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Philosophiae Doctor - PhD / A variety of nitrogen based dendritic ligands have been synthesized and used in copper mediated Atom Transfer Radical Polymerization (ATRP) of MMA. These ligands were derived from the commercially available Generation 1 polypropyleneimine dendrimer DAB-(NH2)4. The first set of ligands was synthesized by reacting DAB-(NH2)4 with aromatic aldehydes such as 2-pyridinecarboxyaldhyde and 4-t-butyl benzaldehyde to form imine functionalized dendrimers. Analogous secondary amine functionalized dendrimers were also synthesized by reducing the abovementioned imine functionalized dendrimers using sodium borohydride. The ligands produced were characterized by 13C / 1H NMR, and infra-red spectroscopy as well as elemental analysis to confirm its structure. The ligands were then used in copper mediated ATRP of MMA. The resulting polymer solutions were analyzed by Gas Chromatography (GC) to monitor the monomer conversion while the isolated polymers were analyzed by gel permeation chromatography (GPC) for molecular weight determination. Results showed that the primary and secondary amine and imine dendritic ligands were not efficient in promoting ATRP reactions. This led to the modification of DAB-(NH2)4 using methyl methacrylate to replace the peripheral amino groups of the DAB-(NH2)4 with tertiary amine groups. A second generation tertiary amine dendrimer was also synthesized in a similar fashion. The ligands obtained were then characterized using 13C and 1H NMR spectroscopy. The tertiary amine dendrimers were used in copper mediated ATRP of MMA. The polymerization medium was analyzed over time using GC to monitor monomer conversion while GPC was used for molecular weight determination of the resulting polymers. The results obtained using the methyl methacrylate modified ligands indicated that in the case of MMA polymerization, these ligands essentially conformed to the requirements of a good ATRP system. However in the preliminary studies, when employed in copper mediated ATRP of styrene, these ligands did not perform well. Further investigation is needed to improve the performance of these ligands in styrene polymerization under ATRP conditions. / South Africa

Living radical polymerization has proved to be a powerful tool for the synthesis of polymers as it allows for a high degree of control over the polymer microstructure and the synthesis of tailored molecular architectures. Although it has great potential, its use on an industrial scale is limited due to environmental and economical aspects. Nitroxide mediated polymerization is explored to bring this technology closer to adoption in commercial applications. One of the obstacles encountered using nitroxide mediated polymerization in microemulsion systems is the difficulty in controlling both the particle size and target molecular weight. Due to the nature of the formulation, a decrease in the target molecular weight is coupled to an increase in the particle size. For many applications, it is important to be able to design polymer particles with both specifications independently. Strategies to decouple these two properties and processing conditions required for targeting a range of particle sizes and molecular weights for n butyl acrylate latexes are presented. Furthermore, in an attempt to reduce the large amounts of surfactant typically used in microemulsions, these methods were explored at low surfactant to monomer ratios (0.2 to 0.5 by wt.) in order to reduce the costs associated with excess surfactant and post processing steps for surfactant removal (high surfactant levels also give poor water-resistance in coatings). Stable nanolatexes with particle sizes <40 nm have been obtained by other groups using NMP in microemulsions with SG1 but have done so by using much higher surfactant to monomer ratios (~2.5 by wt.) and at much lower solids content (6 10 wt. %). In this work, molecular weights of 20,000 to 80,000 g∙mol-1 were targeted and stable, n-butyl acrylate microemulsions with particle sizes ranging from 20 120 nm were prepared at a solids content of 20 wt. % using much lower surfactant concentrations. Although numerous studies have shown the effects of process parameters on particle sizes and methods to control the molecular weight, the decoupling of the molecular weight and particle size effect in NMP microemulsions under these conditions has not been done to this extent. In copolymer systems, nitroxide mediated polymerization also provides an efficient method to synthesize well defined block copolymers. Random copolymers are widely used as protective colloids, but the use of block copolymers for these applications has not been well studied. It is unclear what effects do the importance of a narrow molecular weight distribution and purity of block copolymers have on their performance as protective colloids. In order to investigate this, a range of block copolymers with different properties would need to be synthesized for systematic analysis. The direct synthesis of polystyrene b poly(acrylic acid) copolymers of varying lengths and compositions was successful by use of nitroxide mediated polymerization in bulk and solution polymerization. The characterization of these amphiphilic block copolymers was explored by titration and nuclear magnetic resonance spectroscopy. / Thesis (Master, Chemical Engineering) -- Queen's University, 2012-09-28 15:43:00.513

The basis for this research project is based on the discovery in the previous research that 2,2' ,5-trimethyl-3-( I-phenylethoxy)-4-tert-butyl-3-azahexane, (Styryl- TITNO) is able to control bulk polymerization of styrene at temperature as low as 70°C. The principle objective of this project was to evaluate the feasibility of using Styryl- TITNO to control radical solution and miniemulsion polymerizations at temperatures below 100°C. Styryl- TITNO was shown to effect solution polymerizations of both n-butyl acrylate (BA) and styrene below 100°C. Polymerization temperature was shown to be a crucial parameter for achieving control in Styryl- TITNO -mediated polymerizations. Good control of the number-average molecular weight (Mn) and molecular weight dispersity for the polymerization of BA was observed at 90°C. However, a lower temperature of 70 °C is required for good control of styrene polymerization. Living characteristics of polymer chains were demonstrated by a sequential chain extension of TITNO -terminated PBA with styrene at 90°C to form poly(n-butyl acrylate)- block-poly[(n-butyl acrylate)-co-styrene], [pBA-b-P(BA-co-PS)], block copolymers. An improvement in livingness in these reactions was observed when the second P(BAlstyrene) block was formed at 70°C after the first PBA block was produced at 90°C. Kinetics studies facilitated determination of the activation-deactivation equilibrium constant (K), which for styrene polymerization at 90°C (K = 4.1 x 10.9 mol L-J at 90°C and 3.0 x 10-9 mol L-J at 70 "C) is nearly an order of magnitude higher than that for BA polymerization at the same temperature (K = 8.5 x 10-11 mol L-I). This is the reason why BA polymerization shows better control than styrene polymerization at 90°C. The activation energy (Ea) for thermolysis of Stryl- TITNO is 104.1 kJ mol", which is relatively low compared to the literature values of Ea for various styryl alkoxymines. This explains why Styryl- TITNO is able to effect polymerization at temperatures as low as 70 "C. The studies of Styryl- TITNO-mediated miniemulsion polymerizations at 90 "C indicate that accumulation of free TITNO• in the particles is an issue for use of Styryl- TITNO in miniemulsion polymerizations. The use of L-ascorbic acid (L-AA) and L-ascorbic acid 6-palmitate (L-AAP) as nitroxide scavengers to reduce the level of free TITNO • in the polymerization was investigated. The best result was observed for the polymerization of BA in the presence of 5.35 mol% of L-AAP relative to Styryl- TITNO, which attained 48% conversion after 5 h. The chain extension of isolated TITNO -terminated PBA, TITNO -PBA, was used to examine the livingness of - polymer -chains before the rate of polymerization was severely retarded. The livingness of TITNO-PBA was evidenced by a shift of the staring PBA molecular weight distribution towards higher molecular weight, which provides solid evidence that the majority of polymer chains remained living. Thus, it can be concluded with certainty that the accumulation of free TITNO• was mainly responsible for the suppression of polymerization in miniemulsion polymerizations mediated by Styryl- TITNO.

Synthesis of novel amphiphilic copolymers based on sugar moieties: development of new architectures and biomedical applications As early as in the 50’s, amphiphilic copolymers started to attract much interest in the frame of polymer science thanks to their self-assemblies as organized nano-structures in a selective solvent. The resulting micelles or vesicles have emerged as potentially useful materials in the biomedical field such as drug delivery systems when matching the specific conditions of size, coating nature and functionalization,… Moreover, active cell-targeting increases the therapeutic effect by selectively delivering the drug to the required cells. Accordingly, carbohydrates have drawn much attention due to the cell recognition processes they can mediate. Carbohydrates are thus incorporated in polymer backbones to mimic the naturally occurring substrate for the adapted cell receptors. The originality of this thesis is based on the use of sugar moieties as potential multi-hydroxylated initiators for the polymerization of various lactones. This leads to well-defined amphiphilic polymer architectures along with the development of a more facile route for the incorporation of carbohydrates in polymer chains to promote active cell-targeting of the as-obtained nano-structures. The first part of the thesis aims at describing the synthesis of novel amphiphilic brush-like polymers via two pathways. A first approach relies upon the synthesis of polyester arms initiated from the alcohol groups of pending sugars distributed along a preformed hydrophilic polymethacrylate backbone obtained by controlled radical polymerization (via ATRP). Various metal-based and organic catalysts/activators have been studied to lead to the desired architectures using this “grafting from” technique. In another synthetic strategy, the lactone polymerization using a carbohydrate initiator has been carried out, followed by end-chain derivatization reactions yielding brush-like copolymers via a “grafting through” technique. Slight modifications of the end-chain functionalities have also afforded the possibility to synthesize amphiphilic mikto-arm copolymers which self-assemble in aqueous medium in micelles characterized by interesting size features affording promising applications as new drug delivery systems. On the other hand this thesis also focuses on the use of carbohydrate moieties in amphiphilic diblock copolymers such as poly(ε-caprolactone)-b-poly(methacrylate-graft-poly(ethylene oxide)-co-6-O-methacryloyl-D-galactopyranose) or poly(ε-caprolactone)-b-poly(methacrylate-graft-poly(ethylene oxide)-co-1-O-methacryloyl-D-mannofuranose), using the combination of lactone ring-opening polymerization with ATRP of the respective functionalized comonomers, followed by selective post-polymerization sugar deprotection. Next to these copolymers based on polylactones and polymethacrylates, fully degradable amphiphilic block copolymers composed of a polycarbonate backbone have been originally designed. To that end, a multi-step procedure involving the synthesis of sugar-substituted cyclic carbonates, block copolymerization reactions and ultimate selective sugar deprotection, has been investigated. The self-organization of the resulting copolymers, e.g., poly(trimethylene carbonate)-b-poly(3-O-(5’-methyl,5’-carboxy-1’,3’-dioxan-2’-one)-D-glucopyranose), has been studied in aqueous medium. Interestingly, the so-formed polymeric micelles proved to display remarkable living cell-targeting properties. Fabian Suriano

No description available.

Thesis (Ph.D.) -- McMaster University, 1998. / Includes bibliographical references. Also available via World Wide Web.

Thesis (Ph.D.)--McMaster University (Canada), 1994. / Source: Dissertation Abstracts International, Volume: 56-08, Section: B, page: 4349. Adviser: H. D. H. Stover.

Dissertation (Ph. D.)--University of Akron, Dept. of Chemical Engineering, 2005. / "August, 2005." Title from electronic dissertation title page (viewed 12/27/2005) Advisor, H. Michael Cheung; Committee members, J. Richard Elliott, Stephanie T. Lopina, A. Dhinojwala, Avraam I. Isayev; Department Chair, Steven S. Chuang; Dean of the College, George K. Haritos; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.