer chains with an increase in fiber loading. Therefore, it was found that in order to accurately predict the warpage of fiber reinforced thermoplastics, the flow-induced residual stresses must be accounted for. The second part of this work was concerned with minimizing the particle loading of reinforced PC/PBT composites while maintaining the stiffness, i.e. modulus, and the dimensional stability of injection molded flat panels. This was accomplished by using high aspect ratio (≈100-150) nano-clays as opposed to micron-size talc (≈5-10). It was found that by using nano-clays surface modified with a quaternary ammonium salt that contained two hydroxyl groups as opposed to fine talc particles, the level of particle reinforcement could be reduced from 6 to 1 wt% without sacrificing the modulus of the reinforced PC/PBT composites. Further benefits included a 26% increase in flexural strength, 77% increase in the tensile toughness and 3% reduction in the density of the reinforced PC/PBT composites. An increase in the modulus and tensile toughness was observed even though there was evidence of loss in molecular weight of the PC/PBT matrix, which was supported by the rheological behavior of the composites. / Ph. D.

The objective of this study was to determine if the method of incorporation of a silicate layered nanoclay into a polymer matrix can affect the barrier properties of the pristine polymer in order to decrease the transport of volatile organic compounds (VOC) in indoor air. Building materials are a primary source for VOCs. These emissions are a probable cause of acute health effects and discomfort among occupants and are known to diminish productivity. The predicted concentrations of several of the VOCs emitted by structural insulated panels (SIP) are of concern with respect to health and comfort of occupants. The main issue related to the barrier membranes is the dispersion properties of the nanoclays in the polymer matrix, and the generation of a tortuous pathway that will decrease gas permeation. The tortuous pathway is created by a nanoclay filler, whose ideal exfoliated structure has high surface area, and high aspect ratio. By choosing the appropriate surfactants, the nanoclays can be modified to allow improved molecular interactions between the nanoclay and the polymer matrix. Several studies were performed in order to evaluate the dispersion properties of the nanoclay in the polymer matrix. Polymer/clay nanocomposites barrier membranes were generated via different synthesis methods. In the first study, barrier membranes were composed of a polyurethane, Estane ® 58315, and different nanoclays, Cloisite ® 10A, Cloisite ® 20A, Cloisite ® 30B. The interaction of the polyurethane and the different surfactants used to organically modify the nanoclay was evaluated. The dispersion of the clay platelets was analyzed by varying the pre-processing method; sonication vs stirring. The decrease in gas permeability results was enhanced by the effect of pre-processing via sonciation in comparison to plain stirring. These results also suggest that nanoclay platelets modified with alkylammonium groups with one tallow tail Cloisite ® 10A and Cloisite ® 30B, allow better dispersion and penetration of the polymer within the basal spacing of the nanoclays. Once the decrease in gas permeability was confirmed, the next challenge was to study and evaluate the performance of the polyurethane/clay nanocomposites barrier membranes in the determination of diffusivity coefficients for volatile organic compounds (VOCs). This was achieved via gravimetric sorption characterization. This method allowed for characterization of the sorption and desorption phenomena of VOC in barrier membranes. Barrier membranes pretreated with sonication demonstrated lower diffusivity coefficients than those only treated with stirring. At high clay loadings, 50 wt% of nanoclay in the polymer, the decrease in diffusivity coefficients for VOCs such as butanol and toluene, was found to be one order of magnitude. Other VOCs such as decane and tetradecane also showed a significant decrease in diffusivity coefficient. The results for VOC sorption studies suggest that there is some variability. In order to enhance the exfoliation of the clay, we decided to examine in situ polymerization of poly (n-butyl methacrylate) in the presence of nanoclay. In this study the clay wt% was kept at a low concentration of 1-5 wt%. The surface modification of natural montmorillonite, Cloisite ® Na+, was achieved via ion exchange, and the effect of pre-processing was also explored. The modification rendered a tethered group on the surface of the clay that was able to react with the monomer/oligomer chains and thus expand and exfoliate the clay platelets. Gas permeation data suggest that sonication also produced better barrier properties than its counterpart stirring. XRD diffractograms also confirmed exfoliation of the clay platelets in the poly (n-butyl methacrylate) polymer matrix. Thermogravimetric analysis (TGA) suggested that exfoliation of the clay platelets led to improved thermal stability by increasing the decomposition temperature of the membranes. A small increase in Tg also suggested restricted segmental chain motion within the clay platelets. Overall gas permeation decreased even at low clay content. Phenomenological models such as those of Cussler and Nielsen were used to model the experimental permeation results. These models suggest that although the aspect ratio of the clay platelets is within the specifications provided by the manufacturer, it does not reflect the ideal behavior of the models. The last step of this work was to achieve exfoliation of the modified nanoclay platelets via emulsion polymerization of poly (n-butyl methacrylate). The clay concentration in the emulsion was kept the same as in the in situ polymerization. DLS results suggest a uniform distribution of the polymer/clay nanocomposites particles in the emulsion. Permeation data indicated higher permeation values than the in situ method of synthesis of the nanocomposite membranes. This led us to explore the use of glassy co-polymer of poly(n-butyl methacrylate)-poly(methyl methacrylate) as the matrix. The addition of a more glassy component in the polymer matrix led to improved barrier properties of the nanocomposite membranes. As expected, the copolymer had a higher Tg than the PMMA polymer. Analysis via phenomenological models, also suggested that the chemistry of the co-polymer played an important role in decreasing gas permeability within the polymer/clay nanocomposite membranes, although the effect of the glassy component in the matrix was not quantified by the phenomenological models. / Ph. D.

Electron tomography is an invaluable technique with the capability of carrying out thorough 3D structural, chemical and morphological characterization of materials at nanometer scale. Tilting range, increment and reconstruction algorithms are three of the main factors affecting the quality of tomograms. An anisotropic degradation can be observed with restricted tilting range and increment. Therefore, this study was carried out to investigate the accuracy of the reconstruction results of MgO (cube-shape) generated by FBP, SART and SIRT tomographic algorithms under various reconstruction conditions, i.e. tilting range and increment. Examining the experimental data with known morphology permits quantitative determination of the accuracy of the reconstruction results by measuring the distortion of the cube in all directions. Moreover, distortion measurements in all directions reveal the relationship between level of distortion and the alpha tilt angle. / Master of Science

It has been observed that carbon nanotube (CNT)-polymer nanocomposite material has observable piezoresistive effect, that is to say that changes in applied strain may induce measurable changes in resistance. The first focus of the work is on modeling the piezoresistive response of the CNT-polymer nanocomposites by using computational micromechanics techniques based on finite element analysis. The in-plane, axial, the three dimensional piezoresistive responses of the CNT-polymer nanocomposites are studied by using 2D, axisymmetric, and 3D electromechanically coupled and multiscale finite element models. The microscale mechanisms that may have a substantial influence on the overall piezoresistivity of the nanocomposites, i.e. the electrical tunneling effect and the inherent piezoresistivity of the CNT, are included in microscale RVEs in order to understand their influence on macroscale piezoresistive response in terms of both the normalized change in effective resistivity and the corresponding effective gauge factor under applied strain. The computational results are used to better understand the driving mechanisms for the observed piezoresistive response of the material. The second focus of the work is on modeling the piezoresistive response of fuzzy fiber reinforced polymer composites by applying a 3D multiscale micromechanics model based on finite element analysis. Through explicitly accounting for the local piezoresistive response of the anisotropic interphase region, the piezoresistive responses of the overall fuzzy fiber reinforced polymer composites are obtained. The modeling results not only provide a possible explanation for the small gauge factors as observed in experiments, but also give guidance for the manufacture of fuzzy fiber reinforced polymer composites in order to achieve large, consistent, and predictable gauge factors. The third focus of the work is on modeling the coupled effect between continuum damage and piezoresistivity in the CNT-polymer nanocomposites by using computational micromechanics techniques based on a concurrent multiscale finite element analysis. The results show that there is a good correlation between continuum damage and piezoresistive response of the nanocomposites, which gives theoretical and modeling support for the use of CNT-polymer nanocomposites in structural health monitoring (SHM) applications for damage detections. / Ph. D.

Mémoire ou thèse en cotutelle / Les maladies du cœur et des vaisseaux sanguins sont encore aujourd'hui, les principales causes de décès dans la plupart des pays européens, au Canada et aux États-Unis. Souvent, un blocage des artères induit par une sténose entraîne la nécessité d'une chirurgie de pontage. Même si l'utilisation des veines du patient lui-même évite la réponse immunitaire et semble être la solution la plus avantageuse, elle s'avère en fait infructueuse dans un tiers des cas. Pour cette raison, des greffes vasculaires en polytétrafluoroéthylène (PTFE) sont utilisées. Elles présentent de bonnes propriétés mécaniques et une bonne stabilité mais peuvent, dans certains cas, avoir des effets secondaires indésirables et provoquer une hyperplasie néo-intimale à l'interface entre le vaisseau natif et la greffe vasculaire, ce qui en retour peut entraîner une resténose. Afin d'inhiber ce phénomène, il a été proposé d'utiliser un médicament, le mésylate d'imatinib (IM), qui est un inhibiteur de trois récepteurs de kinase à savoir le PDGF-R, le c-Kit et l'abl, les deux premiers étant impliqués dans le mécanisme du phénomène à inhiber. Il a été démontré in vitro que de petites doses de IM inhibent avec succès la prolifération des cellules musculaires lisses (CML) sans ralentir l'endothélialisation. Ce médicament a donc été choisi pour améliorer la fonctionnalité des greffes vasculaires en PTFE. L'objectif de ce projet est de trouver un moyen de développer une approche innovante pour incorporer le mésylate d'imatinib dans les greffons vasculaires et permettre sa libération contrôlée au contact du sang. Pour ce faire, la création de films minces par dépôt chimique en phase vapeur assisté par plasma à pression atmosphérique (AP-PECVD) dans une configuration de décharge de barrière diélectrique (DBD) a été réalisée. Pour protéger le médicament des espèces énergétiques et réactives du plasma, il a été encapsulé dans des nanoparticules (NP) qui ajoutent aussi un autre niveau de contrôle de la libération du médicament. Ainsi, le dépôt d'une couche mince organique nanostructurée par des NPs de silice remplie de médicament a été réalisé sous pression atmosphérique dans un plasma d'argon. Le problème a tout d'abord été abordé par l'étude de la décomposition du précurseur organique dans une DBD plan-plan par spectroscopie infrarouge à transformée de Fourier (IRTF) et la corrélation avec la chimie du film déposé. Dans un premier temps, l'observation d'artéfacts dans les spectres infrarouges du plasma, attribués à tort dans la littérature à des raies de vibration, a été expliquée et décrite mathématiquement. Les résultats obtenus montrent que le nombre d'onde auquel ces artéfacts sont observés dépendent de la fréquence à laquelle est généré le plasma et de la fréquence d'échantillonnage de l'interférogramme mesuré par le spectromètre. En second lieu, la technologie plasma à la pression atmosphérique en mode FSK (Frequency Shift Keying) à 1 kHz et 15 kHz a été mise à profit pour déposer conjointement un polymère plasma, en utilisant le lactate d'éthyle comme précurseur, et des nanoparticules de silices, préalablement dispersées dans le précurseur. Encore une fois, la phase plasma a été caractérisée par spectroscopie infrarouge alors que le nanocomposite obtenu a été étudié par spectroscopie infrarouge, microscopie à balayage et microscopie à force atomique. Ces travaux démontrent clairement que les nanoparticules sont préférentiellement déposées pendant le cycle de basse fréquence de la décharge alors que la polymérisation du précurseur, qui requiert plus d'énergie, est plutôt observée à plus haute fréquence. Par la suite, la spectroscopie infrarouge résolue dans l'espace a été utilisée pour comparer les mécanismes de polymérisation du lactate d'éthyle pour deux modes de décharge, à savoir le régime filamentaire et le régime homogène. Les résultats ainsi générés ont permis de suivre la dégradation du précurseur organique au long de la décharge et de corréler cette information avec la composition du polymère plasma déposé. Ils ont aussi montré que la spectroscopie IRTF du gaz permet de caractériser les NPs. Finalement, les annexes de cette thèse présentent des résultats préliminaires qui visent à démontrer la faisabilité d'application des couches développées à des prothèses vasculaires et le potentiel de la stratégie globale pour inhiber la prolifération des cellules musculaires lisses. En annexe de la thèse, une recherche sur la faisabilité de la création de nanoparticules métalliques dans des plasmas gazeux est abordée et présentée. / Diseases of the heart and blood vessels are still the leading causes of death in most European countries, as well as Canada and the USA. Often, a blockage of the arteries induced by stenosis results in the need for a bypass surgery. Even though, harvesting the vein from the patient himself, avoiding immune response, seems like the most advantageous solution, it does in fact, in one third of the cases, show to be unsuccessful. For that reason, polytetrafluoroethylene (PTFE) vascular grafts are used. They show to have good mechanical properties and stability but could, in some cases, have unwanted side effect and cause neointimal hyperplasia on the interface between the native vessel and the vascular graft, this in return can result in restenosis. In order to inhibit this phenomenon, it has been proposed to use a drug, matinib mesylate (IM), which is an inhibitor of three kinase receptors: PDGF-R, c-Kit and abl, where the first two ones are implicated in the occurrence of neointimal hyperplasia. It has been shown that small doses of IM successfully inhibit SMC proliferation without slowing down the endothelialisation, hence it has been chosen as the drug to improve the functionality of PTFE vascular grafts. The goal of this project was to find a way to develop an innovative approach to incorporate imatinib mesylate into the vascular grafts and enable its controlled release upon contact with the blood. To do that, the creation of thin films by Atmospheric Pressure Plasma Enhanced Chemical Vapor Deposition (AP-PECVD) in a Dielectric Barrier Discharge (DBD) configuration was chosen to be conducted. However, to protect the drug from the energetic and reactive plasma species, nanoparticles (NPs) were used to encapsulate the drug and to act as another level for controlled drug release. Indeed, deposition of an organic nanostructured, by silica nanoparticles, drug-filled thin layer has been achieved under atmospheric pressure in an argon plasma. The way this problem was tackled, was to first study the behavior of the organic precursor in the plasma by in-situ Fourier Transform Infrared Spectroscopy (FTIR), while the thin film is deposited and compare with the characterization of the final layer.First, the observation of artefacts in infrared spectra of plasmas, mistakenly attributed in the literature to vibration lines, was explained and described mathematically. The results obtained show that the wavenumber at which these artefacts are observed depends on the frequency at which the plasma is generated and on the sampling frequency of the interferogram measured by the spectrometer. Secondly, plasma technology at atmospheric pressure in FSK (Frequency Shift Keying) mode at 1 kHz and 15 kHz was used to simultaneously deposit a plasma polymer, using ethyl lactate as a precursor, and silica nanoparticles, dispersed beforehand in the precursor. Again, the plasma phase was characterized by infrared spectroscopy while the resulting nanocomposite was studied by infrared spectroscopy, scanning microscopy and atomic force microscopy. This work clearly shows that the nanoparticles are preferentially deposited during the low frequency cycle of the discharge, while the polymerization of the precursor, which requires more energy, is rather observed at a higher frequency. Subsequently, space-resolved infrared spectroscopy was used to compare the polymerization mechanisms of ethyl lactate for two modes of discharge, namely the filamentary regime and the homogeneous regime. The results thus generated made it possible to follow the degradation of the organic precursor throughout the discharge and to correlate this information with the composition of the plasma polymer deposited. They also showed that FTIR gas spectroscopy makes it possible to characterize the NPs. Finally, the conclusions of this thesis present preliminary results which aim to demonstrate the feasibility of applying the developed layers to vascular prostheses and the potential of the overall strategy to inhibit the proliferation of smooth muscle cells. En annexe de la thèse, une recherche sur la faisabilité de la création de nanoparticules métalliques dans des plasmas gazeux est abordée et présentée.

Molecular weights of 2,000, 6,000 and 10,000 of silane functionalized atactic polystyrene (aPS) and α,ω-divinyl functionalized polydimethylsiloxane (PDMS) were prepared via living anionic polymerization and bulk anionic ring opening polymerization respectively. Functionalization of the homopolymers was confirmed by FT-IR and 1H-NMR spectroscopy and their molecular weights were determined via 1H-NMR end group analysis. A hydrosilylation reaction between the functionalized homopolymers of different molecular weights produced nine polystyrene-block-polydimethylsiloxane-block-polystyrene (aPS-b-PDMS-b-aPS) triblock copolymers. Field emission scanning electron microscopy observations revealed the copolymers self-assemble into supramolecular structures. Dynamic Light Scattering measurements show only small increase in the order of nanometers of its hydrodynamic radius as the individual molecular weights of the homopolymers were increased. Nanocomposites of the copolymers were prepared by incorporating 1% of oxidized single walled carbon nanotubes (SWNTs) within the aPS-PDMS-aPS matrices via coagulation precipitation. Differential scanning calorimetry (DSC) thermal analysis shows the SWNT interacting with both aPS and PDMS constituting blocks. SWNTs interaction with aPS block either increases the polymer glass transition temperature (Tg) by restricting its segmental motion or decreases the Tg by a plasticization effect. Within the PDMS block the SWNTs act as nucleating sites accelerating the crystallization rate of the polymer. This is evident by the appearance of single and double melting endotherms in the DSC thermograms.