[PDF] Synthesis And Evaluation Of Alkoxyamine Initiators For Nitroxide Mediated Polymerization eBook

Author : Didier Gigmes
Publisher : Royal Society of Chemistry
Page : 512 pages
File Size : 27,89 MB
Release : 2016
Category : Science
ISBN : 1782620613

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The first book dedicated to nitroxide-mediated polymerization and covers the history and development of NMP, as well as current techniques of academic and industrial interest.

Author : Jennifer Marie Petraitis
Publisher :
Page : 95 pages
File Size : 44,86 MB
Release : 2017
Category :
ISBN : 9781369701517

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Three novel fluorinated alkoxyamines were synthesized for nitroxide-mediated precipitation polymerization (NMP) of styrene in supercritical carbon dioxide. The polymerizations were conducted in supercritical carbon dioxide without excess free nitroxide to allow for a detailed study on nitroxide partitioning. The addition of a fluorinated moiety allowed for increased partitioning relative to the parent nitroxide into supercritical carbon dioxide. The loss of control over the polymerization due to nitroxide partitioning did not have a significant influence on the polymerization rate. Synthesis of polyfluorinated macroinitiators by atom transfer radical polymerization (ATRP) of fluorinated monomers was explored but thwarted due to a lack of solubility. The increased fluorine content due to polymerization of fluorinated monomers would have allowed direct control over the quantity of fluorine added to the macroinitiator and potentially influenced the quantity of nitroxide partitioning.

Author : Olivier Ouari
Publisher : Royal Society of Chemistry
Page : 611 pages
File Size : 14,88 MB
Release : 2021-05-13
Category : Science
ISBN : 1788019660

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Nitroxides are versatile small organic molecules possessing a stabilised free radical. With their unpaired electron spin they display a unique reactivity towards various environmental factors, enabling a diverse range of applications. They have uses as synthetic tools, such as catalysts or building blocks; imaging agents and probes in biomedicine and materials science; for medicinal antioxidant applications; and in energy storage. Polynitroxides (polymers bearing pendant nitroxide sidechains) have been used in organic radical batteries, oxidation catalysts and in exchange reactions for constructing complex architectures. Chapters in this book cover the synthesis of nitroxides, EPR studies and magnetic resonance applications, physiochemical studies, and applications including in batteries, imaging and organic synthesis. With contributions from leaders in the field, Nitroxides will be of interest to graduate students and researchers across chemistry, physics, biology and materials science.

Author : Chi Zhang
Publisher :
Page : pages
File Size : 28,6 MB
Release : 2014
Category :
ISBN :

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"Stimuli-responsive polymers have been touted as "smart" due to their fast and reversible responses to environmental changes. It is imperative for these polymers to have well-defined structures so that their performance can be consistent and predictable. In order to achieve this, nitroxide mediated polymerization (NMP) was employed as the synthesis technique for the microstructured polymers that form the core of the investigations presented in this thesis. As one of the main controlled radical polymerization techniques, NMP stands out for its simplicity in both required ingredients and purification procedures. Many known stimuli-responsive polymers are poly(methacrylates). However, homopolymerization of methacrylates has been challenging for NMP mainly due to the large equilibrium constant that resulted in high concentration of active radicals and thus excessive irreversible terminations. By using a small amount of "controlling co-monomer" such as styrene, copolymerizations with methacrylate-rich feeds can be controlled using the commercially available alkoxyamine initiator BlocBuilderTM via NMP, featuring linear increases in number average molecular weight versus conversion, and narrow molecular weight distribution.In this thesis, two methacrylates, namely 2-(dimethylamino)ethyl methacrylate (DMAEMA) and benzyl methacrylate (BzMA), whose homopolymers exhibit LCST-type phase separation behaviours in aqueous and ionic liquid (IL) solutions, respectively, were copolymerized with various controlling co-monomers by NMP to demonstrate the versatility of NMP in tuning thermo-responsive properties. For both methacrylates, styrene was initially used as the controlling co-monomer to obtain copolymers with relatively narrow molecular weight distribution and ability to extend chains to form block copolymers when reinitiated with a fresh batch of monomer. 2-Vinylpyridine (2VP) was then chosen to copolymerize with DMAEMA for its lower hydrophobicity compared to styrene and pH-sensitivity, where about 2 - 5 mol% 2VP was shown sufficient to obtain well-defined DMAEMA/2VP copolymers. The detailed phase behaviour characterization of these DMAEMA-rich copolymers in aqueous solutions revealed the effects of important factors such as pH, copolymer composition, solution concentration and polymer microstructure, on the tuning of transition temperatures.For BzMA, 9-(4-vinylbenzyl)-9H-carbazole (VBK) was used as an alternative controlling co-monomer. Controlled and pseudo-"living" copolymerizations were achieved with as little as 2 mol% VBK in the feed, demonstrating significant improvement compared to the BzMA/styrene system. The incorporation of fluorescent VBK resulted in 5-fold fluorescence enhancement during the phase separation of BzMA/VBK copolymers from IL [C2mim][NTf2]. The enhancement resulted from heightened efficiency of the fluorescence resonance energy transfer (FRET) between BzMA and VBK during aggregation. However, the solvatophobicity of VBK also significantly reduced the solubility of BzMA/VBK copolymers in the IL and rendered the phase separation irreversible. Further investigation on the effects of solvatophilicity and chain mobility on phase separation and reversibility in ILs was carried out by incorporating varying amounts of solvatophilic co-monomer, namely methyl methacrylate (MMA) and oligo(ethylene glycol) methacrylate (OEGMA), yielding BzMA/MMA/VBK and BzMA/OEGMA/VBK terpolymers. It was found that molecular weight, glass transition temperature, and solution concentration all played important roles on phase separation temperature but sufficiently high solvatophilicity (quantified by the concentration of solvatophilic group) was essential to facilitate the re-dissolution process after phase separation. " --