La thèse détermine les principaux paramètres de la formation des structures de la phase conductrice de nanocomposites polymères chargés avec des nanotubes de carbone (NTC) ou des nanocharges combinées, pour étudier l'influence de la morphologie de la structure hétérogène du composite et l'interaction des nanocharges sur les propriétés électriques, thermophysiques et mécaniques des composites. Les trois types de systèmes polymères ont été étudiés, à savoir: 1) les systèmes ségrégés avec distribution ordonnée de nanocharges, 2) les mélanges polymère conducteur; 3) les composites avec des charges binaires où les nanotubes de carbone ont été combinés avec des composés organo-argileux modifiés (MOC) dans un cas et des nanoparticules métalliques d’autre part. Les résultats sur les composites polymères ségrégés chargés avec des NTC ont montré que dans de tels systèmes, la charge conductrice crée un réseau continu conducteur au sein de la matrice polymère. Cela conduit à un seuil de percolation ultra faible avec la valeur de φc~0,045vol.%. Il a été démontré que les systèmes conducteurs à base de mélanges de polymères ont un seuil de percolation inférieur en raison d'effet de double percolation. Il a été constaté que l'introduction simultanée de composés MOC et de NTC dans la matrice thermoplastique permet une meilleure répartition des nanotubes de carbone, ce qui empêche leur agrégation. Il en résulte une diminution du seuil de percolation des composites. Il a été démontré que la formation de la phase conductrice est plus efficace avec des charges mixtes CNT/nanométal en comparaison avec les charges individuelles / The thesis research field determines the main parameters, of the conductive phase structure formation in polymer nanocomposites filled with conductive fillers such as carbon nanotubes (CNTs) or combined nanofillers. The influence of the morphology of the heterogeneous structure of the composite and interaction of nanofillers on the electrical, thermophysical and mechanical properties of the composites was studied. The three types of polymer systems filled with carbon nanotubes have been investigated, namely: 1) segregated systems with ordered distribution of the nanofiller; 2) conductive polymer blends; 3) composites with binary fillers in which carbon nanotubes have been combined with organo-modified clay (OMC) in one case and with metal nanoparticles in another case. The investigation of the segregated polymer composites filled with CNTs has shown that the conducting filler creates continuous conductive framework inside the polymer matrix. This provides the presence of ultralow percolation threshold with the value of φc~0.045vol.%. Conductive polymer blends have demonstrated a lower percolation threshold in comparison with individually filled polymers due to a double percolation effect. It has been found that the simultaneous introduction of OMC and CNTs into thermoplastic matrix provides a better distribution of carbon nanotubes, preventing their aggregation and decreasing the percolation threshold. It has been shown that the formation of the conducting phase is more effective in the polymeric matrix with combined nanofillers CNT/nanometal in comparison with individual fillers and the higher conductivity of such conductive system is due to metallic filler content

Cette étude décrit l’élaboration de nouveaux multifilaments textiles offrant un compromis ténacité/élasticité inédit. Ces multifilaments sont composés de mélanges de polymères immiscibles, soit PA66/élastomère soit PET/élastomère, compatibilisés tous les deux par des liquides ioniques. L’incorporation de 1%m de liquide ionique dans ces mélanges a permis de diminuer la tension interfaciale entre les polymères, permettant ainsi d’affiner les morphologies des mélanges binaires et d’améliorer les propriétés mécaniques. Cette compatibilisation a été réalisée sans augmentation de la viscosité des mélanges, critère indispensable pour conserver la filabilité des formulations. L’utilisation de liquide ionique a également permis de façonner la morphologie des mélanges en choisissant judicieusement le couple « cation/anion ». La nature du cation (phosphonium vs imidazolium) et de l’anion a été étudiée. Ainsi, des morphologies nodulaires, fibrillaires ou intermédiaires ont pu être obtenues avec des propriétés mécaniques différentes. De nombreuses formulations ont pu être filées, étirées, puis prototypées sous forme de tissus et cordages de tennis afin de tester l’apport élastique des élastomères. Les liquides ioniques capables de réagir chimiquement avec le thermoplastique ouvrent des perspectives intéressantes. / This work highlights the role of ionic liquids (ILs) as compatibilizers in immiscible polymer blends to increase the springback of polyamide or polyester multiyarns due to the presence of elastomeric nodules. The influence of ionic liquid nature on the morphology of PA66/rubber and PET/rubber blends and on thermal, rheological and mechanical properties has been investigated. The incorporation of only 1 wt% of ionic liquids leads to a decrease of interfacial tension between the polymers. The morphology of blends can be tuned by the chemical nature of ionic liquids to reduce largely the nodule size of the dispersed phase and/or to generate fibrillar shape morphology. The reduction of particles size leads to an improvement of mechanical properties with an increase of elongation at break and the same stiffness. Moreover the incorporation of IL has no effect on the viscosity of blends. Several formulations could be spun and prototypes of fabric and tennis racket strings could be made with multiyarns.

博士(工学) / Doctor of Philosophy in Engineering / 同志社大学 / Doshisha University

Semiconductors are used in many electronic applications, for example diodes, solar cells and transistors. Typically, semiconductors are inorganic materials, such as silicon and gallium arsenide, but lately more research and development has been devoted to organic semiconductors, for example semiconducting polymers. One of the reasons is that polymers can be customized, to a greater extent than inorganic semiconductors, to create a material with desired properties. Often, two polymers are blended to obtain the desired function, but two polymers do not usually result in an even blend. Instead they tend to separate from each other to varying degrees. The morphology of the blend affects the material properties, for example how efficiently it can convert electricity to light. In this project, thin films consisting of polymer blends were examined using microscopy techniques for the purpose of increasing our understanding of the morphology of such blends. One goal was to investigate whether a technique called correlative light and electron microscopy can be useful for examining the morphology of these films. In correlative light and electron microscopy, a light microscope and an electron microscope are used in the same location in order to be able to correlate the information from the two microscopes. The second goal was to learn about the morphology of the thin films using various microscopy techniques. The polymers used were Super Yellow and poly(ethylene oxide) with large molecular weight. Super Yellow is a semiconducting and light-emitting polymer while poly(ethylene oxide) is an isolating and non-emitting polymer that can crystallize. In the blend films, large, seemingly crystalline structures appeared. The structures could be up to 1 mm in the lateral direction, while the films were only approximately 170 nm thick. These structures could grow after the films had dried and their shapes were similar to those of poly(ethylene oxide) crystals. Consequently, there is reason to believe that it is the poly(ethylene oxide) that makes up the seemingly crystalline structures, but the structures also emitted more light than the rest of the film, and Raman spectroscopy showed that there was Super Yellow in the same location as the crystals. Among the microscopy techniques used, phase contrast microscopy was particularly interesting. This method visualizes differences in optical path length and was useful for studying polymer blends when the polymers have different indices of refraction. Correlating light and electron microscopy showed that there was a pronounced topographical difference between the seemingly crystalline regions and the rest of the thin film. Light microscopy has a limited resolution due to diffraction, but as long as the resolution of the light microscope is sufficient for seeing phase separation, correlative light and electron microscopy turned out to be a good method for studying the morphology of thin films of polymer blends. / Halvledare är viktiga för många elektroniska ändamål eftersom de kan användas till exempelvis dioder, solceller och transistorer. Traditionellt används inorganiska halvledande material som kisel eller galliumarsenid, men på senare tid har allt mer forskning och utveckling inriktat sig mot organiska (kolbaserade) halvledare, såsom halvledande polymerer, bland annat eftersom det i högre utsträckning går att skräddarsy de organiska materialen så att de får önskvärda egenskaper. Ofta blandas två polymerer med varandra för att skapa ett material med nya egenskaper som är önskvärda, men två polymerer brukar inte blandas jämnt utan tenderar att separera från varandra i olika utsträckning. Hur blandningen ser ut (morfologin) påverkar materialets egenskaper, till exempel hur effektivt det omvandlar ström till ljus. Med syfte att öka förståelsen för hur morfologin ser ut hos en blandning av två polymerer, har detta projekt gått ut på att undersöka tunna filmer av polymer-blandningar med hjälp av mikroskopiska tekniker. Ett delmål var att ta reda på om en teknik som heter korrelativ ljus- och elektronmikroskopi är en bra metod för att undersöka morfologin hos dessa filmer. Vid korrelativ ljus- och elektronmikroskopi används både ett ljusmikroskop och ett elektronmikroskop på samma plats för att kunna korrelera informationen som de båda mikroskopen ger. Det andra delmålet var att undersöka vad de olika mikroskopi-teknikerna kan säga om morfologin hos de tunna filmerna. De polymerer som använts är Super Yellow och poly(etylenoxid) med hög molekylmassa. Super Yellow är en oordnad halvledande och ljusemitterande polymer medan poly(etylenoxid) är en isolerande och icke-emitterande polymer som kan kristallisera. I de blandade filmerna uppstod stora kristall-liknande strukturer som kunde vara upp emot 1 mm breda trots att filmerna bara var ungefär 170 nm tunna. Dessa strukturer kunde växa fram efter det att filmerna redan hade torkat och påminde i form om kristaller som kan bildas av poly(etylenoxid). Det finns alltså skäl att tro att det är poly(etylenoxid) som kristalliserats, men de kristall-liknande strukturerna visade sig emittera mer ljus än vad resten av filmen gjorde, och Raman-spektroskopi visade att det även fanns Super Yellow på samma plats som kristallerna. Bland de mikroskopitekniker som testades utmärker sig faskontrastmikroskopi, som visar skillnader i den optiska vägskillnaden (det vill säga faktisk vägskillnad multiplicerat med brytningsindex). Det visade sig vara en intressant teknik för att studera polymerblandningar när de båda polymererna har olika brytningsindex. Genom att korrelera ljus- och elektronmikroskopi visade det sig att det fanns en tydlig skillnad i struktur mellan de kristall-liknande områdena och resten av den tunna filmen. Ljusmikroskopi har begränsad upplösning på grund av ett fenomen som heter diffraktion, men så länge som ljusmikroskopets upplösning är tillräcklig för att se fasseparation visade det sig att korrelativ ljus- och elektronmikroskopi är en bra metod för att studera morfologin hos tunna filmer av polymerblandningar.

Magister Scientiae - MSc (Chemistry) / Blending polymers together offers researchers the ability to create novel materials that have a combination of desired properties of the individual polymers for a variety of functions as well as improving specific properties. The behaviour of the resulting blended polymer or blend is determined by the interactions between the two polymers. The resultant synergy from blending an intrinsically conducting polymer like polyaniline (PANI), is that it possesses the electrical, electronic, magnetic and optical properties of a metal while retaining the poor mechanical properties, solubility and processibility commonly associated with a conventional polymer. Aromatic polyamic acid has outstanding thermal, mechanical, electrical, and solvent resistance properties that can overcome the poor mechanical properties and instability of the conventional conducting polymers, such as polyaniline.