No description available.

Ion-containing segmented polyurethanes exhibit unique morphology and physical properties due to synergistic interactions of electrostatic, hydrogen bonding, and hydrophobic interactions. A fundamental investigation on a series of well-defined ion-containing polyurethanes elucidated the influence of charge placement, charge density, and soft segment structure on physical properties, hydrogen bonding, and morphologies. An unprecedented comparison of poly(ethylene oxide)(PEO)-based sulfonated polyurethanes containing sulfonate anions either in the soft segments or hard segments revealed that sulfonate charge placement dramatically influenced microphase separation and physical properties of segmented polyurethanes, due to altered hydrogen bonding and thermodynamic immiscibility between soft and hard segments. Moreover, studies on sulfonated polyurethanes with identical sulfonated hard segments but different soft segment structures indicated that soft segment structure tailored sulfonated polyurethanes for a wide range of mechanical properties. Sulfonated polyurethanes incorporated with ammonium-functionalized multi-walled carbon nanotubes (MWCNTs) generated novel polyurethane nanocomposites with significantly enhanced mechanical performance. Modification of MWCNTs followed a dendritic strategy, which doubled the functionality by incorporating two ammonium cations per acid site. Complementary characterization demonstrated successful covalent functionalization and formation of surface-bound ammonium salts. Upon comparison with pristine MWCNTs, ammonium-functionalized MWCNTs exhibited significantly enhanced dispersibility in both DMF and sulfonated polyurethane matrices due to good solvation of ammonium cations and intermolecular ionic interactions between anionic polyurethanes and cationic MWCNTs. Segmented polyurethanes containing sulfonated PEO-based soft segments and nonionic hard segments were incorporated with various contents of room temperature ionic liquid, 1-ethyl-3-methylimidazolium ethylsulfate (EMIm ES), to investigate the influence of ionic liquid on physical properties, morphologies, and ionic conductivity. Results indicated that EMIm ES preferentially located in the sulfonated PEO soft phase, leading to significantly enhanced ionic conductivity and well-maintained mechanical properties. These properties are highly desirable for electromechanical transducer applications. Electromechanical actuators fabricated with sulfonated polyurethane/IL composite membranes exhibited effective response under a low applied voltage (4 V). However, in the case of an imidazolium-containing segmented polyurethane with imidazolium ionic hard segments and hydrophobic poly(tetramethylene oxide) (PTMO) soft segments, EMIm ES selectively located into the imidazolium ionic hard domains, as evidenced with a constant PTMO soft segment glass transition temperature (Tg) and systematically reduced imidazolium hard segment Tg. Dielectric relaxation spectroscopy demonstrated that ionic conductivity of imidazolium-containing segmented polyurethanes increased by five orders of magnitude upon incorporation of 30 wt% EMIm ES. Imidazolium-containing sulfonated pentablock copolymers were also investigated to elucidate the influence of imidazolium counter cation structures on solution rheology, morphology, and thermal and mechanical properties. Combination of living anionic polymerization and post functionalization strategies provided well-defined sulfonated pentablock copolymers containing structured imidazolium cations in sulfonated polystyrene middle block. Varying alkyl substitute length on imidazolium cations tailored physical properties and morphologies of sulfonated pentablock copolymers. Results indicated that long alkyl substitutes (octyl and dodecyl) on imidazolium cations significantly influenced solution rheological behavior, morphology, and water uptake properties of sulfonated pentablock copolymers due to the altered characteristic of imidazolium cations. Imidazolium-containing sulfonated pentablock copolymers exhibited systematically tailored mechanical properties due to the plasticizing effect of alkyl substitutes. In addition, incorporation of ionic liquids into sulfonated pentablock copolymers further tailored their mechanical properties and ionic conductivity, which made these materials suitable for electromechanical transducer applications. All sulfonated pentablock copolymers were successfully fabricated into actuator devices, which exhibited effective actuation under a low applied voltage (4 V). / Ph. D.

Silicon and silicon-based materials have been investigated for the fabrication of electronic, optoelectronic, solar, and structural/mechanical devices. To enable the continuous use of silicon-based materials for next generation device applications, new and inexpensive ways of fabricating features of silicon, and silica-based materials are needed. This dissertation investigates: 1) novel techniques for the fabrication of silica and silicon nanofeatures with potential application in the electronics and optoelectronics industry; 2) new designs of photomodifiable material systems (resists) for maskless patterning of silica filled composites for structural/mechanical applications. Sub-micron and nano-scaled features were fabricated onto silicon and silicon oxide substrates using a technique combining block copolymers and laser interference ablation. The sacrificial block copolymers are loaded with metallic salt precursors and patterned with a UV laser to generate device-oriented nanofeatures. New photopolymerizable material systems (negative tone resists) were developed based on curcumin photosensitizer and an epoxy-acrylate, vinylether, and vinylether-acrylate silica¬-loaded material systems. The cationic and radical mechanisms employed by the monomeric systems under a high vapor pressure mercury lamp source were investigated with several materials characterization techniques.

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The combination of natural and synthetic polymers allow for the synthesis of advanced hybrid copolymers. These hybrid copolymers have applications in biomedical areas, one such area being in drug delivery systems (DDS). In this study, a modular approach was used to prepare amphiphilic block copolymers with the ability to self-assemble into three dimensional structures. Reversible addition-fragmentation chain transfer (RAFT) was the synthetic tool used to mediate the polymerization of N-vinylpyrrolidone. RAFT is a versatile method to prepare polymers with control over molecular weight and dispersity. A xanthate chain transfer agent (CTA) was used to obtain the hydrophilic poly(N-vinylpyrrolidone) (PVP) block. An aldehyde functionality could be introduced due to the lability of the xanthate moiety, the procedure of which was effectively optimized to produce quantitative conversion. A dixanthate CTA was synthesized to produce a PVP chain which after the modification reaction, resulted in a α,ω-telechelic polymer. A polypeptide was synthesized via the ring-opening polymerization of Ncarboxyanhydrides (ROP NCA). The living and controllable ROP of NCAs is a method which results in polypeptides, but without a well-defined amino acid order. Poly(γ- benzyl-L-glutamate) (PBLG) was synthesized with a narrow dispersity (Đ = 1.10 – 1.15) using conditions that promote the retention of a terminal primary amine. A protected cysteine functionality was introduced via the terminal amine PBLG chain-end, using peptide synthesis techniques. This resulted in the conjugation of the aldehyde functional PVP and the cysteine terminal PBLG using a covalent, non-reducible thiazolidine linkage. The deprotection of the cysteine, more specifically the deprotection of the thiol was a non-trivial procedure. The thiol protecting acetamidomethyl (Acm) group could not be cleaved using traditional methods, but instead a modified procedure was developed to effectively remove the Acm group while inhibiting hydrolysis of the benzyl esters. It was determined that the conjugation reaction could effectively proceed in N,Ndimethylformamide (DMF) at a slightly elevated temperature and so continued to prepare the amphiphilic hybrid block copolymers, PVP-b-PBLG. A structurally different PBLG chain, namely PBLG-b-Cys was conjugated to the ω-aldehyde PVP and the conjugation efficiency was compared to our PBLG-Cys block. In the case of PBLG-b- Cys the in situ deprotection and conjugation as well as a two-step deprotection and conjugation reaction with PVP resulted in very low conjugation efficiency. The cysteine end-functional PBLG resulted in near quantitative conjugation with PVP. The critical micelle concentration (CMC) for PVP90-b-PBLG54 was determined to be 6 μg/mL, using fluorescence spectroscopy. Particle sizes were determined with TEM and DLS and found to range from 25 nm to 120 nm depending on the polymer block lengths as well as hydrophobic/hydrophilic block length ratios. Furthermore, when the micelles were subjected to an increased acidic environment, the labile benzyl ester bonds were hydrolyzed. This was observed with TEM where the particle sizes increased 10-fold to form vesicular structures. Hydrolysis was further confirmed with ATR-FTIR and 1H-NMR spectroscopy. Cytotoxicity tests confirmed that the copolymer micelles had good cell compatibility at high concentrations such as 0.9 mg/mL. Investigation into drug loading using a pyrene probe confirmed the viability of using PVP-b-PBLG as a responsive DDS. / AFRIKAANSE OPSOMMING: Die kombinasie van natuurlike en sintetiese polimere maak dit moontlik vir die sintese van gevorderde hibried kopolimere. Hierdie kopolimere het aanwending in biomediese gebiede, een so 'n gebied is in medisinale vervoer sisteme (MVS). 'n Modulêre benadering is in hierdie studie gebruik om amfifiliese blok kopolimere te berei. Omkeerbare addisie-fragmentasie kettingoordrag (OAFO) is gebruik as die sintetiese tegniek vir die polimerisasie van N-vinielpirolidoon (NVP). OAFO is 'n veelsydige metode om polimere te berei met beheer oor molekulêre gewig en dispersiteit (Đ). 'n Xantaat kettingoordrag agent (KOA) is gebruik om die hidrofiliese poli(N-vinielpirolidoon) (PVP) blok te sintetiseer. ‘n Aldehied endgroep was deur die terminale xantaat funksionaliteit berei, ‘n proses wat geoptimiseer is tot kwantitatiewe omsetting. 'n Di-xantaat KOA is gesintetiseer om, na modifikasie, 'n α, ω-telecheliese polimeer te produseer. Die polipeptied was gesintetiseer deur middel van ’n ringopening polimerisasie van Nkarboksianhidriede (ROP NKA). Die lewende en beheerbare ROP van NKAe is 'n metode wat lei tot polipeptiede sonder ’n gedefinieerde aminosuur volgorde. Poli(γ- benzyl-L-glutamaat) met 'n lae dispersiteit (Đ = 1.10 – 1.15), is gesintetiseer deur gebruik te maak van kondisies wat die behoud van 'n terminale primêre amien bevorder. 'n Beskermde sistien-funksionaliteit is ingebou via die terminale amien met behulp van peptiedsintese tegnieke. Die tiol beskerming van die asetamidometiel (Asm) groep kon nie gekleef word deur gebruik te maak van tradisionele metodes nie, maar ‘n nuwe proses is ontwikkel om die Asm groep te kleef sowel as om die hidrolise van die bensiel esters te inhibeer. Die koppelings reaksie het effektief verloop in DMF by 'n effens verhoogde temperatuur en sodoende is die amfifiliese hibried blok-kopolimere, PVP-b-PBLG berei. Twee verskillende PBLG kettings is gekoppel aan die ω-aldehied PVP en die koppeling doeltreffendheid is vergelyk. Daar is bevind dat net die sistien end-funksionele PBLG tot kwantitatiewe konjugasie kon lei. Die kritiese misel konsentrasie is bepaal vir PVP90-b-PBLG54 as 6 μg/mL met behulp van fluoressensie spektroskopie. Die deeltjie-groottes is bepaal met TEM en DLS en wissel van 25 nm tot 120 nm, afhangende van die polimeer bloklengtes sowel as hidrofobiese / hidrofiliese blok lengte verhoudings. Die miselle is blootgestel aan 'n verhoogde suur omgewing, wat tot die hidrolise van die bensiel ester groepe gelei het. TEM het getoon dat die deeltjie-groottes met 10-voud vergroot het tot vesikulêre strukture. Hidrolise is verder bevestig met ATR-FTIR en 1H-KMR spektroskopie. Sitotoksiese toetse het bevestig dat die miselle geen of min toksisiteit toon teenoor eukariotiese selle nie, selfs teen 'n hoë konsentrasies soos 0.9 mg/ml. Die medisinale behoud vermoë is met behulp van pireen bevestig en dus ook die potensiaal van PVP-b-PBLG as ‘n moontlike MVS.

Les travaux décrits dans ce manuscrit ont trait à l’élaboration de supports organiques fonctionnels à base de polyisoprène pour la catalyse de polymérisation de l’éthylène par les métallocène et post-métallocène. Une série de polyisoprènes ω-OH et de copolymères à blocs de type polyisoprène-b-poly(méthacrylate de méthyle) et polyisoprène-b-poly(oxyde d’éthylène) de masse molaire variable a été réalisée par polymérisation anionique vivante. L’auto-assemblage dans l’heptane de ces (co)polymères conduit à la formation d’agrégats micellaires stables qui permettent l’immobilisation des systèmes catalytiques via des interactions créées entre le bloc polaire du support et l’activateur aluminique, le plus souvent le méthylaluminoxane. La polymérisation de l’éthylène en présence de ces supports organiques conduit, sans diminution d’activité catalytique, à la formation de particules de polyéthylène de taille micrométrique. Selon la même méthodologie, des polyisoprènes portant à leur extrémité une fonction borate ont été synthétisés et avantageusement utilisés comme supports activateurs de métallocènes pré-alkylés. Dans ce cas, des particules de polyéthylène de taille millimétrique ont pu être obtenues. / The work described in this manuscript relates the development of organic functional supports based on polyisoprene for the catalysis of ethylene polymerization by metallocenes and post-metallocenes. Polyisoprenes ω-OH and block copolymers [polyisoprene-b-poly(methyl methacrylate) and polyisoprene-b-poly(ethylene oxide)] with different molecular weights were synthesized by living anionic polymerization. Self-assembly in heptane of (co)polymers leads to the formation of stable micellar aggregates allowing the immobilization of catalytic systems created thanks to interactions between the polar block of the support and the aluminic activator, the most often methylaluminoxane. The ethylene polymerization in the presence of organic support drives, without loss of catalytic activity, to the formation of polyethylene particles of micrometer size. Using the same methodology, polyisoprenes bearing at their ends a borate function have been synthesized and advantageously used as supports activators of pre-alkylated metallocenes. In this case, polyethylene particles with a millimeter size have been obtained.

Les micelles complexes de polyions, ou « micelles PIC », formées par interaction électrostatique entre un copolymère à blocs double hydrophile neutre-ionique (DHBC) et un homopolyélectrolyte de charge opposée au DHBC possèdent des propriétés particulièrement intéressantes : solubilité des polyélectrolytes dans l'eau, stabilité des micelles, contrôle de l'association/dissociation micellaire par divers stimuli (pH, force ionique, irradiation lumineuse…). Dans cette thèse, les propriétés physico-chimiques des micelles PIC de type DHBC neutre-cationique/homopolymère anionique et DHBC neutre-anionique/homopolyélectrolyte cationique ont été étudiées en solution aqueuse en vue de leur utilisation comme agent structurant des matériaux siliciques organisés à l'échelle nanométrique. La gamme de pH de formation des micelles PIC, la concentration micellaire critique et le nombre d'agrégation des micelles ont été déterminés pour chacun des systèmes étudiés. Nous avons montré que la formation des micelles suit un mécanisme coopératif qui dépend de la taille de l'homopolymère. Par ailleurs, nous avons proposé une voie originale de formation des micelles PIC photoinduite, basée sur une modification du pH suite à l'irradiation d'une molécule photochrome. Les études concernant l'utilisation des micelles PIC comme agent structurant des matériaux nous ont permis de montrer que la morphologie (nanoparticulaire, massif) et la structure des matériaux (lamellaire, vermiculaire) peuvent être contrôlés par divers paramètres, tels que la concentration en masse du système DHBC/homopolyélectrolyte/précurseur de silice, la teneur en précurseur de silice et le rapport entre les fonctions cationique et anionique des polyélectrolytes. Le lavage des matériaux sous des conditions douces (à l'eau) permet de récupérer l'agent structurant. / Polyion complex micelles, or "PIC micelles", formed by electrostatic interaction between a neutral-ionic double hydrophilic block copolymer (DHBC) and an oppositely charged homopolyelectrolyte possess interesting properties: solubility of the polyelectrolytes in water, stability of micelles, control of the micellar association / dissociation by various stimuli (pH, ionic strength, light irradiation ...). In this thesis, the physico-chemical properties of PIC micelles of neutral-cationic DHBC/ anionic homopolymer and neutral-anionic DHBC/cationic homopolymer were studied in aqueous solution for use as structuring agents of silica-based organized nanomaterials. The pH range of PIC micelle formation, the critical micelle concentration and aggregation number of micelles were determined for each studied system. We have shown that the formation of micelles follows a cooperative mechanism which depends on the size of the homopolymer. Furthermore, we proposed an original way of photoinduced PIC micelle formation, based on a pH change after irradiation of a photochromic molecule. The studies on the PIC micelles as structuring agents of materials have shown that the morphology (nanoparticular, bulk) and the material structure (lamellar, vermicular) can be controlled by various parameters, such as the mass concentration of the DHBC / homopolyelectrolyte / silica precursor system, the content of the silica precursor and the ratio between the functions of the cationic and anionic polyelectrolytes. Finally, the template was removed by washing the hybrid materials under soft conditions in water.

This thesis deals with (i) complex nanoaggregates of cationic perfluorinated surfactant N-(1,1,2,2- tetrahydroperfluorodecyl)pyridinium chloride and of double hydrophilic block polyanions poly(ethylene oxide)-b-poly(methacrylate) and poly(ethylene oxide)-b-poly((2-sulfamate-3- carboxylate)isoprene), and with (ii) mixed micelles of amphiphilic copolymer poly(ethylene oxide)- b-poly(e-caprolactone) and nonionic perfluorinated fluorosurfactant Zonyl FSN-100. The study was aimed at the characterization of the association behavior of the block copolymer-fluorosurfactant systems in aqueous solutions depending on the amount of the added surfactant, pH of the solvent and the structure of the copolymers.

Ce est consacré à l’élaboration et à l’étude de mélanges de type polymères/maltènes (MP) et polymères/asphaltes (AMP). Les polymères sont des copolymères à blocs de styrène et de butadiène (SBS) présentant une architecture ramifiée en étoile à quatre branches. Ils ont été partiellement hydrogénés en SBEBS grâce à l’utilisation d’un catalyseur type Ziegler-Natta. Dans les conditions expérimentales utilisées, les analyses physico-chimiques des SBEBS ont clairement montré que l’hydrogénation a été réalisée sans dégradation ni réticulation des chaînes macromoléculaires. Les mélanges, fabriqués sous agitation à l’état fondu, ont ensuite été caractérisés par rhéologie et microscopie de fluorescence. Les résultats obtenus permettent d’établir que : - selon la teneur en copolymère, les AMP présentent soit une morphologie de type émulsion soit une structure de type macroréseau, - les mélanges polymères/maltènes sont des systèmes bi-phasiques constitués par une phase de copolymère gonflé et une phase de maltènes, tandis que les mélanges polymères/asphaltes sont des systèmes tri-phasiques constitués d’une phase de copolymère gonflé, d’une phase de maltènes et d’une phase d’asphaltènes stabilisés par des maltènes. Dans tous les cas, ces effets sont la conséquence directe du gonflement du copolymère dans les mélanges. Cette étude a donc permis d’établir que la microstructure des copolymères a une influence notoire sur leur gonflement et sur les performances rhéologiques des mélanges résultants / A study of maltenes/polymer and asphalt/polymer blends, with two styrene-butadiene-styrene (SBS) polymers with four-branch star-like chain architecture is reported in this work. The employed polymers, with the same overall composition and distribution, were in-situ partially hydrogenated using a Nickel II Ziegler-Natta type catalyst without cross-linking or chain scission reactions. Blends were prepared by a melt mixing procedure and studied by fluorescence microscopy and rheological measurements. Results indicate that maltene/polymers blends are bi-phase heterogeneous systems with swollen polymer-rich and maltenes-rich phases, while asphalt/polymers blends are tri-phase systems with swollen polymer-rich, maltenes-rich and stabilized asphaltenes phases. In both cases, the rheological behavior of blends is mainly affected by the swollen polymer rich phase. It was confirmed that the rheological properties of PMM depend on the molecular characteristics of the copolymer such as the total molecular weight and molecular architecture, which determine the material behavior

No description available.

O muco protege o corpo humano de partículas externas, mas também representa uma barreira para a entrega de controlada de medicamentos através de nanocarregadores. Para ultrapassar a barreira do muco e impedir mucoadesão, nanopartículas sólidas são normalmente revestidas com polímeros inertes, tais como o polietileno glicol (PEG). No entanto, trata-se de um procedimento relativamente complexa. Nesta tese, estudamos métodos para fabricar nanocarreadores com uma excepcional combinação de propriedades, incluindo uma boa capacidade de mucopenetração e uma grande capacidade de carga. Ao contrário dos métodos convencionais de revestimento, usamos um copolímero dibloco, que consiste em dois blocos hidrofóbicos e hidrofílicos, que se auto-organiza em polimerosomos sob hidratação. Devido à inércia do bloco hidrofílico, estes polimerosomos devem ser, por natureza, muco penetradores. Além disso, sua estrutura oca fornece os polimersomos para serem carregados com carga hidrofílica, enquanto a carga hidrofóbica pode ser transportada através da membrana. Por conta da utilização de um polímero hidrolisável na presença de ácido, ácido poli láctico (PLA) como a espinha dorsal copolímero, demonstramos que estes polimerosomos podem liberar o conteúdo, após aplicação do estímulos externo relacionado ao pH. Os experimentos de rastreamento de partículas demonstraram que os polimersomos se difundem mais rápido do que as partículas não revestidas, em muco de intestino de porco, e testes de biodistribuição apresentaram resultados encorajadores para a entrega localizada de fármacos de maneira mais homogênea, melhorando a biodisponibilidade e efeitos terapeuticos. Mais estudos relacionados ao aumento da eficiência de encapsulação e testes de efetividade in vivo no tratamento de doenças devem ser promovidos. Acreditarmos que combinação das vantagens relacionadas à estrutura vesicular dos polimerossomas, estabilidade, e muco penetração possibilitam o desenvolvimento de uma nova plataforma para a entrega controlada de medicamentos na mucosa. / Mucus protects the human body by trapping foreign particulates but also poses a barrier for drug delivery by slowing down the mobility of drug carriers. To design mucus penetrating carriers, solid particles are typically coated with inert polymers such as polyethylene glycol (PEG) to prevent mucoadhesion. However, the solid structure of these particles limits their loading capabilities and the process to coat them requires a complex synthesis. In this thesis we studied methods to fabricate nanocarriers with an exceptional combination of properties including a good mucus-penetration capability and loading capacity of hydrophilic and hydrophobic cargos. Unlike conventional coating methods, we use a diblock copolymer, consisting of both hydrophobic and hydrophilic blocks, which self-assembles into polymersomes under hydration. Because of the inertness of the hydrophilic block, these polymersomes should be mucus-penetrating by nature. Moreover, their hollow structure provides the polymersomes to be loaded with hydrophilic cargo, whereas hydrophobic cargo can be carried through the membrane. Importantly, by using a hydrolysable acid-catalyzed polymer (poly lactic acid, PLA) as the copolymer backbone, we demonstrate that these polymersomes can release contents upon application of external pH stimuli. Particle Tracking experiments demonstrated that polymersomes diffuse faster than uncoated particles in porcine intestine mucus, and biodistribution tests displayed encouraging results towards more homogeneous local drug-delivery, helping bioavailability as well as therapeutic efects. More studies related to the increase of encapsulation efficiency, and in vivo disease treatment tests should be promoted. Although we believe that combining the advantages of polymersome carrier, and tunning the membrane composition, this mucus-penetrating carrier we propose may provide as a new platform for mucosal drug delivery.