Reported in this thesis are the studies of micellar aggregates of four triblock copolymers and the unimolecular micelles of a triblock copolymer. The micelles were prepared from BCF and ACF copolymers. Here A, B, C, and F denote poly(acrylic acid), poly(tert-butyl acrylate), poly(2-cinnamoyloxylethyl methacrylate), and the liquid crystalline poly(perfluorooctylethyl methacrylate) block, respectively. At room temperature (21 oC) in solvents that were selective for the A or B blocks, three of the four copolymers formed exclusively cylindrical micelles regardless of their block ratios. Cylindrical micelles were formed because their geometries best accommodated the mesogen-ordering requirement of the core-forming F block, as supported by the results from wide angle X-ray scattering and differential scanning calorimetric studies. Mesogen-driven cylinder formation was further supported by the observation of ridges formed by collapsed coronal chains on the surfaces of dried cylinders. We also observed a morphological transformation from other micellar morphologies to cylindrical micelles at 70 oC, which is near the isotropic-to-smectic A phase transition temperature for the F blocks. This inter-conversion between the vesicular and cylindrical micelles of an ACF sample could be reversed repeatly by temperature cycling. These results provided additional evidence for the mesogen-driven micellization hypothesis. Unimolecular micelles were prepared from CDC triblock copolymers, where D and C denote poly(dimethylaminoethyl methacrylate) and poly(2-cinnamoyloxylethyl methacrylate), respectively. In selective solvents for the D block at high dilutions, the D chain formed a loop, and the terminal C blocks of the isolated unimer chain associated together as a globule, thus closing the loop and rendering a cyclic structure. Alternatively, the terminal C blocks formed individual globules, thus yielding a pompom-coil-pompom structure. To lock in these structures, the globules were photo-crosslinked. The D block chain was subsequently enlarged for AFM observation through a quaternization step, which increased the chain’s diameter and introduced cations to the chain. The semi-flexible thickened polymer chains and the globules were observed by AFM, confirming unambiguously the hypothesized architectures of the unimolecular micelles. The AFM images also allowed the quantification of the macrocyclic structures, and a correlation between the direct AFM results and determined from a traditional size exclusion chromatography technique. / Thesis (Ph.D, Chemistry) -- Queen's University, 2011-09-26 12:08:28.263

The goal of this research is to cover a broad set of scientific investigations of elastomeric materials based on polydimethylsiloxane (PDMS) and poly((3,3,3-trifluoroethoxymethyl)methyloxetane) diol. The scope of study covers five areas, well correlated with each other. The first study investigates the near surface morphology of condensation cured PDMS as a function of increasing the amount of siliceous phase. The appearance, disappearance and reappearance of untreated fumed silica nanoparticles at the PDMS near surface and their correlation with the volume fraction of siliceous phase have been studied. This research with PDMS nanocomposites has led to the development of an alternative route for improving mechanical strength of PDMS elastomers, conventionally known to have weak mechanical properties. The second study involves synthesis of a triblock copolymer comprising of four mutually immiscible phases, namely, soft segments comprising of fluorous and silicone domains, a diisocyanate hard segment and a glassy siliceous phase. Structure-property relationship has been established with an investigation of the interesting surface and bulk morphology. The highly improved mechanical strength of these soft materials is noteworthy. The dominance of silicone soft block at the triblock near surface has led to the third study which investigates their potential non-adhesive or abhesive characteristic in both a laboratory scale and in a marine environment. The peak removal stress and the removal energy associated with the detachment of a rigid object from the surface of these triblock copolymers have been measured. Results obtained from laboratory scale experiments have been verified by static immersion tests performed in the marine environment, involving the removal of adhered soft and hard fouling organisms. Gaining insights on the characteristics of an easy release surface, namely low surface energy and a low near surface modulus, a new way for controlling the near surface composition for elastomeric coatings have been developed. This technique involves an elastomer end-capped with a siliceous crosslinking agent and a tough, linear polyurethane. The basic concept behind the hybrid compositions is to develop a coating suitable for foul release applications, having a low energy surface, low surface modulus but good bulk mechanical strength. Henceforth, the fourth study deals with synthesis and characterization of the hybrid polymers over a wide range of composition and investigates their foul release characteristic in laborartory scale experiments. In our final study, attempts have been made in generating a silicone coating with antimicrobial property. A quaternary alkylammonium in different weight percents have been incorporated into a conventional, condensation cured polydimethylsiloxane (PDMS) elastomer. Antimicrobial assay has been performed on these modified silicone coatings to assess their biocidal activity against strains of Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. Surface accessibility of quaternary charges has been quantified by measuring the streaming potential of a modified coating. An effort has been made in improving the mechanical strength of the weak PDMS elastomers by adding treated fumed silica nanoparticles as reinforcements. The effect of adding fillers on the mechanical property (tensile), surface concentration of quaternary charge and on the biocidal activity of a representative sample has been investigated.

Sixteen millions of people are diabetics in the United States. Finding an oral way to deliver the insulin they need would improve the quality of their life. For this purpose biodegradable and biocompatible nanovesicles encapsulating some insulin have been synthesized. Those nanovesicles are made by self-assembly of a triblock copolymer poly(ethylene glycol)-bpoly( lactic acid)-b-poly(glutamic acid) (PEG-b-PLA-b-PGlu). The triblock copolymer has been prepared in several steps by multi-step anionic ringopening polymerization. The first step consisted in the preparation of the diblock copolymer PEG-b-PLA. This diblock copolymer was synthesized by ring opening of racemic lactide, using a zinc alkoxide as an initiator. The second step was the synthesis of the poly(glutamic acid). The polybenzyl(glutamic acid) was obtained by ring opening polymerization of the N-Carboxyanhydride of the corresponding amino acid. Finally, the benzyl group was deprotected via protonolysis, to generate the homopolymer. This triblock was successfully obtained by coupling a diblock copolymer PEG-bxv PLA and a homopolymer poly(glutamic acid). In the presence of an aqueous solution of insulin where the pH is between 7 and 9, the triblock copolymer self-assembles in nanovesicles containing a part of the free insulin. In the intestine, the vesicles are highly solvated due to the deprotonnated poly(glutamic acid) hair which are expected to be located on the outside. Moreover, to resist from the gastric acidity, the nanovesicles are protected with gastro resistant polymer, Eudragit, which stay solid at acidic pH but get dissolved in the intestine (where the pH is slightly basic), releasing the vesicles. All the polymers have been characterized using 1H NMR and GPC. The percentage of encapsulation of insulin has been measured by HPLC some in-vivo experiments have been done on Sprague-Dawley rats.

Microemulsions have important applications in various industries, including enhanced oil recovery, reactions, separations, drug delivery, cosmetics and foods. We investigated two different kinds of water-in-oil microemulsion systems, AOT (bis(2-ethylhexyl) sulfosuccinate) microemulsions with various counterions and perfluorocarbon-based microemulsion gels with triblock copolymers. In the AOT systems, we investigated the viscosity and interdroplet interactions in Ca(AOT)2, Mg(AOT)2 and KAOT microemulsions, and compared our results with the commonly-studied NaAOT/water/decane system. We attribute the differences in behavior to different hydration characteristics of the counterions, and we believe that the results are consistent with a previously proposed charge fluctuation model. Perfluorocarbons (PFCs) are of interest in a variety of biomedical applications as oxygen carriers. We have used triblock copolymer Pluronic® F127 to modify the rheology of PFC-based microemulsions, we have been able to form thermoreversible PFOB (perfluorooctyl bromide)-based gels, and have investigated the phase stability, rheology, microstructure, interactions, and gelation mechanism using scattering, rheometry, and microscopy. Finally, we attempted to use these data to understand the relationship between rheology and structure in soft attractive colloids.

Crosslinkable and pH-sensitive amphiphilic block copolymers are promising candidates to establish pH-stable and permeable vesicles for synthetic biology. Here, we report the fabrication of crosslinked and pH-stable polymersomes as swellable vesicles for the pH-dependent loading and release of small dye molecules. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

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

Abstract: ABC triblock copolymers self-organize into a wide variety of supramolecular structures in the bulk. However, their associative behavior in selective solvents has scarcely been studied. Within the search for new stimuli-responsive supramolecular architectures, our attention focused on a pH-responsive polystyrene-b-poly(2-vinylpyridine)-b-poly(ethylene oxide) (PS-b-P2VP-b-PEO) triblock copolymer. In addition to the synthesis of monodisperse spherical core-shell-corona (CSC) micelles, the reversibility and the cooperativity of the response to pH variations were studied, morphological transitions were induced and multi-responsive micellar gels were prepared. The micellization mechanism, the structure, the responsiveness and the internal organization of these new nanomaterials were investigated using a combination of transmission electronic microscopy, atomic force microscopy, light scattering, small-angle neutron and X-ray scattering, nuclear magnetic resonance and rheology. Finally, efforts were geared towards potential applications. The ability of PS-b-P2VP-b-PEO CSC micelles to encapsulate and release hydrophobic species was probed and gold nanoparticles were successfully synthesized within the P2VP layer of spherical and cylindrical micelles, which acted as nanoreactors./Résumé : Les copolymères triséquencés ABC sauto-organisent et forment une large gamme de structures supramoléculaires en phase solide. Cependant, peu détudes portent sur leur comportement associatif induit par des solvants sélectifs. Dans le cadre de la recherche de nouvelles architectures supramoléculaires sensibles aux stimuli externes, nous avons entrepris létude dun copolymère triséquencé sensible au pH : polystyrène-b-poly(2-vinylpyridine)-b-poly(oxyde déthylène). Outre la synthèse de micelles sphériques de type CSC, le caractère réversible et coopératif de la réponse au pH a été étudié, ainsi que linduction de transitions morphologiques et la préparation de gels micellaires sensibles à la température et au pH. Le mécanisme de micellisation, les paramètres structuraux, la sensibilité aux stimuli ainsi que lorganisation interne de ces nouveaux nanomatériaux ont été étudiés par une combinaison de microscopies électronique à transmission et à force atomique, diffusion lumineuse, diffusion de neutrons et rayons X aux petits angles, résonance magnétique nucléaire et rhéologie. Enfin, des applications ont été envisagées : la capacité des micelles CSC à encapsuler et libérer des composés hydrophobes a été testée et des nanoparticules dor ont été synthétisées avec succès au sein de ces nanoréacteurs, cest-à-dire dans la couche de P2VP des micelles sphériques et cylindriques.

New ABC triblock copolymers were synthesized by controlled free-radical polymerization via Reversible Addition-Fragmentation chain Transfer (RAFT). Compared to amphiphilic diblock copolymers, the prepared materials formed more complex self-assembled structures in water due to three different functional units. Two strategies were followed: The first approach relied on double-thermoresponsive triblock copolymers exhibiting Lower Critical Solution Temperature (LCST) behavior in water. While the first phase transition triggers the self-assembly of triblock copolymers upon heating, the second one allows to modify the self-assembled state. The stepwise self-assembly was followed by turbidimetry, dynamic light scattering (DLS) and 1H NMR spectroscopy as these methods reflect the behavior on the macroscopic, mesoscopic and molecular scale. Although the first phase transition could be easily monitored due to the onset of self-assembly, it was difficult to identify the second phase transition unambiguously as the changes are either marginal or coincide with the slow response of the self-assembled system to relatively fast changes of temperature. The second approach towards advanced polymeric micelles exploited the thermodynamic incompatibility of “triphilic” block copolymers – namely polymers bearing a hydrophilic, a lipophilic and a fluorophilic block – as the driving force for self-assembly in water. The self-assembly of these polymers in water produced polymeric micelles comprising a hydrophilic corona and a microphase-separated micellar core with lipophilic and fluorophilic domains – so called multi-compartment micelles. The association of triblock copolymers in water was studied by 1H NMR spectroscopy, DLS and cryogenic transmission electron microscopy (cryo-TEM). Direct imaging of the polymeric micelles in solution by cryo-TEM revealed different morphologies depending on the block sequence and the preparation conditions. While polymers with the sequence hydrophilic-lipophilic-fluorophilic built core-shell-corona micelles with the core being the fluorinated compartment, block copolymers with the hydrophilic block in the middle formed spherical micelles where single or multiple fluorinated domains “float” as disks on the surface of the lipophilic core. Increasing the temperature during micelle preparation or annealing of the aqueous solutions after preparation at higher temperatures induced occasionally a change of the micelle morphology or the particle size distribution. By RAFT polymerization not only the desired polymeric architectures could be realized, but the technique provided in addition a precious tool for molar mass characterization. The thiocarbonylthio moieties, which are present at the chain ends of polymers prepared by RAFT, absorb light in the UV and visible range and were employed for end-group analysis by UV-vis spectroscopy. A variety of dithiobenzoate and trithiocarbonate RAFT agents with differently substituted initiating R groups were synthesized. The investigation of their absorption characteristics showed that the intensity of the absorptions depends sensitively on the substitution pattern next to the thiocarbonylthio moiety and on the solvent polarity. According to these results, the conditions for a reliable and convenient end-group analysis by UV-vis spectroscopy were optimized. As end-group analysis by UV-vis spectroscopy is insensitive to the potential association of polymers in solution, it was advantageously exploited for the molar mass characterization of the prepared amphiphilic block copolymers. / Die Arbeit widmet sich der Synthese von neuen amphiphilen ternären "ABC" Block-Copolymeren und der Untersuchung ihrer Selbstorganisation zu mizellaren Überstrukturen in wässriger Lösung. Die Block-Copolymere wurden durch kontrollierte radikalische Polymerisation mittels des sogenannten „RAFT“ Prozesses (radical addition fragmentation chain transfer) hergestellt. Neben der Realisierung der gewünschten Polymerarchitekturen erlaubte es die Methode, die Molmassen der Polymere durch Endgruppenanalyse zu bestimmen. Die Kettenenden der Polymere tragen infolge des Polymerisationsmechanismus’ definierte Funktionalitäten, welche UV- und sichtbares Licht absorbieren und somit durch UV-vis-Spektroskopie quantifizierbar sind. Das Absorptionsverhalten der Endgruppen wurde untersucht und die UV-vis-Endgruppenanalyse optimiert. Es zeigte sich, dass die Vorteile der Methode ihre generelle Anwendbarkeit und ihre Unempfindlichkeit gegenüber der Assoziation von Polymeren in Lösung sind. Aufgrund ihrer drei unterschiedlichen Blöcke bilden die synthetisierten ABC Triblockcopolymere komplexere selbstorganisierte Strukturen als die bisher üblichen Diblockcopolymere. Die Triebkraft für ihre Selbstorganisation in wässriger Lösung ist im wesentlichen der hydrophobe Effekt. Es wurden zwei unterschiedliche Ansätze verfolgt: Zum einen wurden doppelt-schaltbare Triblockcopolymere hergestellt, von denen ein Block permanent wasserlöslich ist, während die anderen Blöcke jeweils eine untere Entmischungstemperatur in wässriger Lösung aufweisen. Diese Blöcke „schalten“ beim Erwärmen von hydrophil auf hydrophob. Oberhalb des ersten Phasenübergangs - bei der niedrigeren Entmischungstemperatur - assoziieren die Makromoleküle und bilden Polymermizellen im Nanometerbereich. Beim weiteren Erwärmen „schaltet“ auch der zweite Block und modifiziert den selbstorganisierten Zustand, während der permanent wasserlösliche Block für die Stabilisierung der Aggregate sorgt. Die Assoziation der Block-Copolymere ist nach Abkühlen der wässrigen Lösung vollständig reversibel. Die stufenweise Selbstorganisation wurde mit Hilfe von Turbidimetrie, Dynamischer Lichtstreuung (DLS) und 1H-NMR-Spektroskopie untersucht, da diese Methoden das Verhalten auf der makroskopischen, mesoskopischen und molekularen Skala widerspiegeln. Obwohl der einsetzende Selbstorganisationsprozess problemlos zu detektieren war, konnten die Veränderungen infolge des zweiten Phasenübergang nicht immer eindeutig identifiziert werden, da sie zum Teil mit der langsamen Reaktion des Systems auf relativ schnelle Temperaturänderungen zusammenfielen. Außerdem hängt die Aggregatbildung nicht nur sensibel von der detaillierten Polymerarchitektur ab, sondern unterliegt auch teilweise einer kinetischen Kontrolle. Der zweite Ansatz zu komplexeren Polymermizellen basierte auf der Inkompatibilität „triphiler“ Blockcopolymere als Triebkraft für die Selbstorganisation. Das heißt, die Block-Copolymere bestehen aus einem hydrophilen, einen lipophilen und einen fluorophilen (Fluorkohlenwasserstoff-liebenden) Teil, die jeweils miteinander unverträglich sind. Die Polymere assoziierten in Wasser zu Polymermizellen mit einer hydrophilen Korona und einem unterstrukturierten Mizellkern mit separaten Kohlenwasserstoff- und Fluorkohlenwasserstoff-Domänen – sogenannten Multi-Kompartiment-Mizellen. Die Assoziation der Triblock-Copolymere wurde mit 1H-NMR-Spektroskopie, DLS und cryogener Transmissionselektronenmikroskopie (cryo-TEM) untersucht. Die unmittelbare Abbildung der Polymermizellen in Lösung mittels cryo-TEM enthüllte unterschiedliche Morphologien in Abhängigkeit von der Blocksequenz und den Präparationsbedingungen. Während Polymere mit der Blocksequenz hydrophil-lipophil-fluorophil Kern-Schale-Korona-Mizellen mit der Fluor-Domäne als Kern bildeten, wurde eine neue, unerwartete Mizellmorphologie für die Polymere mit dem hydrophilen Block in der Mitte gefunden: Einzelne oder mehrere Fluordomänen “schwimmen” als Scheiben auf dem lipophilen Kern. Die beobachteten Morphologien sind weitgehend stabil, unterliegen aber ebenfalls - zumindest teilweise - einer kinetischen Kontrolle. So führten erhöhte Temperaturen während der Mizellpräparation gelegentlich zu einer Veränderung der Mizellmorphologie oder Partikelgröße.

ABC type amphiphilic triblock copolymers, polyethylene-b-poly(ethylene oxide)-b-poly (£`-caprolactone) (PE-b-PEO-b-PCL), were synthesized through ring-opening polymerization. We have successfully synthesized hierarchical mesoporous silicas using a simple evaporation-induced self-assembly (EISA) strategy. Two blocks of hydrophobic segment (PE and PCL) in the triblock copolymer (PE-b-PEO-b-PCL) involved in two-type mesepores after calcinations. We recognized the PE segment attributed to face centered cubic (f. c. c.) morphology (spherical pore) and the PCL segment attributed to tetragonal cylinder structure (cylinder pore) by small angle X-ray scattering (SAXS), transmission electron microscopy (TEM) and specific surface area & pore size distribution analyzer (BET), respectively. We also investigated the effect on pore size and morphology with changing the molecular weight of PCL and the ratios of TEOS/template/HCl. We also synthesized the mesoporous phenolic resin by triblock copolymer poly(ethylene oxide)-b-poly(£`-caprolactone)-b-poly(L-lactide) (PEO-b-PCL-b-PLLA). After curing and calcinations, we also explored the morphology and pore size distribution of mesoporous phenolic by SAXS, TEM, BET. Because of the sequence of hydrophobic segment PCL and PLLA lay in the same side, so we could only observe hexagonal cylinder structure and one pore size.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / O objetivo deste trabalho foi investigar misturas de sistemas de copolÃmeros triblocos do tipo E62P39E62 (comercialmente chamado de F87) e E137S18E137 (sintetizado por polimerizaÃÃo aniÃnica e denominado de S18) como novos veÃculos para solubilizaÃÃo e liberaÃÃo controlada de fÃrmacos. As caracterÃsticas desejÃveis de gelatinizaÃÃo das soluÃÃes do copolÃmero E62P39E62 combinadas com as capacidades de solubilizaÃÃo das soluÃÃes do copolÃmero E137S18E137 foram estudadas utilizando o mÃtodo de inversÃo de tubo e por reologia oscilatÃria. A estrutura dos gÃis foi obtida por espalhamento de raios-X a baixos Ãngulos (SAXS) e por microscopia de luz polarizada (PLM). O raio hidrodinÃmico (rh) das micelas foi obtido por espalhamento de luz dinÃmico (DLS), e a capacidade de solubilizaÃÃo (scp) dos copolÃmeros separados e para as misturas dos dois na faixa 50/50 a 90/10 %m/m de E62P39E62/E137S18E137, foi avaliada por espectroscopia de ultravioleta-visÃvel (UV-Vis). Os limites gel/fluido dos copolÃmeros isolados e suas misturas foram determinados pelo mÃtodo de inversÃo de tubo e confirmado por reometria. Os resultados de SAXS e PLM para a mistura 1 (50/50 % m/m E137S18E137/E62P39E62 e para E137S18E137 e E62P39E62 isolados), indicaram estrutura cÃbica de corpo centrado (ccc), conforme indicado por reologia. DLS indicou a formaÃÃo de micelas determinadas pelo copolÃmero E62P39E62. A scp dos copolÃmeros e misturas revelou resultados promissores para aplicaÃÃo de misturas binÃrias de copolÃmeros como sistemas de liberaÃÃo de fÃrmacos envolvendo gelatinizaÃÃo in situ. / The aim of this work was to investigate mixed systems of triblock copolymer type E62P39E62 (commercially denoted F87) and E137S18E137 (prepared by oxyanionic polymerization) as novel vehicles for solubilisation and controlled delivery of aromatics drugs The desirable gelation characteristics of solutions of the EmPnEm copolymers with the greater solubilising capacities of solutions of the EmSnEm were investigatedo using an inverted tube test method and by oscillatory rheometry. The structure of the gels was obtained by small angle X-ray scattering (SAXS) and polarized-light microscopy (PLM).The hydrodynamic radius (rh) of the micelle was obtained by dynamic light scattering (DLS). The solubilisation capacity (scp) for the separate copolymers and for mixtures of the two in the range 50/50 to 90/10 wt % E137S18E137/E62P39E62was evaluated by UV-Vis. The fluid/gel boundaries for the copolymers alone and its mixtures were determined by the tube inversion method and confirmed by rheometry. SAXS and PLM for mixture 1 (50/50 wt % E137S18E137/E62P39E62 and for E137S18E137 and E62P39E62 alone) all have shown similar body-centred cubic (bcc) structures with similar lattice dimensions as confirmed by rheology. DLS indicated micelle formation determined by E62P39E62 copolymer. The scp measured for the separate copolymers and its mixtures revealed promise results for application of binary mixtures of copolymer as systems for drug release involving in situ gelation.