The Design, Synthesis and Testing of N-alkoxy Amine Initiators for Nitroxide-mediated 'living' Free Radical Polymerization PDF Download
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Author: Aaron Nilsen
Publisher:
ISBN:
Category :
Languages : en
Pages : 1088
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Author: Aaron Nilsen
Publisher:
ISBN:
Category :
Languages : en
Pages : 1088
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Author: Jean K. Ruehl
Publisher:
ISBN:
Category :
Languages : en
Pages : 990
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Author: Nicole Lyn Hill
Publisher:
ISBN:
Category :
Languages : en
Pages : 656
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Author: Anna C. Greene
Publisher:
ISBN:
Category : Amines
Languages : en
Pages : 438
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Author: Didier Gigmes
Publisher: Royal Society of Chemistry
ISBN: 1782622632
Category : Science
Languages : en
Pages : 513
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Nitroxide-mediated polymerization is an important branch of controlled radical polymerization, which has revolutionised the preparation of polymer architectures and compositions. This is the first book dedicated to the topic and covers the history and development of nitroxide-mediated polymerization, as well as current techniques of academic and industrial interest. Nitroxide-Mediated Polymerization gathers together and comprehensively discusses all aspects of nitroxide-mediated polymerization, from fundamental principles through to industrial applications. A specific focus will be dedicated to the principle of the technique, its kinetics aspects, the synthesis of the controlling agents, the range of polymerizable monomers, its potential for preparation of advanced organic and hybrid materials and its status at the industrial stage. The book details all stages of the field, with chapters detailing the history, recent developments and novel materials in this fast developing area. Edited and written by expert researchers working in the field and academia this book focuses on highlighting the kinetic aspects of nitroxide-mediated polymerization, providing insight into the kinetics that can sometimes be hard to follow in published papers. The book will be of interest to polymer chemists and materials scientists at graduate level and above.
Author: Sarav Bharat Jhaveri
Publisher:
ISBN:
Category :
Languages : en
Pages : 670
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Author:
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 868
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Author: William G. Skene
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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The work presented in this thesis deals primarily with living free radical polymerization (LFRP). Two main specific areas of this process have been studied; thermal and photochemical reaction sequences. Stoichiometric unimolecular initiators were found to be ideal probes for studying the reactions involved in the LFRP process. The bond dissociation energy (BDE) of the labile C-O bond of the alkoxyamine initiators was found to be ca. 28 kcal/mol and is dependent on the resulting carbon centered radical produced upon thermal decomposition. Lower activation energies were measured for more stable carbon centered radicals. Complementary to the thermal studies, photoacoustic studies (PAC) involving photochemical decomposition of the initiators led to the homolytic N-O and C-O bond cleavages in addition to disproportionation product formation. The BDE for the N-O bond of these initiators is ca. 43 kcal/mol. These studies also provided insight into volume effects, where a strict homologous solvent series is not required for extrapolating true enthalpies of reactions and volume correction factors for PAC. The decomposition quantum yields of a series of ketone based actinometers used for PAC BDE studies were re-evaluated and found to be solvent independent. The specific kinetics of thermal LFRP were equally investigated through the use of probes which are normally used for thermal initiation. Fast time resolved techniques of laser flash photolysis (LFP) were used to measure the bi-molecular rate constant for the coupling reaction between a carbon centered radical and a nitroxide radical involved in LFRP. Typical values lay in the area of 108 M-1 s-1 and are influenced by the structure of the carbon centered radical and not that of the nitroxide. The rate constants were observed to be slower with more stable carbon centered radicals, similar to the BDE results where weaker dissociation energies were observed. The formation of minor disproportionation products upon thermal decomposition of the unimolecular initiators was assigned to a concerted four center elimination ultimately responsible for the lack of controlled polymerization with acrylates. The incorporation of steric effects into the monomer or the nitroxide suppressed the formation of these products by increasing the energy barrier necessary for correct orbital alignment required for the elimination reaction. Living polymerization of acrylate monomers was achieved with a nitroxide containing bulky substituents in its 2 and 6 positions. Moderate success of living polymerization was also achieved with acrylate type monomers through the use of an additional phase not miscible with the bulk phase. Chromophores producing triplet states upon excitation were found to undergo fast and efficient energy transfer to a covalently linked alkoxyamine subsequently promoting C-O bond homolysis. The orientation of the C-O bond relative to the chromophore in addition to the distance separating the two influences the efficiency of energy transfer and bond cleavage. Using a benzophenone type chromophore with a covalently linked alkoxyamine initiator promoted photoinduced living type polymerization of acrylate.
Author: Omari E Ansong
Publisher:
ISBN:
Category :
Languages : en
Pages : 153
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A number of nitroxide adducts and N-acyloxytrialkylammonium salts were prepared, isolated, characterized and evaluated as initiators for the controlled and living free radical polymerization of methacrylate and dimethacrylate monomers under mildly thermal and photochemical conditions. The initiators and polymerization methods that were developed could potentially be used for improving resins employed in dental applications. Using very easy synthesis strategies, the following nitroxide initiators were prepared in high purity, isolated and characterized: 1-Benzoylperoxy-2,2,6,6-tetramethyl-piperidine (BPO/TEMPO), 1-(2'-Cyano-2'-propoxy)-2,2,6,6-tetramethylpiperidine (AIBN/TEMPO), 1,1-ditertbutyl-1-(1-methyl-1-cyanoethoxy)-amine (AIBN/DBN), 1,1-ditertbutyl-1-(benzoylperoxy)-amine (BPO/DBN) and 2,2,6,6,-tetramethyl-4-oxo-1-(1-methyl-1-cyanoethoxy)-piperidine (AIBN/4-OXO-TEMPO). Using H2SO4 additive and an improved unimolecular initiation in nitroxide mediated polymerization, living and controlled polymerization of methyl methacrylate (MMA), tri-ethylene glycol dimethacrylate (TEGDMA) and ethoxylated bisphenol A dimethacrylate (EBPADMA) were accomplished, for the first time ever for most of the initiators. Linear polymers (PMMA) were produced in high yield (93 %) under mildly thermal conditions (T = 70 oC) and with excellent attributes: (PDI = 1.04-1.26), Mn (87000), Tg (122-128 oC), Td (290-410 oC). Highly crosslinked polymers, poly(TEGDMA) and poly(EBPADMA), were produced in high yield (100 %) with Td (350-400 oC). The initiators were stable for a year and half at 0 oC. Two routes were investigated for the preparation of N-acyloxytrialkylammonium salts. The more efficient of these routes was used to make several novel analogs of the salts. The salts were evaluated for the free radical polymerization of MMA, TEGDMA and EBPADMA under mildly thermal (T = 60 oC) conditions with and without H2SO4 additive. Polymerization rate, yield and polymer attributes all improved upon application of H2SO4 additive. PMMA was produced with excellent attributes (PDI = 1.01-1.06), Mn (96,000-122000), Td (330-385) and Tg (127-134). Highly crosslinked poly(TEGDMA) and poly(EBPADMA) were produced with Td ranges of 300-374 oC and 375-411 oC respectively.
Author: MariEllen Cottman
Publisher:
ISBN:
Category :
Languages : en
Pages : 192
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