Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: This study describes the synthesis and self-assembly of hetero-arm molecular brushes (hetero-arm MBs). These MBs consist of two polymeric side chains (SCs) of different natures, alternatingly distributed along the main chain (backbone). Two different types of hetero-arm MBs were prepared: first, alternating amphiphlic hetero-arm MBs (AMBs), and second, alternating hetero-arm MBs (AHMBs). Hetero-arm AMBs were synthesized via two strategies: (I) via a combination of “grafting through” and “grafting onto”, and (II) via “grafting through”. In approach (I), poly[vinyl benzyl (polyethylene glycol)-alt-N-alkyl-maleimide)] (poly[VB-(PEG12)-alt-N-(CnH2n+1)-MI]) was prepared via radical copolymerization of vinyl benzyl-terminated polyethylene glycol (VB-PEG12) with maleic anhydride (MAnh) (grafting through), which produces graft copolymers with PEG SCs and reactive succinic anhydride repeat units alternatingly distributed along the backbone. These graft copolymers were then modified by nucleophilic substitution (imidization) with alkyl amines (CnH2n+1-NH2) on the succinic anhydride residues (grafting onto). Three different primary amines possessing different alkyl chain lengths (n = 4, 12 and 16) were used in the modification process. In this way, hetero-arm AMBs with different hydrophilic to hydrophobic ratios were obtained. In approach (II), similar hetero-arm AMBs were prepared in a one-step grafting through approach. In this case, poly[VB-(PEG17)-alt-N-(CnH2n+1)-MI] (n = 10, 16 and 20) was prepared via radical copolymerization of VB-PEG17 with N-dodecylmaleimide, N-hexadecylmaleimide and N-icosylmaleimide. Following the synthesis step, self-assembly of these hetero-arm AMBs in arm-selective solvents was investigated in relation to the alkyl chain length. The morphology of the obtained assemblies was characterized by Field Emission gun-Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy (TEM) and Fluorescence Microscopy (a fluorescent dye was encapsulated). Cylindrical-like aggregates, length 10 μm and diameter ~ 250 nm, were obtained upon hetero-arm AMBs self-assembly. The second type of hetero-arm MBs was hetero-arm AHMBs, in which the SCs consist of PEG and poly(N,N-dimethylamino-ethyl methacrylate) (PDMAEMA). These hetero-arm AHMBs were prepared via a combination of grafting through and grafting from approaches. In this case, poly[vinyl benzyl-(polyethylene glycol)-alt-N-(poly(N,N-dimethylamino-ethyl methacrylate) maleimide] (poly[VB-(PEG17)-alt-N-(PDMAEMA)-MI) was prepared in the following steps: (1) alternating poly[vinyl benzyl-(polyethylene glycol)-alt-N-(4-hydroxyphenyl) maleimide] (poly[VB-(PEG17)-alt-N-(HPh)-MI]) was synthesized via radical copolymerization of VB-PEG17 with N-(4-hydroxyphenyl) maleimide (N-HPhMI). (grafting through), (2) the hydroxyl sites were esterified with 2-bromoisobutyryl bromide to afford poly [vinyl benzyl-(polyethylene glycol)-alt-N-(4-(2-bromobutyryloxy)phenyl) maleimide] (poly[VB-(PEG17)-alt-N-(BrPh)-MI]) (macroinitiator) and (3) an atom transfer radical polymerization (ATRP) reaction of 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA) was initiated from the obtained macroinitiator. This approach afforded poly[VB-(PEG17)-alt-N-(PDMAEMA)-MI] hetero-arm AHMBs with two water soluble SCs; however, one is water soluble at all pHs and temperatures (i.e. PEG), while the other is a pH- and temperature-sensitive polymer (i.e. PDMAEMA). Initial attempts were made to fabricate cylindrical organo/silica hybrid materials based on these AMHBs as the organic template and tetra-ethylorthosilicate as the silica precursor. Preliminary results indicate the formation of silica nano-wires, ~ 8 μm in length and ~45 nm in diameter. The self-assembly behavior of these AHMBs in water at a temperature above the lower critical solution temperature of PDMAEMA (> 55 °C) was also investigated. Fibril morphology (~ 30 nm in diameter) was observed. This study addresses initial attempts to fabricate organic/inorganic hybrid materials with controlled size and morphologies via densely grafted hetero-arm molecular brushes. / AFRIKAANSE OPSOMMING: Hierdie studie beskryf die sintese en selfsamestelling van prototipe molekulêre borsels (prototipe MBs). Hierdie MBs bestaan uit twee polimeriese sykettings (SKs) van verskillende aard wat afwisselend langs die hoofketting (ruggraat) voorkom. Twee verskillende tipes van die prototipe MBs is gesintetiseer: eerstens, afwisselende amfifiliese prototipe MBs (AMBs), en tweedens, afwisselende hetero-arm prototipe MBs (AHMBs). Prototipe AMBs is gesintetiseer d.m.v. twee strategieë: (I) deur 'n kombinasie van „enting deur‟ en „enting aan‟ benaderings, en (II) deur middel van „n „enting deur‟ benadering. In benadering (I) is poli[vinielbensiel(poliëtileenglikol)-alt-N-alkiel-maleïenamied)] (poli[VB-(PEG12)-alt-N-(CnH2n+1)-MI]) gesintetiseer deur radikaalkopolimerisasie van vinielbensiel-beëindigde-poliëtileenglikol (VB-PEG12) met maleïenanhidried („enting deur‟) wat entkopolimere produseer met PEG SKs en reaktiewe suksienanhidried herhaaleenhede wat afwisselend langs die ruggraat versprei is. Daarna is die entkopolimere gewysig d.m.v. nukleofiliese substitusie (imiedisering) met alkielamiene (CnH2n+1-NH2) op die oorblywende suksienanhidried („enting op‟). Drie verskillende primêre amiene met verskillende alkielkettinglengtes (n = 4, 12 en 16) is gebruik vir die wysigingsproses. So is prototipe AMBs met verskillende hidrofiliese tot hidrofobiese verhoudings verkry. In benadering (II) is soortgelyke prototipe AMBs gesintetiseer in 'n een-stap „enting deur‟ benadering. In hierdie geval is poli[VB-(PEG17)-alt-N-(CnH2n+1)-MI] (n = 10, 16 en 20) gesintetiseer d.m.v. radikaalkopolimerisasie van VB-PEG17 met N-dodesiel maleïenamied, N-heksadesiel maleïenamied en N-ikosiel maleïenamied. Na afloop van die sintese stap is die selfsamestelling van hierdie prototipe AMBs in spesifieke oplosmiddels in verhouding tot die alkielkettinglengtes ondersoek. Die morfologie van die versamelings is gekarakteriseer deur veld-emissie-geweer-(Eng: field emission gun-)-skandeerelektronmikroskopie (FE-SEM), transmissie-elektronmikroskopie (TEM) en fluoresserende mikroskopie („n fluoresserende kleurstof is ingesluit). Silinderagtige versamelings (lengtes ~10 μm en deursnee ~250 nm) is deur die selfsamestelling van prototipe AMBs verkry. Die tweede soort prototipe MBs is prototipe AHMB, waarin die SKs uit PEG en poli(N,N-dimetielaminoetiel metakrilaat) (PDMAEMA) bestaan. Hierdie prototipe AHMBs is d.m.v. 'n kombinasie van „enting deur‟ en „enting van‟ benaderings gesintetiseer. In hierdie geval is poli[vinielbensiel-(poliëtileenglikol)-alt-N-(poli(N,N-dimetielaminoetiel metakrilaat) maleïenamied] (poli[VB-(PEG17)-alt-N-(PDMAEMA)-MI) gesintetiseer deur van die volgende stappe gebruik te maak: (1) sintese van afwisselende poli[vinielbensiel-(poliëtileenglikol)-alt-N-(4-hidroksifeniel) maleïenamied] (poli[VB-(PEG17)-alt-N-(HPh) -MI) deur midel van radikaalkopolimerisasie van VB-PEG17 met N-(4-hidroksifeniel) maleïenamied (N-HPhMI) („enting deur‟), (2) esterifikasie van die hidroksielgroepe met 2-bromoisobutiriel bromied om poli[vinielbensiel-(poliëtileenglikol)-alt-N-(4-(2-bromobutirieloksi) feniel) maleïenamied] (poli[VB-(PEG17)-alt-N-(BrPh)-MI]) (makro-afsetter) te berei, en (3) die atoomoordrag-radikaalpolimerisasie reaksie van 2-(N,N-dimetielamino)etiel metakrilaat (DMAEMA) wat begin is vanaf die gevormde makro-afsetter. Hierdie benadering gee poli[VB-(PEG17)-alt-N-(PDMAEMA)-MI] prototipe AHMBs met twee wateroplosbare SKs, waarvan een wateroplosbaar is by alle pHs en temperature (d.w.s. PEG), terwyl die ander tipe SK „n pH- en temperatuur-sensitiewe polimeer is (d.w.s. PDMAEMA). Aanvanklike pogings is aangewend om silindriese organo/silika hibriedmateriale te sintetiseer, gebaseer op hierdie AHMBs as die organiese segment en tetraëtielortosilikaat as die silika voorloper. Die voorlopige resultate dui op die vorming van silikananodrade, lengte ~8 μm en deursnit ~45 nm. Die selfsamestellingsgedrag van hierdie AHMBs is ook in water ondersoek by 'n temperatuur hoër as die laer kritieke oplossingstemperatuur van PDMAEMA (> 55 °C). „n Draadagtige morfologie (deursnit ~30 nm) is waargeneem. Hierdie studie beskryf aanvanklike pogings om organiese–anorganiese hibriedmateriale met beheerde groottes en morfologieë via dig-geënte hetero-arm molekulêre borsels te vervaardig.

Cellulose is the most abundant renewable polymer on the planet and there is great interest in expanding its use beyond its traditional applications. However, its hydrophilicity and insolubility in most common solvent systems are obstacles to its widespread use in advanced materials. One way to counteract this is to attach hydrophobic polymer chains to cellulose: this allows the properties of the copolymer to be tailored by the molecular weight, density, and physical properties of the grafts. Two methods were used here to synthesize the graft copolymers: a ‘grafting-from’ approach, where synthetic chains were grown outward from bromoester moieties on cellulose (Cell-BiB) via Cu(0)-mediated polymerization; and a ‘grafting-to’ approach, where fully formed synthetic chains with terminal sulfide functionality were added to cellulose acetate with methacrylate functionality (CA-MAA) via thiol-ene Michael addition. The Cell-BiB was synthesized in the ionic liquid 1-butyl-3-methylimidazolium chloride and had a degree of substitution of 1.13. Polymerization from Cell-BiB proceeded at similar but slightly slower rate than an analogous non-polymeric initiator (EBiB). The average graft density of poly(methyl acrylate) chains was 0.71 chains/ring, with a maximum of 1.0 obtained. The graft density when grafting poly(methyl methacrylate) was only 0.15, and this appeared to be due to the slow initiation of BiB groups. Using EBiB to model the reaction and improve the design should allow this to be overcome. Chain extension experiments demonstrated the living behaviour of the polymer. The CA-MAA was synthesized by esterification with methacrylic acid. Reactions of CA-MAA with thiophenol and dodecanethiol resulted in quantitative addition of the thiol to the alkene. The grafts were synthesized by Cu(0)-mediated polymerization from a bifunctional initiator containing a disulfide bond, followed by reduction to sulfides. The synthetic polymers were successfully grafted to CA-MAA but the grafting yield was limited by the low sulfide functionality. Better retention of sulfide functionality is necessary for more efficient grafting. / Thesis (Master, Chemical Engineering) -- Queen's University, 2013-05-27 16:21:03.874

The addition of isocyanates to C=N double bonds of imines gives triazindione heterocycle structures; their thermal properties are reported. Mono-isocyanates were used to form 2:1 adducts with the imine bases 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) and 2-tert-butyl-1,1,3,3-tetramethylguanidine (tBuTMG). A 2:1 stoichiometry of the adducts was proven by NMR and IR spectroscopy, and single crystal X-Ray diffraction; certain cleavage temperatures (70 and 160 °C) were measured. Thermal analysis (TG-MS) of adducts indicates the release of free isocyanate during adduct cleavage. Furthermore, a new class of step-growth oligomers (MN = 750–7,000 g∙mol–1) composed of multi-functional isocyanates and these imine bases was introduced. Their systematic spectroscopic and thermal analysis is shown revealing the similarity in their chemical properties to the 2:1 adducts. Radical homo- and copolymerization of acrylates is initiated by the meta-stable adducts and oligomers of this work; the generation of novel telomeric block-copolymer architectures composed of polyacrylate and oligourea building blocks is demonstrated. / Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Plusieurs mécanismes de polymérisation radicalaire contrôlée (PRC) sous irradiation lumineuse ont récemment été développés. Ces approches offrent potentiellement de nombreux avantages, en permettant notamment d’introduire dans le mécanisme des PRCs certaines caractéristiques propres aux photopolymérisations, tels que les contrôles spatial et temporel de la réaction. Les travaux de thèse présentés dans ce manuscrit s’inscrivent dans ce contexte, en ayant pour objectif le développement et l’étude d’un nouveau mécanisme de polymérisation radicalaire par transfert d’atome (ATRP) photocatalysée. Après une étude bibliographique présentant l’état de l’art dans le domaine des PRCs sous irradiation lumineuse (chapitre 1), un complexe de bis(1,10-phenanthroline) cuivre (I) (Cu(I)) est utilisé comme catalyseur pour la synthèse de poly(méthacrylate de méthyle)s bien définis par ATRP menée sous l’irradiation d’une lampe LED bleue de faible intensité (chapitre 2). Le mécanisme proposé implique la formation de l’état excité Cu(I)* à partir de Cu(I) sous irradiation, suivie de sa désactivation oxydative par les composés bromés, générant les espèces actives propagatrices et la forme désactivante du complexe Cu(II). Le cycle catalytique est ensuite complété par l’ajout de triethylamine comme agent réducteur permettant la régénération in situ de la forme activante Cu(I) du complexe et conduisant ainsi à une polymérisation plus rapide. Le méthacrylate de glycidyle est ensuite considéré comme comonomère jouant simultanément le rôle d’un agent réducteur (chapitre 3). Des copolymères fonctionnels bien définis, avec une distribution contrôlée de groupes latéraux époxydes, sont ainsi synthétisés. Enfin, le mécanisme d’ATRP photocatalysé est amélioré en développant une procédure permettant la génération in situ de la forme activante Cu(I) en partant d’un complexe Cu(II) stable en présence d’air (chapitre 4). Le mécanisme ainsi développé présente une bonne tolérance à la présence d’oxygène ou d’inhibiteur dans le milieu réactionnel. Les effets de plusieurs paramètres (intensité lumineuse, concentration en ligand et nature du solvant ou du contre-ion) sont étudiés, suggérant un échange de ligand photo-induit comme processus photochimique additionnel impliqué dans le mécanisme d’ATRP photocatalysé étudié. / Several mechanisms of controlled radical polymerization (CRP) under light irradiation have been recently developed. These approaches offer potentially numerous advantages, enabling especially to introduce in the mechanism of CRPs some features characteristic of photopolymerizations, such as the spatial and temporal controls of the reaction. The PhD work presented in this manuscript comes in this framework, aiming at developing and studying a new mechanism of photocatalyzed atom transfer radical polymerization (ATRP). After a bibliographic study presenting the state-of-the-art in the domain of CRPs under light irradiation (chapter 1), a bis(1,10-phenanthroline) copper (I) complex (Cu(I)) is used as catalyst for the synthesis of well-defined poly(methyl methacrylate)s by ATRP carried out under the irradiation of a low intensity blue LED lamp (chapter 2). The proposed mechanism implies the formation of the excited state Cu(I)* from Cu(I) under irradiation, followed by its oxidative quenching by the brominated compounds, generating the growing active species and the deactivator form of the complex Cu(II). The catalytic cycle is then completed by the addition of triethylamine as a reducing agent enabling the in situ regeneration of the activator form of the complex Cu(I), therefore leading to a faster polymerization. Glycidyl methacrylate is then considered as a comonomer playing simultaneously the role of a reducing agent (chapter 3). Well-defined functional copolymers, with a controlled distribution of epoxide side groups, are thus synthesized. Finally, the photocatalyzed ATRP mechanism is improved by developing a procedure permitting the in situ generation of the activator Cu(I) starting directly from an air-stable Cu(II) complex (chapter 4). The mechanism developed in this way exhibits a good tolerance to the presence of oxygen or inhibitor in the reaction medium. The effects of several parameters (light intensity, ligand concentration and nature of the solvent or counter-ion) are studied, suggesting a photo-induced ligand-exchange as an additional photochemical process implied in the studied photocatalyzed ATRP mechanism.

Les problématiques et potentialités de la photopolymérisation radicalaire en miniémulsion ont été discutées, en partant de l’étude des propriétés optiques des miniémulsions de monomère jusqu’à la synthèse de nouvelles nanoparticules polysulfures semi-cristallines par réaction thiol-ène. En premier lieu, l'interaction entre les propriétés optiques de miniémulsion de monomère et l'efficacité de photopolymérisation a été clarifiée. Nous avons établi le rôle majeur de la diffusion optique sur les cinétiques de photopolymérisation de nanogouttelettes acrylates, tandis que l'absorption s’est révélé de moindre importance. Que ce soit en milieu dilué ou concentré (modèle de Kubelka-Munk), la diffusion de la lumière est atténuée lorsque la taille de gouttelettes diminue. La conséquence immédiate est une amélioration significative de la pénétration de la lumière induisant une accélération des cinétiques de polymérisation. Néanmoins, cette conclusion doit être pondérée car l’effet de compartimentage de la polymérisation radicalaire n’a pu être dissocié des effets optiques. On notera qu’en milieu concentré (contenu en solide de 30 % massique), au-delà de 150 nm pour le diamètre de gouttelette, le coefficient de diffusion atteint un palier et devient indépendant de la taille des gouttelettes. La chute d’absorbance, observée par spectroscopie UV-visible, tout au long de l’irradiation pour des miniémulsions acrylates de faible taille (40 nm) a mis en évidence un mécanisme de polymérisation par diffusion de monomère des gouttelettes non nucléées vers les particules en croissance. Cette analyse non invasive (aucune dilution n’a été nécessaire) présente un intérêt évident pour l’étude du mécanisme de nucléation. Nous avons ensuite démontré que la photopolymérisation pouvait être réalisée en utilisant le caractère auto-amorçant des acrylates sous irradiation UV court ( < 300 nm). Ce type d’amorçage photochimique a permis d’éviter l’emploi de photoamorceur, limitant ainsi les risques liés à leur présence résiduelle dans le matériau final. Les photopolymérisations ont été réalisées dans un microréacteur modèle (cuve spectroscopique d’épaisseur 0,1 à 1 mm). La variation de plusieurs paramètres expérimentaux a permis d’identifier un ensemble de paramètres clés influençant les cinétiques de polymérisation tels que la taille des gouttelettes, corroborant ainsi les résultats de l’étude optique. Les longueurs d’onde d’irradiation et le chemin optique ont joué un rôle tout aussi déterminant ; le décalage vers des longueurs d’onde courtes et la diminution de l’épaisseur de l’échantillon accélèrent à la fois la création de radicaux amorceurs et le nombre d’entités nucléées. La versatilité du procédé a été démontrée en polymérisant rapidement (conversion totale en moins de 20 min) une large gamme de monomères acrylate, méthacrylate ou à base d’acétate de vinyle. En ce qui concerne le mécanisme d’auto-amorçage, nous avons prouvé que les espèces amorçantes provenaient vraisemblablement d’un biradical photoinduit, pouvant arracher ou transférer un hydrogène sur des molécules de monomère pour former des monoradicaux amorceurs. Par le biais de ce mécanisme original, la génération de radicaux est constante tout au long de la polymérisation ce qui pour effet d’impacter les caractéristiques des copolymères formés : l’indice de polymolécularité tend à augmenter et les masses molaires à diminuer par rapport à un processus photoamorcé conventionnel. Ces photopolymérisations ont été réalisées dans un photoréacteur annulaire à immersion et ont montré les mêmes évolutions en fonction de la taille de gouttelettes que lors d’expériences en cuve spectroscopique non agitées. A titre d’exemple, une conversion totale est atteinte en 1 h pour des tailles de gouttelettes de 60 nm et un contenu en solide de 30 %. L’auto-amorçage photoinduit a permis de générer rapidement une grande quantité de chaînes en croissance au sein des gouttelettes. [...] / Issues and potentials of miniemulsion radical photopolymerization were discussed, starting from monomer miniemulsions’ optical properties to the synthesis of new semi-crystalline polysulfide nanoparticles by thiol-ene reaction. First, the relationship between the optical properties of miniemulsion and the polymerization efficiency was clarified. We established the major role of optical scattering on the acrylate nanodroplets’ photopolymerization kinetic, while the absorption was found to play a minor role. Whether diluted or concentrated medium (Kubelka-Munk model), light scattering is attenuated when droplet size decreased. The corollary is a significant improvement of UV light penetration within the reactor vessel leading to an acceleration of the polymerization kinetics. However, this conclusion was mitigated by the fact that compartmentalization effect could not be easily dissociated from optical effects. Note that in concentrated medium (solids content of 30 wt %), beyond 150 nm droplet diameter, the scattering coefficient leveled off regardless of droplet size. An absorbance drop was observed using UV-visible spectroscopy throughout the irradiation of the smallest acrylate miniemulsions (40 nm). This result suggested a polymerization mechanism occurring by monomer diffusion from non-nucleated droplets to growing particles. This non-invasive analysis (no dilution was required) is of high interest to study the nucleation mechanism.In a second part, we demonstrated that acrylate miniemulsion photopolymerization could be performed through a monomer self-initiation mechanism induced by short-wavelength UV irradiation ( < 300 nm). Such original photochemical initiation avoided the use of photoinitiator, thus limiting the risks associated with their residual presence in the final material. The self-initiated photopolymerizations were carried out in a model microreactor (spectroscopic cell of 0.1 to 1 mm thick). The variation of several parameters allowed us to identify key parameters influencing polymerization kinetics such as droplet size, thus corroborating the results of the optical study. The irradiation wavelength and the optical path played a crucial role; the shift towards shorter wavelengths and the sample thickness reduction accelerated both the generation of initiating radicals and the number of nucleated entities. The versatility of the method was demonstrated by fast polymerization (complete conversion achieved within 20 minutes) employing a wide range of acrylate, methacrylate and vinyl acetate monomers. Regarding the self-initiating mechanism, one proved that the initiating species likely originated from a biradical able to abstract or transfer hydrogen from monomer molecules, thereby forming initiating monoradicals. Through this original mechanism, the generation of radicals was constant throughout the polymerization, which impacted the characteristics of the copolymer chains: the polydispersity index tended to increase and the molar masses decreases when compared with a conventional photoinduced process. These photopolymerizations were also carried out in an annular immersion photoreactor and showed the same trends regarding the effect of droplet size as the experiments conducted in unstirred spectroscopic tank. For example, a complete conversion was reached after 1 h for a 60 nm acrylate miniemulsion with a solids content of 30 wt %. As a result, a self-initiated polymerization can generate rapidly a large amount of insoluble growing polymer chains within the droplets. This unique feature was exploited to overcome Ostwald ripening without the addition of a specific costabilizer. Photochemical self-initiation could also be used to form surfactant-free nanolatex via Pickering-stabilized miniemulsion photopolymerization. Indeed, Laponite clay adsorbed at the surface of the droplets showed an excellent UV transparency up to 200 nm. [...]

Les synthèses de polymérisation assistées par micro-ondes sont reconnues pour réduire les temps de chauffe et améliorer des rendements en comparaison à celles effectuées sous chauffage conventionnel. Cette technique étant limitée par la profondeur de pénétration des micro-ondes, un dispositif millifluidique en continu couplé à l’irradiation micro-onde a été développé et étudié. Dans ce travail, une étude des réactions de polymérisation et de copolymérisation d’un couple de monomères (acide acrylique et styrène sulfonate de sodium) a été réalisée. Ces polymères ont été synthétisés par polymérisation radicalaire en réacteur discontinu ouvert sous chauffage conventionnel et sous irradiation micro-ondes dans un premier temps. Dans une seconde partie, ces polymères ont été synthétisés dans un dispositif millifluidique sous chauffage conventionnel et sous irradiation micro-onde. Enfin une dernière partie concerne l’étude de ces synthèses en millifluidique micro-ondes, pour cela un nouveau dispositif, associant micro-ondes et procédé fluidique, a été développé. Un nouvel outil de lecture de la température a été mis en place et l’utilisation d’une sonde chimique interne a été validée. Des synthèses de (co)polymères ont été réalisées et les résultats en termes de cinétiques comparés aux systèmes précédents. / Assisted microwave polymerization syntheses are known to reduce heating time and to improve yields as compared to the syntheses conducted under conventional heating methods. Nevertheless, this technique is limited by the penetration depth of microwaves. Within this work, a millifluidic device coupled to the microwaves irradiation has been developed and studied.Polymerization and copolymerization reactions of both monomers, acid acrylic and sulfonated styrene, were carried out. First, these polymers were synthesized by radical polymerization in a batch reactor under conventional heating and under microwaves irradiation. Secondly, these polymers have been synthesized and compared in a millifluidic device under conventional heating and under microwave irradiation. At last, a specific device has been developed to do the polymerization in millifluidic condition and under microwaves irradiation. A new tool for reading the temperature inside this system was implemented and the use of a chemical probe was validated. (Co)polymers have been obtained and the results, especially in terms of kinetics, have been compared to the above systems.

The research reported in this thesis was carried out in Brisbane, Australia and Calgary, Canada. The aim of the research conducted in Brisbane was to prepare a series of copper(I) and ruthenium(II) based complexes incorporating a hemilabile phosphine ligand and to determine whether or not these compounds possessed catalytic activity. The history, uses, properties and recent work incorporating hemilabile phosphine ligands is discussed in detail as well as the application of hemilabile ligands to atom transfer radical polymerization (ATRP) and the usefulness of the 'windscreen wiper' action of these ligands in polymerization. The literature synthesis and characterization of four hemilabile phosphine ligands is reported with modifications. The (2-chlorophenyl)diphenylphosphine ligand was prepared via a Grignard reaction giving a 11% yield. The (2-bromophenyl) diphenylphosphine ligand was prepared by reaction of 2-bromoiodobenzene with Ph2PSiMe3 in the presence of a palladium catalyst (MeCN)2PdCl2 which yielded 50% product. The 1-chloro-2-diphenylphosphinoethane ligand was prepared following the generation of a lithium diphenylphosphide which was added to 1,2-dichloroethane to give a 43% yield of product. The (2-benzoic-acid)diphenylphosphine ligand was prepared by hydrolysis of (2-methyl-ester-phenyl)diphenylphosphine. Following acidification of the methyl ester phosphine with HCl, the desired product was isolated in 88% yield. The synthesis and characterization of a series of copper(I) based complexes incorporating the prepared phosphine ligands involved reaction in CH3CN of the appropriate ligand with copper halides as starting material. Solution state 31P NMR and mass spectrometry were used to study many of these complexes in the solution state, whilst microanalysis, 31P CP MAS NMR and single crystal X-ray diffraction studies were used to study their solid state properties. The complexes of the type bis(2-halophenyl)diphenylphosphine copper halide were found to be three coordinate with non-chelating ligands and to be isostructural with the previously studied bis(2-methylphenyl)diphenylphosphine copper halide complexes. The synthesis and characterization of ruthenium(II) based complexes incorporating hemilabile phosphine ligands involved reaction of the appropriate ligands in MeOH with RuCl3.3H2O or RuCl2(DMSO)4 as the ruthenium source. Modes of characterization included solution state 31P NMR, mass spectrometry, microanalysis and single crystal X-ray diffraction studies. All ruthenium(II) based complexes were found to incorporate the hemilabile ligands in a chelating mode resulting in 6 coordinate structures. The preliminary polymerization testing of MMA in the presence of the copper(I) and ruthenium(II) based complexes has been reported. All complexes successfully polymerized the monomer and the resulting polyMMA showed polydispersity values ranging from moderate (3.1) to very high (6.7). Chapter 7 discusses research conducted over a 6 month period at the University of Calgary, Canada under an International Resident Fellowship award. This work involved the synthesis and characterization of scandium(III) and yttrium(III) based complexes incorporating a chelating amido-imine ligand, as potential olefin polymerization catalysts.

Facile, one-step synthesis of self-assembling, cationic block copolymers of poly(2-N-(dimethylaminoethyl) methacrylate) (pDMAEMA) and PEO-PPO-PEO (Pluronic®) is developed. The copolymers are obtained via free-radical polymerization of DMAEMA initiated by Pluronic-radicals generated by cerium (IV). The copolymers possess surface activity, are polycationic at pH<7.1, and self-assemble into micelle-like aggregates when neutralized. Potential applications of the novel copolymers for DNA transfection in gene therapy are discussed. / Singapore-MIT Alliance (SMA)

Poly(acrylic acid) (PAA) was grafted onto both termini of Pluronic F87 (PEO₆₇-PPO₃₉-PEO₆₇) via atom transfer radical polymerization to produce a novel muco-adhesive block copolymer PAA₈₀-b-F₈₇-b-PAA₈₀. It was observed that PAA₈₀-F₈₇-PAA₈₀ forms stable complexes with weakly basic anti-cancer drug, Doxorubicin. Thermodynamic changes due to the drug binding to the copolymer were assessed at different pH by isothermal titration calorimetry (ITC). The formation of the polymer/drug complexes was studied by turbidimetric titration and dynamic light scattering. Doxorubicin and PAA-b-F87-b-PAA block copolymer are found to interact strongly in aqueous solution via non-covalent interactions over a wide pH range. At pH>4.35, drug binding is due to electrostatic interactions. Hydrogen-bond also plays a role in the stabilization of the PAA₈₀-F₈₇-PAA₈₀/DOX complex. At pH 7.4 (α=0.8), the size and stability of polymer/drug complex depend strongly on the doxorubicin concentration. When CDOX <0.13mM, the PAA₈₀-F₈₇-PAA₈₀ copolymer forms stable inter-chain complexes with DOX (110 ~ 150 nm). When CDOX >0.13mM, as suggested by the light scattering result, the reorganization of the polymer/drug complex is believed to occur. With further addition of DOX (CDOX >0.34mM), sharp increase in the turbidity indicates the formation of large aggregates, followed by phase separation. The onset of a sharp enthalpy increase corresponds to the formation of a stoichiometric complex. / Singapore-MIT Alliance (SMA)

Reversible addition-fragmentation transfer (RAFT) was used as a controlling technique for studying the aqueous heterophase polymerization. The polymerization rates obtained by calorimetric investigation of ab initio emulsion polymerization of styrene revealed the strong influence of the type and combination of the RAFT agent and initiator on the polymerization rate and its profile. The studies in all-glass reactors on the evolution of the characteristic data such as average molecular weight, molecular weight distribution, and average particle size during the polymerization revealed the importance of the peculiarities of the heterophase system such as compartmentalization, swelling, and phase transfer. These results illustrated the important role of the water solubility of the initiator in determining the main loci of polymerization and the crucial role of the hydrophobicity of the RAFT agent for efficient transportation to the polymer particles. For an optimum control during ab-initio batch heterophase polymerization of styrene with RAFT, the RAFT agent must have certain hydrophilicity and the initiator must be water soluble in order to minimize reactions in the monomer phase. An analytical method was developed for the quantitative measurements of the sorption of the RAFT agents to the polymer particles based on the absorption of the visible light by the RAFT agent. Polymer nanoparticles, temperature, and stirring were employed to simulate the conditions of a typical aqueous heterophase polymerization system. The results confirmed the role of the hydrophilicity of the RAFT agent on the effectiveness of the control due to its fast transportation to the polymer particles during the initial period of polymerization after particle nucleation. As the presence of the polymer particles were essential for the transportation of the RAFT agents into the polymer dispersion, it was concluded that in an ab initio emulsion polymerization the transport of the hydrophobic RAFT agent only takes place after the nucleation and formation of the polymer particles. While the polymerization proceeds and the particles grow the rate of the transportation of the RAFT agent increases with conversion until the free monomer phase disappears.<br><br> The degradation of the RAFT agent by addition of KPS initiator revealed unambigueous evidence on the mechanism of entry in heterophase polymerization. These results showed that even extremely hydrophilic primary radicals, such as sulfate ion radical stemming from the KPS initiator, can enter the polymer particles without necessarily having propagated and reached a certain chain length. Moreover, these results recommend the employment of azo-initiators instead of persulfates for the application in seeded heterophase polymerization with RAFT agents.<br><br> The significant slower rate of transportation of the RAFT agent to the polymer particles when its solvent (styrene) was replaced with a more hydrophilic monomer (methyl methacrylate) lead to the conclusion that a complicated cooperative and competitive interplay of solubility parameters and interaction parameter with the particles exist, determining an effective transportation of the organic molecules to the polymer particles through the aqueous phase. The choice of proper solutions of even the most hydrophobic organic molecules can provide the opportunity of their sorption into the polymer particles. Examples to support this idea were given by loading the extremely stiff fluorescent molecule, pentacene, and very hydrophobic dye, Sudan IV, into the polymer particles.<br><br> Finally, the first application of RAFT at room temperature heterophase polymerization is reported. The results show that the RAFT process is effective at ambient temperature; however, the rate of fragmentation is significantly slower. The elevation of the reaction temperature in the presence of the RAFT agent resulted in faster polymerization and higher molar mass, suggesting that the fragmentation rate coefficient and its dependence on the temperature is responsible for the observed retardation. / Um neue Materialien mit außergewöhnlichen Eigenschaften zu erstellen, muss man in der Lage sein, die Struktur der Moleküle zu kontrollieren, aus denen die Materialien bestehen. Für das Maßschneidern solcher neuer Eigenschaften besitzen Polymere ein großes Potenzial: Dies sind sehr lange Moleküle, die aus einer großen Zahl von kleineren Einheiten aufgebaut sind. Proteine und DNS sind Beispiele für natürliche Polymere; Plastik und Gummi sind Beispiele für künstliche Polymere. Letztere werden üblicherweise durch das Zusammenfügen einer Reihe von kleineren Molekülen, den Monomeren, hergestellt. Schon lange versuchen Wissenschaftler, die Anordnung, Anzahl und Art dieser Monomere zu kontrollieren, die sich in der Struktur der Polymermoleküle widerspiegeln. Die gebräuchlichste Methode zur kommerziellen Produktion von Polymeren ist die so genannte freie radikalische Polymerisation. Die Strukturkontrolle durch diese Methode ist jedoch relativ schwierig und wurde maßgeblich erst im letzten Jahrzehnt entwickelt. Trotz der Existenz einiger effektiver Kontrollmethoden ist ihre industrielle Anwendung bislang sehr beschränkt, weil sie nicht für die Emulsionspolymerisation verwendbar sind. Die Emulsionspolymerisation ist die gängigste Technik in der industriellen Produktion von Polymeren. Es handelt sich dabei um ein vergleichsweise umweltfreundliches Verfahren, denn es werden keine organischen Lösungsmittel verwendet. Stattdessen dient Wasser als Lösungsmittel, in dem die Polymere in Form von kleinen, fein verteilten Partikeln vorliegen. In der Natur kommt dieses Prinzip beispielsweise in Pflanzen bei der Bildung von Kautschuk - allgemein als Latex bezeichnet - vor. Schließlich ist die Emulsionspolymerisation einfach durchzuführen: Das Produkt ist in vielen Fällen gebrauchsfertig, und es gibt viele technische Vorteile im Vergleich zu anderen Herstellungsprozessen.<br><br> Doch bevor die Probleme beim Einsatz von Kontrollmethoden in der Emulsionspolymerisation gelöst werden können, müssen erst ihre Ursachen geklärt werden. Dies ist eine unverzichtbare Vorraussetzung zum Übertragen von Forschungsergebnissen auf das tägliche Leben.<br><br> Ziel dieser Arbeit ist die Untersuchung der Probleme, die für die kontrollierte radikalische Polymerisation in Emulsion von Bedeutung sind. Die wichtigste Fragestellung in der Emulsionspolymerisation zielt auf die Löslichkeit der Reaktionskomponenten in den verschiedenen Phasen, wie z.B. in Wasser oder in den Polymerpartikeln. Die Kontrollmethode der Wahl für diese Arbeit ist "Reversibler Additions-Fragmentierungs Transfer" (RAFT). Die RAFT-Methode ist die modernste Kontrollmethode, und sie ist für viele Reaktionsbedingungen und viele Arten von Monomeren anwendbar.