In recent years, increased use of electronic devices and wireless operations resulted in unavoidable electromagnetic (EM) pollution which has a significant impact on civil and military sectors. Considering the foremost requirement, huge efforts were invested in the development of electromagnetic interference (EMI) shielding materials. In this context, metals are usually preferred but design complexities like high density and susceptibility towards corrosion are limiting factors; additionally, the reflection of microwaves from the surface fails to serve as EM absorbers. The concern here is to minimize the reflection of the high frequency electromagnetic wave from the surface and to enhance the microwave absorption in GHz frequencies. In this thesis, we have made an attempt to design EMI shielding materials with exceptional absorption ability derived from Polycarbonate (PC)/ Poly styrene-co-acrylonitrile (SAN) based polymer blends. Herein, unique co-continuous micro-phase separated blend structures with selective localization of microwave active nanoparticles in one of the phases were realized to be most effective for microwave attenuation over just dispersing it in one polymer matrix (i.e. PC and SAN composites). The synergistic attenuation of electric and magnetic field associated with EM radiation was achieved through incorporation of various magnetic nanoparticles, however, dispersion of magnetic nanoparticles was a challenging task. Therefore, in order to localize magnetic nanoparticles in PC phase of the blends and to enhance the dispersion state, various modification strategies have been designed. In summary, we have developed a library of engineered nanoparticles to achieve synergistic attenuation of EM radiation mostly through absorption. For instance, the PC/SAN blends containing MWNTs and rGO-Fe3O4 nanoparticles manifested in exceptional EMI shielding, well above required shielding effectiveness value for most of the commercial applications, essentially through absorption. Taken together, the finding suggests that immiscible blends containing MWNTs and the decoration of magnetic nanoparticles (rGO-Fe3O4) on the surface of reduced graphene oxide sheets can be utilized to engineer high-performance EMI shielding materials with exceptional absorption ability.

Ziel der vorliegenden Arbeit war es, die Zusammenhänge zwischen der molekularen Architektur, Morphologie und den mechanischen bzw. bruchmechanischen Eigenschaften in S-SB-S-Triblockcopolymeren und deren Blends und in PI-PS-Multipfropfcopolymeren herauszuarbeiten und damit einerseits einen Beitrag für das Verständnis der Struktur-Eigenschaftsbeziehungen in Block- und Pfropfcopolymeren zu leisten und andererseits Möglichkeiten zur Entwicklung neuer Materialien aufzuzeigen, welche besondere Eigenschaftskombinationen aufweisen und damit ein bedeutendes Interesse für industrielle Anwendungen hervorrufen. Für die Untersuchungen wurde dabei der PS-Außenblockanteil und das S/B-Verhältnis im SB-Mittelblock in S-SB-S-Triblockcopolymeren, die Thermoplast/Thermoplastisches Elastomer (TP/TPE) -Zusammensetzung in S-SB-S-Triblockcopolymer-Blends sowie die Funktionalität und die Anzahl der Verknüpfungspunkte in PI-PS-Multipfropfcopolymeren variiert. Zur Charakterisierung der Phasenmischbarkeit und der Morphologie wurden die dynamisch mechanische Analyse (DMA), die Transmissionselektronenmikroskopie (TEM) und die Röntgenkleinwinkelstreuung (SAXS) angewandt. Die mechanischen Eigenschaften wurden mit dem einachsigen Zugversuch untersucht. Bruchmechanische Untersuchungen erfolgten unter Anwendung der „Essential Work of Fracture“- (EWF-) Methode, welche als Konzept der „Post-Yield“-Bruchmechanik innerhalb der Fließbruchmechanik für duktile nanostrukturierte polymere Materialien sehr gut anwendbar ist und Aussagen zur Bruchzähigkeit der Materialien liefert. Zur näheren Charakterisierung des zeitaufgelösten Deformationsverhaltens sowie der Rissausbreitungskinetik wurden die Dehnungsfeldanalyse, eine Bruchflächenanalyse mittels Rasterelektronenmikroskopie (REM) sowie das Risswiderstandskurven-Konzept angewandt. Die Untersuchungen der S-SB-S-Triblockcopolymersysteme und der PI-PS-Multipfropfcopolymere konnten den signifikanten Einfluss der molekularen Architektur, der Blockzusammensetzung und des PS-Gehaltes auf das Phasenverhalten, die Morphologie und die Eigenschaften klar herausstellen. Durch die Variation dieser Parameter kann das Eigenschaftsspektrum von thermoplastisch zu elastomer eingestellt und somit sowohl TPs oder TPEs mit hoher Steifigkeit und Zähigkeit als auch TPEs mit superelastischem Charakter erzeugt werden. Daraus eröffnet sich ein breiter Anwendungsbereich dieser Materialien, welche aufgrund ihrer Transparenz und physiologischen Verträglichkeit auch interessante optische und gesundheitliche Vorteile mitbringen. Es konnte gezeigt werden, dass durch die systematische Variation der Architektur die gezielte Einstellung gewünschter Eigenschaftsprofile möglich ist. Die Arbeit leistet somit einen Beitrag zur Entwicklung anwendungsorientierter Materialkonzepte, welche ingenieurwissenschaftlich interessant sind. / The aim of this thesis was to study the relation between molecular architecture, morphology and (fracture) mechanical properties of S-SB-S triblock copolymers and PI-PS multigraft copolymers. Hence, this work should contribute to the understanding of structure-property-relationship in block and multigraft copolymers and thus offer possibilities for the development of novel materials with special properties interesting for industrial application. Within this study in the case of S-SB-S triblock copolymers the PS outer block content and the S/B ratio of the middle block, in the case of S-SB-S triblock copolymer blends the thermoplast/thermoplastic elastomer (TP/TPE) composition and in case of PI-PS multigraft copolymers the functionality and number of branch points were varied. For the characterisation of morphology and phase miscibility dynamic mechanical analysis (DMA), transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS) were applied. Uniaxial tensile tests were carried out to investigate the mechanical properties. The fracture mechanical behaviour was studied using essential work of fracture (EWF) concept based on the post yield fracture mechanic principles, which is suitable to characterise fracture toughness of ductile nanostructured materials. The time resolved analysis of deformation and fracture behaviour was characterised qualitatively by strain field analysis, scanning electron microscopy (SEM) of the fractured surfaces and quantitatively by evaluation of the crack propagation kinetics and construction of R-curves. This study clearly highlights the significant influence of molecular architecture block composition and PS content on the phase behaviour, morphology and properties of S-SB-S triblock copolymers and PI-PS multigraft copolymers. By varying these parameters the property profile can be adjusted diversifying from thermoplastic to elastomeric and both TP or TPE materials with high stiffness and toughness and TPEs with super-elastic characteristics can be designed. Hence, fundamentally it offers a broad scope of application of these materials, in which physiological compatibility and transparency are added advantages. Thus, conceptually it could be shown, that by systematic variation of the architecture desired property profiles can be adjusted. Therefore the present work contributes to the development of application-oriented material concepts, which are interesting in engineering terms.

There is a paramount need for online university education to effectively contribute in the development of students' ability to construct and create new knowledge. Online learning should thus go beyond the production of knowledge for knowledge's sake, but should result in relevant and meaningful learning on the part of the online learner. In addition, online learning ought to result in the application of knowledge to practice. While gains made by constructivism and observational learning are well documented, research addressing online media blends that best encourage constructivist and observational learning in open and distance and e-learning (ODeL) contexts is limited. In addition, guidelines that can be used by online learning facilitators and policy makers regarding media for constructivist and observational learning were lacking when this research was conducted. The research was deemed significant in contributing to the development of an online learning framework that could be used to guide policy formulation and practice in the area of online course implementation in ODeL institutions. Using an explorative qualitative approach, this study explored online media blends for constructivist and observational learning. The study comprised three phases. The first phase was a meta-ethnography study whose objective was to synthesise previous research theses in order to gain an understanding of lecturers' and students' experiences of online media, constructivism and observational learning. The second phase consisted of a phenomenological study conducted at the University of South Africa, to explore lecturers' experiences of online media in the facilitation of constructivism and observational learning. The final phase of the research was the development of a framework based on constructivism and observational learning to guide online teaching and learning. The findings of this research study revealed that lecturers did not use media blends to a large extent in their interaction with students. The study indicated that some cognitive processes need to be exercised on the part of the facilitators when online learning is offered. It is concluded that during the curriculum planning phase, lecturers should decide on methods and media to arouse the students' attention during online courses. This also implies a more reasonable lecturer­ student ratio because large numbers of students per lecturer is not feasible in online learning. / Curriculum and Instructional Studies / D. Ed. (Curriculum Studies)

La spectroscopie infrarouge à matrice à plan focal (PAIRS) est utilisée pour étudier la déformation et la relaxation des polymères à très haute vitesse, soit de 46 cm/s, grâce à sa résolution temporelle de quelques millisecondes. Des mesures complémentaires de spectroscopie infrarouge d’absorbance structurale par modulation de la polarisation (PM-IRSAS) ont été réalisées pour suivre des déformations plus lentes de 0,16 à 1,6 cm/s avec une résolution temporelle de quelques centaines de millisecondes. Notre étude a permis d’observer, à haute vitesse de déformation, un nouveau temps de relaxation (τ0) de l’ordre d’une dizaine de millisecondes qui n’est pas prédit dans la littérature. Le but de cette étude est de quantifier ce nouveau temps de relaxation ainsi que de déterminer les effets de la température, de la masse molaire et de la composition du mélange sur ce dernier. Des mesures effectuées sur du polystyrène (PS) de deux masses molaires différentes, soit 210 et 900 kg/mol, à diverses températures ont révélé que ce temps est indépendant de la masse molaire mais qu’il varie avec la température. Des mesures effectuées sur des films composés de PS900 et de PS deutéré de 21 kg/mol, ont révélé que ce temps ne dépend pas de la composition du mélange et que la longueur des chaînes de PS n’a aucun impact sur celui-ci. D’autres mesures effectuées sur des films de PS900 mélangé avec le poly(vinyl méthyl éther) (PVME) ont révélé que ce temps est identique pour le PS900 pur et le PS900 dans le mélange, mais qu’il est plus court pour le PVME, de l’ordre de quelques millisecondes. / Planar array infrared spectroscopy (PAIRS) was used to study the fast deformation and relaxation of polymers at s draw rate of 46 cm/s, giving millisecond time resolution. Complementary measurements by polarization modulation infrared structural absorbance spectroscopy (PM-IRSAS) were conducted to probe slower deformations (0.16 to 1.6 cm/s) with a time resolution of a few hundreds of milliseconds. Our study allowed the observation, after fast deformation, of a new relaxation time (τ0), on the order of tens of milliseconds, which was not predicted in the literature. The aim of this work is to quantify this new relaxation time and to determine how it is affected by molecular weight, temperature, and blending. Measurements performed on polystyrene (PS) with two different molecular weights (210 and 900 kg/mol) at various temperatures revealed that the new relaxation time is independent of the molecular weight, but that it varies with temperature. Measurements performed on film blends of PS900 with deuterated PS of low molecular weight (21 kg/mol) indicated that this time is unaffected by blending and that the PS chain length has no impact on it. Measurements on films of PS blended with poly(vinyl methyl ether) (PVME) revealed that it is identical for pure PS and for PS in the blends, but that it is shorter, on the order of few milliseconds, for PVME.

<p>Ova disertacija se bavi procesom<br />&nbsp;morfemizacije krnjih osnova koje su nastale<br />od leksičkihslivenica. Rekurzivinim<br />slivanjem s različitim inicijalnim elementima,<br />ove osnove se konsoliduju u svom skraćenom<br />obliku ili oblicima, &scaron;to za rezultat ima<br />separaciju novih tvorbenih jedinica. Najbitniji<br />ciljevi istraživanja su sledeći: da se utvrdi<br />teorijski i terminolo&scaron;ki status ovih elementa i<br />odrede kriterijumi za njihovo članstvo u ovoj<br />kategoriji; da se na osnovu tih kriterijuma<br />napravi popis morfemizovanih elemenata uz<br />razvoj metodologije potrebne za njihovu<br />ekscerpciju; da se sačini spisak leksema u<br />kojima se javljaju; da se ustanove formalne<br />varijacije i njihova relativna učestalost kao i<br />tipovi i oblici inicijalnih elementa sa kojima<br />se kombinuju, &scaron;to bi za rezultat imalo<br />formulisanje prototipskog tvorbenog modela;<br />da istraži značenje ovih elemenata, eventualni<br />razvoj novih semema i smisaonih odnosa; da<br />d&acirc; pregled njihove zastupljenosti u<br />postojećim rečnicima; da predloži model<br />njihove leksikografske obrada i da se na<br />osnovu tog predloga sačini rečnik kako<br />morfemizovanih krnjih osnova, tako i reči u<br />kojima se javljaju.</p> / <p>This dissertation investigates the process of<br />AB morphemization of truncated bases which<br />have originated from lexical blends. Through<br />their recurrent blending with various initial<br />elements, they become consolidated in their<br />truncated form or forms, resulting in the<br />secretion of new word-formational units. The<br />most important goals of the research are the<br />following: to determine the theoretical and<br />terminological status of these elements and<br />establish the criteria for category<br />membership; to compile a list of<br />morphemized elements based on these<br />criteria by developing the methodology for<br />their extraction; to compile a list of lexemes<br />containing these newly morphemized<br />elements; to determine formal variations and<br />their relative frequency as well as the types<br />and forms of initial elements with which they<br />combine, resulting in theformulation of the<br />prototypical word-formation pattern; to<br />investigate the meaning of these elements and<br />the development of new senses and sense<br />relations; to give an overview of their<br />representation in existing dictionaries; to<br />propose a model for their lexicographic<br />treatment and to apply that model in the<br />compilation of a specialized dictionary of<br />morphemized truncated bases and words in<br />which they appear.</p>

L’électrofilage est un procédé permettant de préparer des fibres possédant un diamètre de l’ordre du micromètre ou de quelques centaines de nanomètres. Son utilisation est toutefois limitée par le manque de contrôle sur la structure et les propriétés des fibres ainsi produites. Dans ce travail, des fibres électrofilées à partir de mélanges de polystyrène (PS) et de poly(vinyl méthyl éther) (PVME) ont été caractérisées. La calorimétrie différentielle à balayage (DSC) a montré que les fibres du mélange PS/PVME sont miscibles (une seule transition vitreuse) lorsque préparées dans le benzène, alors qu'une séparation de phases a lieu lorsque le chloroforme est utilisé. Les fibres immiscibles sont néanmoins malléables, contrairement à un film préparé par évaporation du chloroforme qui a des propriétés mécaniques médiocres. Des clichés en microscopies optique et électronique à balayage (MEB) ont permis d’étudier l'effet de la composition et du solvant sur le diamètre et la morphologie des fibres. Des mesures d’angles de contact ont permis d’évaluer l’hydrophobicité des fibres, qui diminue avec l’ajout de PVME (hydrophile); les valeurs sont de 60° supérieures à celles des films de composition équivalente. Un retrait sélectif du PVME a été réalisé par l’immersion des fibres dans l’eau. La spectroscopie infrarouge a montré que la composition passe de 70 à 95% de PS pour une fibre immiscible mais seulement à 75% pour une fibre miscible. Ces résultats indiquent que la phase riche en PVME se situe presque uniquement à la surface des fibres immiscibles, ce qui a été confirmé par microscopie à force atomique (AFM) et MEB. Finalement, l’effet du mélange des deux solvants, lors de l’électrofilage du mélange PS/PVME, a été étudié. La présence du chloroforme, même en quantité réduite, provoque une séparation de phases similaire à celle observée avec ce solvant pur. / Electrospinning is a simple method for the preparation of polymer fibers with diameters of hundreds of nanometers to a few micrometers. Although it is a versatile method, some issues remain in the control of the structure and properties of electrospun fibers. In this study, fibers electrospun from polystyrene (PS)/poly(vinyl methyl ether) (PVME) blends were characterized. Differential scanning calorimetry (DSC) revealed that fibers electrospun from benzene are miscible while a phase separation occurs when the fibers are electrospun from chloroform. While films cast from chloroform show poor mechanical properties, immiscible fibers are ductile. The effects of the blend composition and the solvent on the fiber diameter and morphology were observed by scanning electron microscopy (SEM) and optical microscopy. Afterwards, contact angle measurements were made to evaluate the hydrophobicity of the fibers which decreases as hydrophilic PVME is added to the blend; the values for the fibers were found to be 60° higher than their equivalent in films. PVME was selectively removed from the immiscible fibers by complete immersion into water. Infrared spectroscopy revealed that this process increases the PS content from 70 to 95% for immiscible fibers but only to 75% for miscible fibers. These results show that the PVME-rich phase is almost completely distributed on the fiber surface, which was confirmed by atomic force microscopy (AFM) and SEM. Finally, the electrospinning of PS/PVME blends from chloroform/benzene solutions was studied. The presence of chloroform, even as a residual amount, causes a phase separation just as it does in fibers electrospun from pure chloroform.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Orientador: Ricardo Alan Verdú Ramos / Resumo: Resumo / Abstract: Abstract / Doutor

Neste trabalho estudou-se o comportamento reológico e morfológico da mistura polimérica imiscível de polipropileno e poliamida. Como resultado deste estudo obtiveram-se valores de tensão interfacial entre 10mN/m e 13mN/m. A tensão interfacial diminuiu em até 87% quando a mistura é compatibilizada com polipropileno maleado. A análise morfológica no regime de viscoelasticidade linear quando avaliada uma morfologia de emulsão de poliamida em polipropileno revelou diâmetro médio da fase dispersa entre 1,5µm e 20µm. O diâmetro das gotas da fase dispersa diminuiu com a adição de polipropileno maleado chegando a reduções de até 98%, mantendo-se constante a concentração da fase dispersa. No regime de viscoelasticidade não linear foram testados modelos para avaliar o comportamento da mistura em fluxos de cisalhamento e extensão, sendo que somente para os fluxos de extensão foi obtida boa correlação dos resultados experimentais com as previsões teóricas. / Rheological and morphological behaviour of polypropylene and polyamide polymer blend was studied. The values of interfacial tension were obtained between 10mN/m and 13mN/m. The interfacial tension decreased in 87% for compatibilized blend. Morphology analysis for linear viscoelastic regime shows dispersed drop diameter between 1,5µm and 20µm. The diameter of the drops decreased with the addition of maleic polypropylene reducing until 98%, keeping constant the concentration of the disperse phase. In non linear viscoelastic regime different models were tested to evaluate the behavior of the blends in shear and elongacional flows. However, only the elongacional flow results were acquired with theoretical - experimental corroboration.

Des masques polymères à porosité contrôlée sont fabriqués à partir de films minces de copolymères à blocs auto-organisés polystyène-b-polylactide (PS-PLA) et polystyrène-b-poly(méthacrylate de méthyle) (PS-PMMA). Les films doivent être réorganisés grâce à une exposition aux vapeurs de solvant (THF ou DCE) pour obtenir des cylindres perpendiculaires à la surface, dans le volume et arrangés de façon hexagonale à longue distance. L’extraction sélective des domaines minoritaires conduit alors à des films minces poreux de PS. La mise en place de nouvelles techniques de caractérisation (analyse des images AFM, analyse MEB de répliques de système poreux, ellipso-porosimétrie) a permis d’évaluer l’influence de nombreux paramètres (nature du substrat, épaisseur du film, mode de dépôt, nature du solvant, temps et mode d’exposition aux vapeurs du solvant, …) sur la morphologie des films (surface, interface substrat/film, volume) et sur la cinétique de réorganisation. Des mélanges de copolymères à blocs A-B et d’homopolymères C (PS-PMMA/PLA, PS-PLA/PMMA, PS-PLA/PEO, PS-PEO/PLA, PS-PEO/PMMA, PS-PMMA/PEO) sont également étudiés. L’ajout d’homopolymères permet dans certains cas, d’améliorer la réorganisation des films de copolymères à blocs. Il permet également une augmentation des tailles caractéristiques du système. L’homopolymère C se localise au centre des domaines du bloc minoritaire B si χA-C> χB-C et χA-C > χA-B. Par exemple, dans le cas du mélange PS-PMMA/PLA, des cylindres perpendiculaires à la surface et organisés de façon hexagonale sont observés après exposition aux vapeurs de THF avec incorporation des domaines d’homopolymères PLA au centre des domaines de PMMA. / Polymer films with controlled porosity are obtained from block copolymer thin films of polystyrene-b-polylactide (PS-PLA) and polystyrene-b-poly(methylmethacrylate) (PS-PMMA). The morphology of these films must be reorganized by solvent annealing (THF or DCE) in order to obtain the cylinders perpendicular to the surface, in the volume and arranged in a hexagonal lattice over a long distance. The selective removal of the minority domains leads to a porous thin film of PS. New characterization techniques (AFM image analysis, SEM analysis of the silica replica, ellipsoporosimetry) are developed to evaluate the influence of various parameters (substrate nature, film thickness, method of deposition, duration and method of solvent vapors annealing …) on the morphology of the film (surface, interface and volume) and on the kinetics of reorganization. Blends of copolymer/homopolymer A-B/C (PS-PMMA/PLA, PS-PLA/PMMA, PS-PLA/PEO, PS-PEO/PLA, PS-PEO/PMMA, PS-PMMA/PEO) are also studied. In some cases, the addition of homopolymers can improve the reorganization of block copolymer films. It also allows an increase of the characteristics size of the system. Homopolymers C locate at the center of the minority B domains if χA-C> χB-C and χA-C> χA-B. For example, in the case of PS-PMMA/PLA blends, cylinders perpendicular to the surface and hexagonally arranged are observed after exposure to vapor of THF with incorporation of PLA homopolymer in central PMMA domains.