Dissertations / Theses on the topic 'Methacrylic copolymer'

Polymers in concrete have received considerable attention over the past 30 years. Superplasticizers are one of the admixtures which have polymeric structure. In this study, polycarboxylate type slump-releasing dispersant, which is a copolymer of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and methacrylic acid (MAA), was synthesized in different feed compositions. The synthesis procedure of this copolymer was retrieved from literature. The derivatives of this water-soluble copolymer (AMPS-MAA) were synthesized by a macromonomer which was synthesized by the esterification of poly(ethylene glycol) methyl ether (PEG) with MAA (PEGMA) and then copolymerizing this macromonomer with AMPS monomer, the resulting copolymer is AMPS-PEGMA. In order to study the methyl group effect on fluidity, the other type of macromonomer (PEGA), composed of PEG and acrylic acid (AA), was synthesized and copolymerized with AMPS monomer, giving AMPS-PEGA. The structures of synthesized polymers were verified by NMR and FT-IR analysis. The slump-releasing effect of the synthesized copolymers was studied in terms of reaction pH, composition, molecular weight, amount of PEG side chains, and molecular weight of PEG side chains. The AMPS-MAA copolymer with 40% AMPS content was the most effective in promoting the fluidity of cement pastes. In scope of reaction pH, the AMPS-MAA copolymer, synthesized at a pH of 11, gave the most effective result on fluidity of the cement pastes. In copolymers of PEG acrylate macromonomers and AMPS monomers, copolymers with 5% PEG acrylate content showed the highest fluidity both in copolymers of PEGA and PEGMA. In copolymers with PEG side chains, the 15% AMPS-PEGA copolymer synthesized at pH of 6 gave the most effective result on fluidity of cement pastes. In the study of mechanical properties of the mortar samples prepared by the copolymers selected, AMPS-PEGA copolymer with 25% PEG content showed the highest flexural strength, and AMPS-MAA copolymer with 60% AMPS content and a reaction pH of 11 gave the highest compressive strength. In this study, zeta potential measurements were also performed to analyze the fluidity behavior of the copolymers.

The wetting behavior of water on methacrylate copolymer films was studied on anodically oxidized and micro-roughened aluminium surfaces and also on smooth model surfaces. The copolymerization of tert-butyl methacrylate with a methacrylate containing a fluoroorganic side chain led to a considerable decrease of the surface free energy, but not to a superhydrophobic behavior of polymer-coated, micro-roughened aluminium surfaces. However, copolymers containing both hydrophobic and hydrophilic sequences are able to form superhydrophobic films. X-ray photoelectron spectroscopy showed that an enrichment of the interface between the solid phase and the air by fluorine-containing polymer components was the reason for the strong decrease of the surface free energy. The hydrophilic segments of the copolymers improved the ability to wet the highly polar aluminium surface and to form films of higher density.

The wetting behavior of water on methacrylate copolymer films was studied on anodically oxidized and micro-roughened aluminium surfaces and also on smooth model surfaces. The copolymerization of tert-butyl methacrylate with a methacrylate containing a fluoroorganic side chain led to a considerable decrease of the surface free energy, but not to a superhydrophobic behavior of polymer-coated, micro-roughened aluminium surfaces. However, copolymers containing both hydrophobic and hydrophilic sequences are able to form superhydrophobic films. X-ray photoelectron spectroscopy showed that an enrichment of the interface between the solid phase and the air by fluorine-containing polymer components was the reason for the strong decrease of the surface free energy. The hydrophilic segments of the copolymers improved the ability to wet the highly polar aluminium surface and to form films of higher density.

Une corrélation entre l’intensité et la nature des interactions intermoléculaires et les propriétés physiques, comme la conductivité thermique, a été rapportée pour des polymères amorphes. En particulier, une augmentation de la conductivité thermique a été associée à l’ajout d’interactions plus fortes par rapport aux liaisons de Van der Walls faibles, c’est-à-dire des liaisons hydrogène et ioniques. Dans ce travail, une tentative d'adapter la conductivité thermique dans les polymères amorphes a été réalisée par ingénierie des interactions intermoléculaires. Le poly(méthylméthacrylate) PMMA a été utilisé comme modèle et des copolymères poly(méthylméthacrylate-co-acide méthacrylique) (PMMA-co-MAA) ont été synthétisés par copolymérisation radicalaire afin d'introduire des liaisons H inter-chaînes et, après neutralisation, des liaisons ioniques. Des copolymères ont été obtenus avec succès jusqu'à 30 % en poids de MAA et caractérisés. Différents comonomères ont été utilisés pour évaluer l'influence d'une unité flexible apportant des liaisons H, le 2-hydroxyéthylméthacrylate (HEMA) ou le 2-carboxyéthylacrylate (CEA). La conductivité thermique a légèrement augmenté en augmentant la teneur en MAA et HEMA, tandis que pour les copolymères CEA, la présence de défauts a empêché la mesure. Le copolymère PMMA-co-MAA a été utilisé comme matrice pour les nanocomposites à base de cellulose afin d'adapter la compatibilité des charges, grâce à la présence de liaisons H entre l'unité MAA et la surface de la cellulose. Des nanofibres de cellulose (CNF) jusqu'à 15 % en poids ont été efficacement dispersées par coulée de solvant dans un mélange de deux solvants (THF/MeOH). La conduction thermique n'a montré aucun changement significatif après l'introduction des CNF. L'analyse mécanique dynamique (DMA) et la spectroscopie diélectrique à large bande (BDS) ont été utilisées en combinaison pour caractériser pleinement la dynamique moléculaire du PMMA-co-MAA copolymère suite à l'introduction de liaisons H inter-chaînes et à l'ajout ultérieur de CNF. Une relaxation β’ supplémentaire, caractérisée par une énergie d’activation (Ea) presque quatre fois plus élevé que le Ea(β), a été trouvée pour les nanocomposites et attribuée à l’établissement de liaisons H entre les groupes -COOH de la matrice et les groupes hydroxyles du CNF. Ainsi, une étude plus approfondie de la relaxation α a permis de révéler l’influence du CNF confirmant la présence de liaisons H interfaciales. En effet, malgré les Tgs similaires caractérisant la matrice et les nanocomposites, un décalage de leurs temps de relaxation vers des températures plus élevées a été observé suite à l’ajout de CNF. Les résultats rapportés dans cette thèse ont mis en évidence que les améliorations de la conductivité thermique obtenues par la modification des interactions entre les chaînes dans les matrices amorphes restent un défi extrêmement complexe
A correlation between the strength of the intermolecular interactions and physical properties has been reported for amorphous polymers. In particular, an increment of thermal conductivity has been associated to the addition of stronger interactions compared with weak van der Walls, i.e. hydrogen and ionic bonds. In this work, an attempt to tailor thermal conductivity in amorphous polymers has been made by engineering intermolecular interactions. Poly(methylmethacrylate) PMMA was used as standard and poly(methylmethacrylate-co-methacrylic acid) (PMMA-co-MAA) copolymers were synthesised by free radical copolymerization in order to introduce inter-chain hydrogen bonds and, after neutralisation, ionic bonds. Copolymers were successfully obtained up to 30wt% of MAA and characterized. Also, different comonomers were used to evaluate the influence of a flexible unit bringing H-bonds, 2-hydroxyethylmethacrylate (HEMA) or 2-carboxyethylacrylate (CEA). Thermal conductivity slightly increased increasing MAA and HEMA content, while for CEA copolymers the presence of defects prevented the measurement. Later, PMMA-co-MAA was used as a matrix for cellulose-based nanocomposites to tailor filler compatibility, thanks to the presence of H-bonds between MAA unit and cellulose surface. Cellulose nanofibers (CNF) up to 15wt% were efficiently dispersed by solvent casting in a mixture of two solvents (tetrahydrofuran/methanol). Thermal conduction showed no significant changes following the introduction of CNF. Dynamic mechanical analysis (DMA) and broadband dielectric spectroscopy (BDS) were used in combination to fully characterize the macromolecular mobility of PMMA-co-MAA following the introduction of inter-chain H-bonds and the subsequent addition of CNF. An additional β’-relaxation, characterized by an activation energy (Ea) nearly four times higher than the Ea(β), was found for the nanocomposites and ascribed to the establishment of H-bonds between the -COOH groups of the matrix and the hydroxyl groups of CNF, as confirmed by the lower values found for the thermal expansion coefficient of the free volume and the fragility of the material. A deeper investigation about the α-relaxation was able to reveal the influence of CNF confirming the presence of interfacial H-bonds. Indeed, despite the similar glass transition temperatures characterising the matrix and the nanocomposites, a shift of their relaxation times to higher temperatures was observed following the addition of CNF. Results reported in this thesis evidenced that the enhancements of thermal conductivity obtainable by the modification of the interchain interactions between chains in amorphous matrices remains an extremely complex challenge

Fluoropolymers are a versatile and attractive group of compounds having an interesting mix of properties that make them highly useful for various applications. Because of strong bonding between the carbon and fluorine atom, they exhibit unique physical and chemical properties such as high thermal stability, increased chemical resistance, low refractive index, enhanced inertness towards many solvents and hydro-compounds. These characteristics have led them to be widely used in aerospace, aeronautics, optics, microelectronics, paints and coatings, and engineering structures and as biomaterials. Amphiphilic copolymers possess unique solution and solid-state properties due to their well-defined molecular architecture. These properties arise as the result of covalently combining two thermodynamically different polymer blocks that phase separate on the nanoscale. Amphiphilic copolymers based on a fluoro-monomer will combine the favourable physiochemical properties of the desired fluorine segment in combination with complementary hydrophilic segments. Such fluorinated amphiphilic copolymers are potentially useful for drug delivery vehicles and membrane applications. This project is aimed at making fluorinated amphiphilic block copolymers of hydrophobic 2, 3, 4, 5, 6 –pentafluorostyrene (PFS) and hydrophilic methacrylic acid (MAA). A controlled radical polymerization mechanism, nitroxide mediated polymerization (NMP) using NHS-BlocBuilder as the initiator was employed. The advantage of using NMP is that it facilitates the synthesis of copolymers with well-controlled narrow molecular weight distribution. However, methacrylate homopolymerization by NMP is challenging due to the high dissociation equilibrium constant therefore, the use of PFS as a controlling comonomer was explored. We established that to obtain a controlled copolymerization, a minimum of 70 mol% PFS was required, which is significantly greater than other copolymerization systems such as using as little as 4.5-8 mol% styrene to control the copolymerization of MAA. We surmise that this lack of control is due to the unfavourable reactivity ratios (Appendix I) which favour the addition of MAA rather than PFS (rPFS = 0.012, rMAA = 8.12). However, these unique reactivity ratios suggest that a semi-batch approach can be utilized to synthesize almost pure block copolymers in one pot. Therefore, poly(PFS)–b-(PFS-ran-MAA) block copolymers were synthesized and characterized by a semi batch addition of MAA. While successful, the concentration of irreversibly terminated chains was evident and greater care in reducing these unwanted reactions needs to be addressed.

Poly(ethylene-co-methacrylic acid) (EMAA) ionomer polymers carry great potential for use in a wide variety of unique applications due to their property of “self-healing” following projectile impact. Following puncture, certain films based on these materials are observed to “heal”, with the penetration opening recovering to an air-tight condition. Specifically, four polymers of this class were examined, including DuPont™ Surlyn® 8920, Surlyn® 8940, Nucrel® 925, and Nucrel® 960. Though these differ in their amount of ionic content, all expressed a certain degree of self-healing. Thin films were prepared by a compression molding process and punctured at temperatures ranging from room up to that of the melt using a pellet gun. Samples were then assessed for self-healing. A quantitative post-puncture burst-test method examined the strength or quality of the healed site in the four examples. A comparison of this data provided an understanding of the importance of ionic content and the mechanism of puncture healing. Additional damage modes were also examined to determine other cases where healing occurs and the requirements necessary to elicit the healing response. In addition, interesting composite materials consisting of carbon nanotube filled ionomers were fabricated by a melt-mixing process which produced potentially self-healing composites with superior mechanical properties. By comparing peel testing, projectile testing, the quantitative healed strength, and other characteristics, it was determined that healing is not a function of the ionic content of the materials involved. Further, healing was determined to occur due to a synergy of thermomechanical properties facilitated by the addition of the methacrylic acid groups to the polymer backbone.
Master of Science

Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: Polymethacrylates are well known adhesives and can carry specific functionality, but have the disadvantage that their flexible backbones impart limited thermal stability and mechanical strength. Polyurethanes (PUs) are finding increasing application and use in many industries due to their advantageous properties, such as a wide range of flexibility combined with toughness, high chemical resistance and excellent weatherability. PUs do however have some disadvantages, for instance, PU is considered an expensive polymer, especially when considered for solvent based adhesives. the focus of this study was to consider a largely unstudied area of PU chemistry, namely combining PUs with polymethacrylates. Two types of linear urethane macromers (UMs) UM1 and UM2 were synthesized by the polyaddition polymerization of 4,4'-methylenediphenyl diisocyanate (MDI) with ethylene glycol (EG), and MDI with neopentylglycol (NPG), via a pre-polymer method, followed by termination with 2-hydroxy ethylacrylate (2-HEA) and methanol (MeOH) to yield UMs having specific urethane chain lengths, and which have to be predominantly monofunctional. Structural identification of the UMs was verified by MALDI-TOF-MS, FTIR, 13C-NMR and 1HNMR spectroscopy.Various percentages of the respective UMs (0_55 wt % of methacrylate monomers) were then incorporated into polymethyl methacrylate (PMMA) and poly n-butyl methacrylate (PnBMA) backbones via solution free-radical copolymerization. The resulting methyl methacrylate-g-urethane and n-butyl methacrylate-g-urethane copolymers were characterized by 1H-NMR,13C-NMR, FTIR, SEC with double detectors (UV and RI), light scattering, UV-Vis, HPLC, TGA, DSC, DMA and TEM. Weight percentages of UM incorporated into the methyl methacrylate-g-urethane copolymers were calculated using FTIR, UV-Vis and 1H-NMR techniques. Phase separation which occurred between the urethane segment and methacrylate segment in the graft copolymerization products was investigated by DMA, DSC and TEM analysis. Microphase separation occurred in all PMMA-g-UM1 and PnBMA-g-UM1 copolymers: two glass transitions temperatures corresponding to the PMMA or PnBMA and UM1 fractions, respectively, were observed. On the other hand, DMA and DSC results showed that in most graft copolymer products the two respective component parts PMMA-g-UM2 or PnBMA-g- UM2 were compatible, because only one Tg was observed. Two glass transitions occurred for PMMA or PnBMA and UM2 when the amount of UM was increased to 55 wt % during copolymerization and microphase separation was evident in DSC, DMA and TEM measurements. Thermal stability and storage modulus (stiffness) of all the synthesized PMMA-g-urethane and PnBMA-g-urethane copolymers increased as the concentration of urethane macromonomer in the copolymerization feed increased, as confirmed in TGA and DMA results. The surface and adhesive properties of the synthesized graft copolymer were studied by measuring the static contact angle and peel strength. Adhesion increased as the content of UMs increased in the graft copolymer. The graft copolymers prepared using a high UM2 feed for both PMMA and PnBMA showed improved in adhesion compared to the pure methacrylate polymers. The adhesion was better for both leather and for vinyl.
AFRIKAANSE OPSOMMING: Polimetakrilate is bekende kleefstowwe. Hulle het egter die tekortkoming dat hulle buigbare ruggraat beperkte termiese en meganiese stabliteit besit. Poliuretane (PUs) word deesdae al hoe meer gebruik in baie nywerhede as gevolg van hulle baie voordele, insluitend hul wye buigsaamheid tesame met sterkte, hoë chemiese weerstand en uitstekende weerbaarheid. PUs het egter ’n paar nadele: hulle is baie duur, veral wanneer hulle gebruik word in oplosmiddel-gebaseerde kleefstowwe. Die doel van hierdie studie is om die kombinering van PUs met polimetakrilate te bestudeer, 'n onderwerp wat tot dusver baie min aandag-getrek het. Twee tipes liniêre uretaanmakromere (UMs), UM1 en UM2, is gesintetiseer deur gebruik te maak van poliaddisiepolimerisasie van 4,4'-metileendifeniel diisosianaat (MDI) met etileenglikol (EG), en MDI met neopentielglikol (NPG), via ‘n prepolimeermetode, gevolg deur terminering met 2-hidroksiëtielakrilaat (2-HEA) en metanol (MeOH). Die produk hiervan is UMs met spesifieke kettinglengtes (hoofsaaklik monofunksioneel). Die samestelling van die UMs is met behulp van die volgende gevorderde analitiese tegnieke bepaal: MALDI-TOFMS, FTIR, 13C-NMR en 1H-NMR. Verskillende hoeveelhede van die UMs (0_55 gewIing% metakrilaatmonomere) is dan in die polimetielmetakrilaat (PMMA) en poli-n-butielmetakrilaat (PnBMA) ruggrate geïnkorporeer deur middel van oplossing-vryradikaalpolimerisasie. Die samestelling van die kopolimeerprodukte, metiel-metakrilaat-g-uretaan en n-butiel-metakrilaat-g-uretaan, is met behulp van die volgende gevorderde analitiese tegnieke bepaal: 1H-NMR, 13C-NMR, FTIR, SEC met dubbele detektors (UV en RI), ligverstrooiing UV-Vis, HPLC, TGA, DSC, DMA en TEM. Die hoeveelheid UM geïnkorporeer in die metielmetakrilaat-g-uretaan kopolimere is bereken deur gebruik te maak van FTIR, UV-Vis en 1H-NMR data. Die faseskeiding wat plaasgevind het tussen die uretaansegment en die metakrilaatsegment in die produkte van die entpolimerisasie is met behulp van DMA, DSC en TEM ondersoek. In alle PMMA-g-UM1 en PnBMA-g-UM1 kopolimere het mikrofaseskeiding plaasgevind: twee verskillende glasoorgangstemperature vir die PMMA of PnBMA en UM1 fraksies is waargeneem. Hierteenoor het DMA en DSC resultate getoon dat in die meeste entkopolimeerprodukte (PMMA-g-UM2 of PnBMA-g-UM2) was die twee komponente verenigbaar, aangesien net een Tg waargeneem is. In die geval van die kopolimere waar die hoeveelheid UM in die kopolimerisasiereaksies tot 55 gew% verhoog is, is twee glasoorgangstemperature vir PMMA of PnBMA, en UM2 waargeneem. Mikrofaseskeiding is met behulp van DSC, DMA en TEM bewys. Termiese stabiliteit en stoormodulus (styfheid) van alle gesintetiseerde PMMA-g uretaan en PnBMA-g-uretaan kopolimere het toegeneem namate die uretaankonsentrasie in die kopolimerisasiereaksie toegeneem het soos deur middel van TGA en DMA resultate bewys is. Die oppervlakte- en kleefeienskappe van die bereide entkopolimere is bestudeer deur die statiese-kontakhoek en skilkrag te meet. Adhesie het toegeneem namate die UMinhoud toegeneem het. Die entkopolimere berei met hoë PMMA en PnBMA inhoud het uiteindelik beter adhesie getoon as die suiwer metakrilaatpolimere. Die adhesie was beter vir beide leer en viniel.

Der Einsatz von organischen Materialien, insbesondere von Polymeren, hat zahlreiche Vorteile gegenüber dem Einsatz klassischer Materialien in der Mikroelektronik. Zu diesen zählen Flexibilität, geringes Gewicht, Verarbeitbarkeit durch Verfahren aus Lösung bei Raumtemperatur ohne Notwendigkeit vakuumbasierter Prozesse zur Abscheidung und vieles mehr. Dies ermöglicht eine energie- und kosteneffiziente Herstellung elektronischer Bauteile wie organische Feldeffekttransistoren (OFETs) oder Leuchtdioden (OLEDs), welche durch Prozesse wie dem Rolle-zu-Rolle-Druckverfahren nicht länger auf kleine Flächen begrenzt sind. Zur Herstellung polymerbasierter OFETs mit optimiertem Eigenschaftsprofil sind neben innovativen Halbleitern vor allem auch neue Dielektrika mit verbesserten elektrischen Eigenschaften erforderlich, zu deren Entwicklung die vorliegende Arbeit beitragen sollte. Das häufig verwendete Polymethylmethacrylat ist für den Einsatz als Gate-Dielektrikum für die organische und gedruckte Elektronik nur bedingt geeignet. Es zeigt einige Nachteile wie eine mangelnde Stabilität gegenüber bestimmten organischen Lösungsmitteln, was zu Quellung oder Anlösen des Dielektrikums während des Aufbringens weiterer Schichten führen kann. Durch Copolymerisation von Methylmethacrylat mit funktionalisierten Comonomeren sollten die Probleme gelöst und optimierte Methacrylat-Copolymere entwickelt werden. Die Copolymere wurden über freie radikalische sowie RAFT-Polymerisation synthetisiert. Allen gemeinsam sind vernetzbare Comonomere, um die Lösungsmittelstabilität zu verbessern und somit die Durchbruchfeldstärke des Dielektrikums zu erhöhen. Als Vernetzer wurden 4-Benzoylphenylmethacrylat (BPMA) oder Propargylmethacrylat (PgMA) gewählt. BPMA ist UV-vernetzbar, Copolymere mit PgMA können in Gegenwart von mehrfunktionalen Aziden wie 1,3,5-Tris(azidomethyl)benzen (TAMB) durch Click-Reaktion thermisch vernetzt werden. Ein weiterer Aspekt ist die Erhöhung der relativen Permittivität des Dielektrikums zur Steigerung der Kapazität der dielektrischen Schicht, wodurch unter anderem die Betriebsspannung des Transistors reduziert werden kann. Dieses Ziel sollte durch Komposite mit BaTiO3-Nanopartikeln erreicht werden. Zusätzlich zur Steigerung der Permittivität kann dies durch Verringerung der Filmdicke realisiert werden, was jedoch vermehrt zu Leckströmen führen könnte. Neben den dielektrischen Materialeigenschaften spielt vor allem auch die Grenzfläche zwischen Dielektrikum und Halbleiter eine wesentliche Rolle. Um die Interaktionen an dieser zu verbessern, wurden Comonomere mit selbstorganisierenden Seitenketten in die Polymerstruktur eingebracht. Die Kombination dieser Dielektrika mit chemisch angepassten Halbleitern mit vergleichbaren Seitenkettenfunktionalitäten soll dazu führen, dass die beiden Komponenten durch die Seitenketten verstärkt miteinander wechselwirken. Monomersynthesen sowie anschließende Copolymerisationen waren in hohen Ausbeuten und ausreichenden Molmassen bezüglich der Copolymere erfolgreich. Die strahleninduzierte Vernetzung konnte durch systematische Untersuchungen optimiert und die thermische Vernetzung bei moderaten Temperaturen nachgewiesen werden. Die Vernetzbarkeit von Copolymeren mit selbstorganisierenden Seitenketten erwies sich als gehindert. Hierfür wurde ein Vorschlag zur Erhöhung der Flexibilität der Vernetzerseitenkette unterbreitet. Für die Copolymere P(MMA/BPMA) und P(MMA/PgMA) konnten die Durchbruchfeldstärken in Folge der Vernetzung von < 0.3 MV/cm für PMMA auf bis zu mehr als 5 MV/cm gesteigert werden. BaTiO3-Nanopartikel konnten durch geeignete Methoden erfolgreich synthetisiert werden. Durch Variation der Reaktionsbedingungen war eine gezielte Steuerung der Primärpartikelgröße möglich. So wurden Partikel der Größe < 10 nm, 26 nm und 55 nm realisiert. Die Dispersion der Partikel in organischen Lösungsmitteln sowie in der Polymermatrix war stark abhängig von der Größe der Primärartikel, der Oberflächenmodifikation sowie der Neigung zur Agglomeration. Modifizierte Partikel mit einem Durchmesser < 10 nm konnten sehr gut in Lösungsmitteln wie auch in der Polymermatrix dispergiert werden (Abbildung 2). Eine Steigerung der relativen Permittivität der Nanokomposite blieb jedoch aufgrund der zu geringen Größe der Primärpartikel aus. Darüber hinaus wurden deutlich schlechtere Durchbruchfeldstärken beobachtet. Copolymere mit der Fähigkeit zur Selbstorganisation sollten durch zwei Konzepte realisiert werden. Im ersten System führte die Polymerisation von x-[4-(4´-Cyanophenyl)phenoxy]alkylmethacrylaten mit Spacerlängen von x = 6 und x = 8 nur in Homopolymeren zu ausgeprägter Selbstorganisation. Copolymere mit 50 mol% waren weitgehend isotrop und wiesen zudem ungenügende dielektrische Eigenschaften auf. Das zweite System basiert auf semifluorierten Methacrylat-Copolymeren mit H10F10-Seitenketten (10 CH2- und 10 CF2-Gruppen). Diese zeigten schon ab einem Gehalt von circa 35 mol% gute Selbstorganisation und bildeten ein geordnetes alternierendes Schichtsystem aus Haupt- und Seitenketten im Bulk und in dünnen Filmen. Die dielektrischen Eigenschaften können mit denen bekannter fluorierter Polymerdielektrika wie CYTOP konkurrieren. Damit stehen die semifluorierten Copolymere zukunftsorientiert zur Kombination mit Halbleitern, welche die gleichen Seitenkettenfunktionalitäten tragen, bereit, um so durch starke Interaktionen zwischen Dielektrikum und Halbleiter die Grenzfläche zu optimieren. Mit thermisch vernetztem P(MMA/PgMA) konnten OFETs mit den Halbleitern Pentacen bzw. C60 erfolgreich hergestellt und vermessen werden. Beide Transistoren liefern gute und mit Literaturwerten vergleichbare Kenngrößen. Die Ladungsträgermobilitäten und Ion/Ioff-Verhältnisse betragen 0.3 cm²/Vs und 6.0x10^5 im Pentacen-basierten Transistor beziehungsweise 1.3 cm²/Vs und 4.4x10^5 im OFET mit dem Halbleiter C60. Damit konnte in dieser Arbeit die Steigerung der Durchbruchfeldstärke durch geeignete Vernetzung der Copolymere realisiert werden. Die thermische Vernetzung fand bei deutlich geringeren Temperaturen als zahlreiche in der Literatur beschriebene Reaktionen statt. Die Synthese und Modifizierung von BaTiO3-Nanopartikeln und auch die Bildung entsprechender PMMA-BaTiO3-Nanokomposite war erfolgreich, führte jedoch nicht wie erwartet zu einer Steigerung der relativen Permittivität der Dielektrika-Schichten. Vernetzbare und selbstorganisierende semifluorierte Methacrylat-Copolymere konnten polymerisiert und charakterisiert werden und stehen als innovative dielektrische Materialien für Untersuchungen in OFETs zur Verfügung. Das Copolymer P(MMA/PgMA) wurde zielführend in organischen Feldeffekttransistoren eingesetzt und führte zu guten elektrischen Eigenschaften der Bauteile.

Thesis (MSc)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: Novel poly(methacrylic acid)-graft-poly(dimethylsiloxane) copolymers were synthesised by conventional free radical reactions using a poly(dimethylsiloxane) macromonomer. The polymers were electrospun to investigate how the fibre morphology can be modified by manipulating the electrospinning solution parameters, and to determine the possibility of using the polymers as new materials for the production of polymer nanofibre hydrogels. The electrospinning solution parameters were varied by electrospinning the highly amphiphilic copolymers in solvents with variable solvent qualities. Scanning Electron Microscopy (SEM) and Field Emission Scanning Electron Microscopy (FE–SEM) was used to investigate the fibre morphology. Internal morphology was studied using a freeze fracture technique prior to FE-SEM imaging. It is revealed that the polymers in this study does not form any fine structure or pores even when self-assembled structures are present in the solution. Attempts were made to visualise any self-assembled structures of films produced from dilute solutions using TEM. Further studies included investigating the fibres properties, primarily with regards to their rate and extent of moisture and water uptake. The fibres showed hydrogel behaviour and the PDMS content were found to have an impact on the hydrogel stability. Post electrospinning crosslinking of the nanofibres was also explored.
AFRIKAANSE OPSOMMING: Unieke ent-kopolimere wat bestaan uit poli(metielakrielsuur) (PMAS) en poli(dimetielsiloksaan) (PDMS) is gesintetiseer deur middel van 'n “ent-deur” vryeradikaalkopolimerisasie. 'n PDMS makromonomeer is vir hierdie doel gebruik. Die polimere is geëlektrospin om vesels te vorm. Die doel was om die invloed van verkillende strukture in oplossing op die veselmorfologie te bepaal. Die moontlikheid om hierdie nanovesels as gels te gebruik is ook ondersoek. Die amfifiliese kopolimere is geëlektrospin uit die oplossing waarin dit wisselende oplosbaarheid toon. Skandeer elektron mikroskopie (SEM) is gebruik om die morfologie te ondersoek. Die interne morfologie van die vesels is ondersoek deur die vesels te vries en in die gevriesde toestand te breek. Die studie het getoon dat geen strukture op, of binne, die vesels vorm nie, selfs al moes daar assosiasie tussen segmente van die polimere gewees het. Hierdie tipe assosiasies sou strukture in die oplossing tot gevolg gehad het. 'n Poging is aangewend om die strukture in oplossing te visualiseer deur transmissie elektron mikroskopie (TEM) van dun films te ondersoek. Films is vanaf verdunde oplossings gevorm. Ander studies het ingesluit om die eienskappe van die vesels te ondersoek, met die fokus op hoeveel en hoe vinnig die vesels waterdamp en water kon absorbeer. Die vesels het soos 'n gel reageer. Hierdie gedrag is beïnvloed deur die hoeveelheid PDMS wat 'n definitiewe invloed op die stabiliteit van die gel gehad het. Kruisverbindings van die vesels, nadat dit geëlektrospin is, is ook ondersoek.

Ces travaux décrivent la synthèse de nanoparticules stabilisées par des polyélectrolytes d’originesynthétique (poly(acide (méth)acrylique)) ou naturelle (alginate) par polymérisation radicalairecontrôlée (PRC) de type RAFT en émulsion. Ce procédé est basé sur l’utilisation d’un polymèrehydrophile obtenu par RAFT (macroRAFT) qui est réactivé dans l’eau pour la polymérisation d’unmonomère hydrophobe. Des copolymères à blocs amphiphiles sont ainsi générés et s’auto-assemblent in situ pour former des nanoparticules. Dans un premier temps, nous avons cherché à conduire l’ensemble du procédé en milieu aqueux. Des études ont ainsi été menées sur la polymérisation RAFTdans l’eau de l’acide acrylique et de l’acide méthacrylique. Des homopolymères bien définis ont été obtenus sur une large gamme de conditions, puis ont été utilisés comme macroRAFTs pour la polymérisation en émulsion de monomères hydrophobes. Des nanoparticules stables constituées de copolymères à blocs amphiphiles bien définis ont été produites. Il a été montré que le contrôle de la polymérisation et la nucléation dépendaient fortement du pH, mais qu’une bonne stabilité colloïdale était néanmoins observée dans tous les cas. Ce procédé "one-pot " a ensuite été extrapolé à la synthèse de particules stabilisées par des copolymères hydrophiles de N-acryloylmorpholine (NAM) et de macromonomères d’alginate. Des nano-objets aux morphologies variées ont été obtenus. Afin de mieux appréhender la formation de ces morphologies, un système modèle employant un copolymère hydrophile de NAM et de macromonomère de polyNAM obtenu par polymérisation RAFT a été étudiépour la polymérisation en émulsion du styrène
This work describes the synthesis of nanoparticles stabilized by polyelectrolytes from synthetic(poly((meth)acrylic acid)) or natural (alginate) source by controlled free radical polymerization (CRP),namely RAFT, in emulsion. This process is based on the use of a hydrophilic polymer prepared by RAFT (i.e. macroRAFT) which is reactivated in water for the polymerization of a hydrophobic monomer. The formation of amphiphilic block copolymers which self-assemble in situ leads to the formation of nanoparticles. Firstly, we tried to perform the whole process in water. The RAFT polymerization of acrylic acid and methacrylic acid was studied in this context. Well-defined homopolymers were obtained under a large range of conditions, and further used as macroRAFTs in emulsion polymerization of hydrophobic monomers. Stable nanoparticles composed of well-defined amphiphilic block copolymers were produced. It was shown that the control of the polymerization and the nucleation were strongly dependent on the pH. Nevertheless, a good colloidal stability wasobserved in all cases. This “one-pot” process was then extrapolated to the synthesis of particles stabilized by hydrophilic copolymers of N-acryloylmorpholine (NAM) and alginate macromonomer. Nano-objects with various morphologies were obtained. In order to better understand the formation of these morphologies, a model system using a hydrophilic copolymer of NAM and a polyNAM macromonomer obtained by RAFT polymerization was studied in styrene emulsion polymerization

Des polymères à base de méthacrylate de poly(oxyde d'éthylène) (PEOMA) avec des chaînes pendantes PEO (Mn = 300 ou 950 g mol-1) ou des copolymères de PEOMA300 et d'acide méthacrylique (AMA) ont été synthétisés par polymérisation radicalaire contrôlée par les nitroxydes en utilisant une alkoxyamine (BlocBuilder®) comme amorceur en présence de SG1 et d'une faible quantité de styrène. Les copolymères à base de PEOMA300 et d'AMA sont thermo- et pH-sensibles. Les deux types de macroalkoxyamines ont été utilisés pour amorcer la copolymérisation en émulsion du méthacrylate de n-butyle et du styrène et former, par auto-assemblage induit par la polymérisation, des particules composées de copolymères à blocs amphiphiles, en absence ou présence de particules de silice. En absence de silice, des particules stabilisées de façon stérique ou électrostérique ont été formées. La polymérisation présente les caractéristiques d'une polymérisation contrôlée avec néanmoins la formation d'une faible proportion de chaînes mortes. L'effet du pH, de la force ionique et de la nature ou de la concentration des macroalkoxyamines sur la cinétique de polymérisation et la morphologie des particules a été étudié, et des sphères, des vésicules ou des nanofibres ont été obtenues. Les macroalkoxyamines à base de PEO s'adsorbent sur la silice via la formation de liaisons hydrogène entre les chaînes PEO et les groupes silanol. La synthèse de copolymères à blocs en surface de la silice a conduit à la formation de particules hybrides de différentes morphologies (bonhomme de neige, multipodes, framboise, coeur-écorce, têtard, mille pattes) liées à la taille de la silice, au pH et à la nature du macroamorceur
Water-soluble brush-type polymers composed of poly(ethylene)oxide methacrylate (PEOMA) units with PEO side groups of various chain lengths (Mn = 300 and 950 g mol-1) or of PEOMA300 with methacrylic acid (MAA) were synthesized by nitroxide-mediated polymerization using an alkoxyamine initiator (BlocBuilder®) and SG1 nitroxide in the presence of a low amount of styrene. The PEOMA300-MAA based copolymers showed a dual temperature/pH response. The two series of macroalkoxyamines were used in aqueous emulsion copolymerization of nbutyl methacrylate and styrene leading to the formation of particles composed of amphiphilic block copolymers through polymerization-induced self-assembly, in both the absence and presence of silica. The experiments performed in the absence of silica particles resulted in the formation of sterically or electrosterically stabilized latexes. The polymerization exhibited all the features of a controlled system with however the presence of a small proportion of dead chains. The effect of pH value, ionic strength and type and concentration of the macroalkoxyamine initiator on polymerization kinetics and latex morphologies was investigated. Depending on the reaction conditions, spherical particles, vesicles or nanofibers were successfully prepared. The PEO-based macroalkoxyamines were shown to adsorb on the silica surface via hydrogen bond interaction between PEO and the silanol groups. This enabled block copolymers to be generated in situ on the silica surface leading to hybrid particles with snowman, raspberry, daisy, core-shell, “tadpole-” and “centipede-” like morphologies depending on the silica particle size, pH value and type of macroinitiator

碩士
國立中央大學
化學工程學系
84
Abstract The major purpose of this study is familiar with group transfer polymerization (GTP) and tried to synthesize diblock copolymer by GTP. For our synthesis experiment ,we elected to use methyl ethacrylate(MMA) and dimethylaminoethyl methacrylate (DMAEMA). At first, research the effect of residuary reactant initiator on polymerization. Then research the effect of reaction conditions on polymerization. The results show the obvious increase of molecular weight and molecular weight distribution as initiator includes a little n-butyllithium,lithium diisopropylamine and trimethylchlorosiline in polymerization reaction. If initiator includes a little diisopropylamine,methyl isobutyrate,diether etheranhydrous,it has no effect for molecular weight and molecular weight distribution. GTP polymerization is an exothermic reaction，it shows reaction end point as reaction temperature decreases to the original point，and molecular weight and molecular weight distribution have no more variation. Initiator quantity gets inverse ratio to molecular weight，but it has no effect to molecular weight distribution. It can proceed reaction in the allowable concentration ratio of catalyst and initiator，molecular weight distribution will increase as catalyst uses much more than it needs. It can proceed reaction in the allowable temperature range，the temperature has no effect to molecular weight and molecular weight distribution. This experiment of GTP method can polymerize the block copolymer of narrow molecular weight distribution. Keywords:group transfer polymerization(GTP), block copolymer, methyl methacrylate, dimethylaminoethyl methacrylate,

碩士
臺灣大學
高分子科學與工程學研究所
98
The unique and tunable fluid properties of supercritical carbon dioxide have been used in polymer synthesis or polymer process recently, especially, the materials for medical, pharmaceutical, and food technology. In this work, polymeric antioxidants were synthesized for the first time in supercritical carbon dioxide. The strategy that using supercritical carbon dioxide as green solvent, methacrylic acid(MAA) as monomer, antioxidant ferulic acid(FA) as comonomer and ethylene glycol dimethacrylate (EGDMA) as crosslinker is suggested, and addition polymerization proceeded with initiator AIBN under supercritical carbon dioxide (65℃, 20 MPa, 24 hrs). The two forms of polymeric antioxidants, linear copolymer PMAA-FA and network polymer PMAA-FA-EGDMA, were obtained successfully. The chemical properties could be identified by FTIR, UV-Vis spectrums and 1H NMR, and the degradation temperature of polymeric antioxidants were studied by TGA. Antioxidant ability measured by DPPH assay of PMAA-FA and PMAA-FA-EGDMA performed about 89.4 % and 72.9 %. Compared with that of the control polymers synthesized in the absence of antioxidant molecules, the antioxidant activity of the two polymeric antioxidants was effectively elevated. SEM images showed the size of products were about 0.24~0.49 μm with aggregated morphology. The two forms of polymeric antioxidants could be useful in pharmaceutical and medical applications.