An unprecedented comprehensive study of ammonium and phosphonium polyelectrolytes probed and examined structure-property relationships with a focus on different macromolecular properties. Conventional free radical polymerization readily generated a large library of ammonium- and phosphonium-containing polyelectrolytes. Along with the two different cationic atoms, the alkyl substituent lengths and counterions were varied to generate a thorough structure-property relationship analysis. Phosphonium macromolecules displayed improved thermal stabilities and improved ionic conductivities compared to ammonium analogs. Longer alkyl substituent lengths systematically decreased the glass transition temperatures of all polyelectrolytes; the larger, bulkier counterions also resulted in lower glass transition temperatures. Counterion also impacted the thermal stability of the polymerized ionic liquids with less basic counterions leading to improved thermal stability. For the first time, the efficacy of phosphonium macromolecules for nonviral nucleic acid delivery was examined. Phosphonium macromolecules more efficiently complexed nucleic acids than ammonium analogs and butyl-containing phosphonium macromolecules delivered nucleic acids more effectively than the ammonium analog. Controlled radical polymerization generated unprecedented phosphonium-containing diblock copolymers and these diblock copolymers displayed enhanced colloidal stability and lower cytotoxicity compared to the phosphonium homopolymer for nucleic acid delivery. Step-growth polymerization techniques enabled the synthesis of well-defined, high molecular weight phosphonium ionenes for the first time. Phosphonium ionenes exhibited higher thermal stability and alkaline stability compared to ammonium ionenes. Due to their high thermal stability and relatively low glass transition temperatures, unprecedented melt rheology studies on polyelectrolytes probed the melt flow characteristics of phosphonium ionenes. Novel phosphonium gemini surfactants displayed interesting solution properties in aqueous and chloroform solutions. Electrospinning of the phosphonium gemini surfactants created uniform fibers. The synthesis and characterization of sulfonium polyelectrolytes enabled the first examination of sulfonium macromolecules for nonviral nucleic acid delivery. Sulfonium polyelectrolytes successfully bound nucleic acids and delivered them in vitro. Controlled radical polymerization generated innovative AB diblock and ABA triblock copolymers that displayed salt- and temperature-responsive properties suitable for biological applications such as drug delivery vehicles and hydrogels. Finally, adenine-containing polyelectrolytes were synthesized and they were successfully electrospun to generate adenine-decorated nanofibers appropriate for filtration and nonwoven applications. / Ph. D.

The objective of this thesis is to investigate well-defined cross-linked particles synthesized via the reversible addition fragmentation chain transfer (RAFT) process that can be used for drug delivery. To achieve this aim, a wide range of cross-linked micelle systems have been synthesized and intensively investigated. Various biocompatible monomers were employed, including poly (ethylene glycol) methyl ether methacrylate, 2-hydroxyl ethyl acrylate, functionalized glucosamine and nucleotides containing monomers. Different cross-linked structures were used, for example, core-cross-linked, nexus-cross-linked and shell-cross-linked micelles. Diverse stimuli-responsive particles were used, such as pH-sensitive, thermo-sensitive and thiol-sensitive cross-linked systems. Evidences of the successful synthesis of all the resulting cross-linked products are given. They displayed better properties, as drug carriers, than non-cross-linked micelles. A thermo-responsive seven-arm star glycopolymer, synthesized via the RAFT process, was also investigated.

No description available.

The objective of this thesis is to investigate well-defined cross-linked particles synthesized via the reversible addition fragmentation chain transfer (RAFT) process that can be used for drug delivery. To achieve this aim, a wide range of cross-linked micelle systems have been synthesized and intensively investigated. Various biocompatible monomers were employed, including poly (ethylene glycol) methyl ether methacrylate, 2-hydroxyl ethyl acrylate, functionalized glucosamine and nucleotides containing monomers. Different cross-linked structures were used, for example, core-cross-linked, nexus-cross-linked and shell-cross-linked micelles. Diverse stimuli-responsive particles were used, such as pH-sensitive, thermo-sensitive and thiol-sensitive cross-linked systems. Evidences of the successful synthesis of all the resulting cross-linked products are given. They displayed better properties, as drug carriers, than non-cross-linked micelles. A thermo-responsive seven-arm star glycopolymer, synthesized via the RAFT process, was also investigated.

No description available.

Aggregation-induced emission (AIE) is a phenomenon with many applications, such as chemical sensors, biological probes, immunoassay markets, and active layers in fabricating organic light-emitting diodes. AIE materials in polymers can enhance the emissivity of such materials while having the benefits of polymeric materials. This thesis examines the use of AIE polymers to study the effect of structure on the properties. This is done by first synthesizing a monomer with AIE characteristics, tetraphenylethylene-methacrylate (TPEMA). Secondly, polymerizing TPEMA using free and controlled radical polymerizations. Finally, the copolymerization of TPEMA with methyl methacrylate (MMA) to understand the effect of spaced-out TPE groups in the polymer chain on the photoluminescence of the polymer. The structures of all intermediates and final products were characterized by nuclear magnetic resonance (NMR) and size exclusion chromatography (SEC). The AIE characteristics were proven and compared using the photoluminescence graphs, showing that the homopolymer had increased emission intensity than its monomer. The copolymer had higher emission intensity than TPEMA and higher normalized emission intensity than that of the homopolymer, showing the effect of structure on the photoluminescence. Both the homopolymer and the copolymer were easier to aggregate than the monomer, making it more effective to utilize the material in applications where it needs to be emissive in diluted solutions. The glass transition temperature and the tacticity of the homopolymer and copolymer were also compared. The thesis is divided into the following five chapters; 1. Introduction, where a brief background along with the scope of the thesis is provided; 2. Literature Review, where a summary of controlled radical polymerization and AIE is given; 3. Experimental Section, where the materials' detailed procedure and characterization are provided; 4. Results and Discussion, where results of successful experiments are discussed; 5. Concluding Remarks, where the results are summarized, and future work is discussed.

Thesis (MSc (Chemistry and Polymer Science))--Stellenbosch University, 2008. / The Reversible addition fragmentation chain transfer (RAFT) technique is a robust and versatile technique that enables the synthesis of polymers of controlled molecular weight and polydispersity. The application of the RAFT technique in heterogeneous aqueous media has attracted great interest in academics and industry due to it being more environmentally friendly, besides its other advantages. To date, the synthesis of well-defined high molecular weight polymers via the RAFT process under industrially relevant conditions still remains a challenge for polymer chemists. The study addresses the application of the RAFT process in heterogeneous media, namely in miniemulsion polymerization, for the synthesis of AB diblock copolymers of n-butyl methacrylate and styrene. AB diblock copolymers of high molecular weight were successfully prepared via a twostep method. In the first step, a dithiobenzoate monofunctional RAFT agent was used in bulk polymerization with the first monomer, n-butyl methacrylate. After the polymerization, the majority of the polymer chains contained the thiocarbonyl-thio RAFT agent functionality, which makes the chains potentially active for chain extension. The polymeric RAFT agent (also referred to as the starting block) obtained in the first step was chain extended in the second step, in miniemulsion, upon further addition of fresh initiator and the second monomer, styrene. The effects of the initiator/RAFT agent concentration ratio on the miniemulsion systems were investigated. The miniemulsion systems used for the high molecular weight AB diblock copolymers exhibited living features despite the high polydispersity indices. Kinetic results showed an increase in the rate of polymerization throughout the polymerization. Size exclusion chromatography (SEC) results indicated significant broadening in the molecular weight distributions and a steep increase in the polydispersity during the polymerization. It was concluded that the broad molecular weight distributions and steep increase in the polydispersity was not only related to the initiator concentration but possibly due to other factors such as inhomogeneity in the miniemulsion system and a transition in the kinetic behavior during the polymerization. Secondary particle formation emerged from kinetic data and transmission electron microscopy (TEM) results, but this were not supported by the SEC results. The effect of the use of a water-soluble initiator on the miniemulsion system was also investigated. Results indicated a similar behavioral pattern as observed in the AIBNinitiated systems, and not much improvement in terms of the molecular weight distributions and polydispersity was seen. The effect of the molecular weight of the diblock copolymers on the miniemulsion system was investigated. Poly(n-butyl methacrylate)-b-poly(styrene) diblock copolymers of lower molecular weight were synthesized via the two-step process. Kinetic results indicated a similar behavioral trend as to that of the high molecular weight diblock copolymers synthesized, however SEC chromatograms showed narrower molecular weight distributions and low polydispersity indices.

En raison des propriétés redox réversibles du ferrocène et de son activité antibactérienne, les polymères à base de ferrocène sont intéressants pour synthétiser de nouveaux liants pour des revêtements anti-adhésifs bactériens. Cette étude rend compte de l’homopolymérisation et de la copolymérisation de monomères méthacryliques porteurs de groupes ferrocényles avec le méthacrylate de lauryle (LM). Le méthacrylate de méthylferrocène (FMMA) mais aussi quatre nouveaux monomères nommés méthacrylate de 2- ferrocénylméthoxyéthyle (FMOEMA), méthacrylate de 3-ferrocénylméthoxypropyle (FMOPMA), 4- ferrocénylméthoxybutyle (FMOBMA) et de 2-ferrocénylméthoxyméthyléthyle (FMOMEMA) ont d’ bord été synthétisés et ensuite polymérisés via le procédé RAFT. Les cinétiques ’homopolymérisation ont été étudiées par RMN 1H in situ. La polymérisation a été contrôlée en utilisant le 2-cyanoprop-2-yl dithiobenzoate (CPDB) comme agent de transfert de chaîne, à 70°C, dans le toluène deutéré. Ces monomères contenant le groupement ferrocényle se sont révélés très réactifs via le procédé RAFT, conduisant à des conversions de 96% et à des polymères de faibles indices de polymolécularité (Ð<1,6). La conversion des monomères suit une cinétique de premier ordre (jusqu’à 80%) avec une augmentation linéaire de la masse molaire en fonction de la conversion en monomère. En utilisant le monomère FMMA comme référence, l’ spacement entre la partie polymérisable et le groupement ferrocényle a été augmenté pour le FMOEMA, FMOPMA, FMOMEMA et FMOBMA afin d’ méliorer la mobilité des groupements latéraux. Cette mobilité se traduit par une diminution notable des températures de transition vitreuse des homopolymères entre le pFMMA et le pFMOBMA. De plus, les copolymères diblocs préparés par voie séquencée présentent deux températures de transition vitreuse spécifiques à chaque bloc, démontrant une incompatibilité de ces derniers. Les propriétés électrochimiques des monomères et celles des polymères ont été caractérisées par voltampérométrie cyclique. Enfin, les propriétés anti-adhésives de ces homopolymères et copolymères diblocs vis-à-vis d’une bactérie marine ont été évaluées. / Due to the reversible redox properties of ferrocene and its antibacterial activity, ferrocenyl-based polymers are useful for the synthesis of new anti-adhesive binders for marine antifouling coatings. This study reports the homopolymerization and copolymerization with lauryl methacrylate of ferrocenyl-based methacrylic monomers. Ferrocenylmethyl methacrylate (FMMA) as well as four novel monomers, namely 2- (ferrocenylmethoxy)ethyl methacrylate (FMOEMA), 3-(ferrocenylmethoxy)propyl methacrylate (FMOPMA),4-(ferrocenylmethoxy)butyl methacrylate (FMOBMA) and 2-(ferrocenylmethoxy)methylethyl methacrylate (FMOMEMA) were first synthesized, and subsequently polymerized by the RAFT process. The homopolymerization kinetics were investigated by in situ NMR. The radical polymerization was controlled by using 2-cyanoprop-2-yl dithiobenzoate (CPDB) as a chain transfer agent, at 70 °C in deuterated toluene. These monomers containing a ferrocenyl moiety with alcoxy linkers were found to be as reactive as FMMA in RAFT polymerization, resulting in conversions of 96% and in polymers with low dispersities (ÐM < 1.6). Monomer conversion follows a first order kinetics (up to 80%) with a linear increase in the molecular mass as a function of the monomer conversion. By using the FMMA monomer as a reference, the length of the alcoxy linker between the ferrocene unit and the backbone was increased for FMOEMA, FMOPMA, FMOMEMA and FMOBMA to improve the mobility of the side groups. This increase in macromolecular mobility led to a significant decrease of glass transition temperatures of the homopolymers. In addition, diblock copolymers exhibited two glass transition temperatures indicating that the two blocks are incompatible. The electrochemical properties of the monomers and those of the polymers were characterized using cyclic voltammetry. Finally, the anti-adhesive properties of these homopolymers and diblock copolymers toward marine bacteria were evaluated.

See attached files.

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