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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Controlled Radical Polymerizations in Miniemulsions: Advances in the Use of RAFT

Russum, James 03 November 2005 (has links)
The goal of this work is to increase the current understanding of Controlled Radical Polymerizations (CRPs) in two areas. Progressing closer towards employing an aqueous system, specifically miniemulsion, to produce poly(vinyl acetate) via reversible addition fragmentation chain transfer (RAFT) chemistry constitutes the first part of this goal. Presented are the results of miniemulsion polymerizations using both water and oil-soluble initiators. Limiting conversions in both are examined and explained in terms of radical loss. The second part of the goal is to further the understanding of the nature of the RAFT/miniemulsion system when employed in continuous tubular reactors. The development of the recipe using mixed surfactants, the results of styrene homopolymerizations in batch and tube, and the results of a chain extension experiment demonstrating the living nature of the chains formed in the tubular reactor are presented. Kinetic anomalies are addressed, as well as polydispersity (PDI) differences between batch and tube. Flow phenomenon and their influence on residence time distribution and by implication the polydispersity of the polymer formed are offered as explanations for the variance in PDI and are subsequently quantified. A model of RAFT in laminar flow is presented and the results and implications are discussed in general terms. The flow profile of the reactor is examined using a tracer technique developed specifically for this system. Experiments are presented directly relating the residence time distribution to the polydispersity of the polymer. Transient behavior of the reactor in isolated plug flow is explained in terms of initiator loss. Both experimental data and a model are used to support this hypothesis. Finally, conclusions and implications are presented and unanswered questions and the ideas for future work that they generated are addressed.
2

Polymerization And Characterization Of Methylmethacrylate By Atom Transfer Radical Polymerization

Aran, Bengi 01 May 2004 (has links) (PDF)
In this work, methylmethacrylate, MMA was polymerized by ATRP method to obtain low molecular weight living polymers. The initiator was p-toluenesulfonylchloride and catalyst ligand complex system were CuCl-4,4&rsquo / dimethyl 2,2&rsquo / bipyridine. Polymers with controlled molecular weight were obtained. The polymer chains were shown by NMR investigation to be mostly syndiotactic. The molecular weight and molecular weight distribution of some polymer samples were measured by GPC method. The K and a constants in [h]=K Ma equation were measured as 9.13x10-5 and 0.74, respectively. FT-IR and X-Ray results showed regularity in polymer chains. The molecular weight-Tg relations were verified from results of molecular weight-DSC results.
3

Pyridine and amine functionalized polymers by anionic and controlled free radical polymerization methods

Ndawuni, Mzikayise Patrick 07 1900 (has links)
The synthesis of dipyridyl functionalized polysulfones with improved hydrophilicity, enhanced membrane morphology and excellent ATRP polymeric ligand properties was conducted by the following method: (a) the formation of lithiated polysulfone from unmodified polysulfone and the subsequent reaction with 2,2'-vinylidenedipyridine in tetrahydrofuran at -78 oC under argon atmosphere to afford the corresponding dipyridyl functionalized polysulfone. The stoichiometry of the reaction affects the degree of functionalization of the product. When equimolar amounts of 2,2'-vinylidenedipyridine are added to the lithiated polysulfone, the degree of functionalization obtained was 45%. However, the addition of 10% and 20% molar excess of 2,2'-vinylidenedipyridine to the corresponding lithiated polysulfone produced dipyridyl functionalized polysulfones with degrees of functionalization of 80% and 95%, respectively; and (b) the membranes obtained from unmodified polysulfone as well as dipyridyl functionalized polysulfones were characterized by atomic force microscopy, scanning electron microscopy, pure water permeation measurements and contact angle measurements. Amine chain end functionalized polystyrene and poly(methyl methacrylate) were prepared by Atom Transfer Radical Polymerization (ATRP) methods as follows: (a) •-Aminophenyl functionalized polystyrene was prepared in quantitative yields by ATRP methods using a new primary amine functionalized initiator adduct, formed in situ by the reaction of 1-(4-aminophenyl)-1-phenylethylene and (1-bromoethyl)benzene in the presence of copper (I) bromide/2,2'-bipyridyl as catalyst in diethyl ether at 110 oC, for the polymerization of styrene.(b) New •-bis(aminophenyl) and •,ω-tetrakis(aminophenyl) functionalized polymers were prepared in quantitative yields by the ATRP method using the following synthetic strategy: (i) the initiation of styrene polymerization with a new primary diamine functionalized initiator adduct, generated in situ by the reaction of stoichiometric amounts of 1,1-bis(4-aminophenyl)ethylene with (1-bromoethyl)benzene in the presence of copper (I) bromide/2,2'-bipyridyl as catalyst, afforded •-bis(aminophenyl) functionalized polystyrene; and (ii) •-bis(aminophenyl) functionalized poly(methyl methacrylate) was prepared by the ATRP method using the primary diamine functionalized initiator adduct as initiator for methyl methacrylate polymerization; and (iii) well defined •,ω-tetrakis(aminophenyl) functionalized polystyrene was prepared by the post ATRP chain end modification reaction of •-bis(aminophenyl) functionalized polystyrene with 1,1-bis(4-aminophenyl)-ethylene at the completion of the polymerization reaction. (c) Similarly, •-bis(4-dimethylaminophenyl) functionalized polystyrene was prepared by using a new tertiary diamine functionalized initiator adduct, formed in situ by treatment of equimolar amounts of 1,1-bis[(4-dimethylamino)phenyl]-ethylene with (1-bromoethyl)benzene in the presence of copper (I) bromide/2,2'-bipyridyl as the catalyst in diphenyl ether at 110 oC for the initiation of styrene polymerization by the ATRP method. Furthermore, the ATRP of methyl methacrylate, initiated by the new tertiary diamine functionalized initiator adduct, produced •-bis(4-dimethylaminophenyl) functionalized poly(methyl methacrylate). In addition, •,ω-tetrakis(4-dimethylaminophenyl) functionalized polystyrene was synthesized via a post ATRP chain end modification reaction of •-bis(4-dimethylaminophenyl) functionalized polystyrene with equimolar amounts of 1,1-bis[(4-dimethylamino)phenyl]ethylene at the completion of the polymerization process. vi Quantitative yields of the different amine functionalized polymers with predictable number average molecular weights (Mn = 1.3 x 103 – 16.4 x103 g/mol), narrow molecular weight distributions (Mw/Mn = 1.03 – 1.29) and controlled chain end functionality were obtained. Polymerization kinetics data was employed to determine the controlled/living character of each ATRP reaction leading to the formation of the different amine chain end functionalized polymers. The polymerization processes were monitored by gas chromatographic analyses. Polymerization kinetics measurements for all reactions show that the polymerizations follow first order rate kinetics with respect to monomer consumption. The number average molecular weight of the amine functionalized polymers increases linearly with percentage monomer conversion and polymers with narrow molecular weight distribution were obtained. The ATRP of styrene, catalyzed by a novel dipyridyl functionalized polysulfone/CuBr supported catalyst system, afforded well defined polystyrene with predictable number average molecular weight and narrow molecular weight distribution in a controlled/living free radical polymerization process. The substituted 1,1-diphenylethylene initiator precursor derivatives and the functionalized polymers were characterized by nuclear magnetic resonance spectrometry, fourier transform infrared spectroscopy, thin layer chromatography, column chromatography, size exclusion chromatography, non-aqueous titrations, differential scanning calorimetry and thermogravimetrical analysis. / Chemistry / M. Sc. (Chemistry)
4

Pyridine and amine functionalized polymers by anionic and controlled free radical polymerization methods

Ndawuni, Mzikayise Patrick 07 1900 (has links)
The synthesis of dipyridyl functionalized polysulfones with improved hydrophilicity, enhanced membrane morphology and excellent ATRP polymeric ligand properties was conducted by the following method: (a) the formation of lithiated polysulfone from unmodified polysulfone and the subsequent reaction with 2,2'-vinylidenedipyridine in tetrahydrofuran at -78 oC under argon atmosphere to afford the corresponding dipyridyl functionalized polysulfone. The stoichiometry of the reaction affects the degree of functionalization of the product. When equimolar amounts of 2,2'-vinylidenedipyridine are added to the lithiated polysulfone, the degree of functionalization obtained was 45%. However, the addition of 10% and 20% molar excess of 2,2'-vinylidenedipyridine to the corresponding lithiated polysulfone produced dipyridyl functionalized polysulfones with degrees of functionalization of 80% and 95%, respectively; and (b) the membranes obtained from unmodified polysulfone as well as dipyridyl functionalized polysulfones were characterized by atomic force microscopy, scanning electron microscopy, pure water permeation measurements and contact angle measurements. Amine chain end functionalized polystyrene and poly(methyl methacrylate) were prepared by Atom Transfer Radical Polymerization (ATRP) methods as follows: (a) •-Aminophenyl functionalized polystyrene was prepared in quantitative yields by ATRP methods using a new primary amine functionalized initiator adduct, formed in situ by the reaction of 1-(4-aminophenyl)-1-phenylethylene and (1-bromoethyl)benzene in the presence of copper (I) bromide/2,2'-bipyridyl as catalyst in diethyl ether at 110 oC, for the polymerization of styrene.(b) New •-bis(aminophenyl) and •,ω-tetrakis(aminophenyl) functionalized polymers were prepared in quantitative yields by the ATRP method using the following synthetic strategy: (i) the initiation of styrene polymerization with a new primary diamine functionalized initiator adduct, generated in situ by the reaction of stoichiometric amounts of 1,1-bis(4-aminophenyl)ethylene with (1-bromoethyl)benzene in the presence of copper (I) bromide/2,2'-bipyridyl as catalyst, afforded •-bis(aminophenyl) functionalized polystyrene; and (ii) •-bis(aminophenyl) functionalized poly(methyl methacrylate) was prepared by the ATRP method using the primary diamine functionalized initiator adduct as initiator for methyl methacrylate polymerization; and (iii) well defined •,ω-tetrakis(aminophenyl) functionalized polystyrene was prepared by the post ATRP chain end modification reaction of •-bis(aminophenyl) functionalized polystyrene with 1,1-bis(4-aminophenyl)-ethylene at the completion of the polymerization reaction. (c) Similarly, •-bis(4-dimethylaminophenyl) functionalized polystyrene was prepared by using a new tertiary diamine functionalized initiator adduct, formed in situ by treatment of equimolar amounts of 1,1-bis[(4-dimethylamino)phenyl]-ethylene with (1-bromoethyl)benzene in the presence of copper (I) bromide/2,2'-bipyridyl as the catalyst in diphenyl ether at 110 oC for the initiation of styrene polymerization by the ATRP method. Furthermore, the ATRP of methyl methacrylate, initiated by the new tertiary diamine functionalized initiator adduct, produced •-bis(4-dimethylaminophenyl) functionalized poly(methyl methacrylate). In addition, •,ω-tetrakis(4-dimethylaminophenyl) functionalized polystyrene was synthesized via a post ATRP chain end modification reaction of •-bis(4-dimethylaminophenyl) functionalized polystyrene with equimolar amounts of 1,1-bis[(4-dimethylamino)phenyl]ethylene at the completion of the polymerization process. vi Quantitative yields of the different amine functionalized polymers with predictable number average molecular weights (Mn = 1.3 x 103 – 16.4 x103 g/mol), narrow molecular weight distributions (Mw/Mn = 1.03 – 1.29) and controlled chain end functionality were obtained. Polymerization kinetics data was employed to determine the controlled/living character of each ATRP reaction leading to the formation of the different amine chain end functionalized polymers. The polymerization processes were monitored by gas chromatographic analyses. Polymerization kinetics measurements for all reactions show that the polymerizations follow first order rate kinetics with respect to monomer consumption. The number average molecular weight of the amine functionalized polymers increases linearly with percentage monomer conversion and polymers with narrow molecular weight distribution were obtained. The ATRP of styrene, catalyzed by a novel dipyridyl functionalized polysulfone/CuBr supported catalyst system, afforded well defined polystyrene with predictable number average molecular weight and narrow molecular weight distribution in a controlled/living free radical polymerization process. The substituted 1,1-diphenylethylene initiator precursor derivatives and the functionalized polymers were characterized by nuclear magnetic resonance spectrometry, fourier transform infrared spectroscopy, thin layer chromatography, column chromatography, size exclusion chromatography, non-aqueous titrations, differential scanning calorimetry and thermogravimetrical analysis. / Chemistry / M. Sc. (Chemistry)

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