The Experts below are selected from a list of 59055 Experts worldwide ranked by ideXlab platform
Leonie Barner - One of the best experts on this subject based on the ideXlab platform.
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Self-Reporting Fluorescent Step-Growth RAFT Polymers Based on Nitrile Imine-Mediated Tetrazole-ene Cycloaddition Chemistry
2017Co-Authors: Diego Estupiñán, Thomas Gegenhuber, James P. Blinco, Christopher Barner-kowollik, Leonie BarnerAbstract:We introduce an inherently fluorescent self-reporting step-Growth Polymer system as well as a fluorescence-based methodology for accessing the kinetics of the underpinning photoinduced nitrile imine-mediated tetrazole-ene cycloaddition (NITEC) process, using an equimolar mixture of a bismaleimide linker and a bifunctional α,ω-tetrazole-chain transfer agent (CTA). Similarly, α,ω-tetrazole-capped polystyrene, prepared via RAFT Polymerization, was employed as a photoreactive macromonomer. Upon UV irradiation, the tetrazole moiety readily reacts with activated dialkenes producing the fluorescent pyrazoline-containing Polymer. Thus, the fluorescence emission of the step-Growth Polymers is directly correlated with the number of ligation points in the Polymer, forming an ideal self-reporting sensor system. The viability of the fluorescence-based quantification is verified via NMR spectroscopy, evidencing that fluorescence-based Polymerization monitoring is a viable avenue in cases where NMR spectroscopy is difficult to conduct
Barner-kowollik Christopher - One of the best experts on this subject based on the ideXlab platform.
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Self-reporting fluorescent step-Growth RAFT Polymers based on nitrile imine-mediated tetrazole-ene cycloaddition chemistry
'American Chemical Society (ACS)', 2017Co-Authors: Estupinan Diego, Gegenhuber Thomas, Blinco James, Barner-kowollik Christopher, Barner LeonieAbstract:We introduce an inherently fluorescent self-reporting step-Growth Polymer system as well as a fluorescence-based methodology for accessing the kinetics of the underpinning photoinduced nitrile imine-mediated tetra-zole-ene cycloaddition (NITEC) process, using an equimolar mixture of a bismaleimide linker and a bifunctional alpha,omega- tetrazole-chain transfer agent (CTA).Similarly, alpha,omega-tetrazole-capped polystyrene, prepared via RAFT Polymerization, was employed as a photoreactive macromonomer. Upon UV irradiation, the tetrazole moiety readily reacts with activated dialkenes producing the fluorescent pyrazoline-containing Polymer. Thus, the fluorescence emission of the step-Growth Polymers is directly correlated with the number of ligation points in the Polymer, forming an ideal self-reporting sensor system. The Viability of the fluorescence-based quantification is verified via NMR spectroscopy, evidencing that fluorescence-based Polymerization monitoring is a viable avenue in cases where NMR spectroscopy is difficult to conduct
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Fusing light-induced step-Growth processes with RAFT chemistry for segmented coPolymer synthesis : a synergetic experimental and kinetic modeling study
'American Chemical Society (ACS)', 2017Co-Authors: Gegenhuber Thomas, De Keer Lies, Goldmann Anja, Van Steenberge Paul, Mueller Jan, Reyniers Marie-françoise, Menzel Jan, D'hooge Dagmar, Barner-kowollik ChristopherAbstract:We pioneer the synthesis of well-defined high molar mass segmented coPolymers, employing a unique combination of step-Growth and reversible addition−fragmentation chain transfer (RAFT) Polymerization. The step-Growth precursor Polymer is obtained via the ambient temperature UV-light-induced Diels−Alder reaction of 6′-(propane-1,3- diylbis(oxy))bis(2-methylbenzaldehyde) (AA monomer) and di(isopropionic ethyl ester fumarate) trithiocarbonate (BB monomer). Unconventional off-stoichiometric conditions (r = [AA]0:[BB]0 = 1.5−1.75) are employed to ensure a sufficiently high incorporation of BB in the step-Growth product (1200 ≤ Mn/g mol−1 ≤ 3950). The optimum r value is based on a detailed product distribution analysis, comparing experimental and bivariate kinetic Monte Carlo generated data, using a scheme of over 200 reactions. The analysis highlights the unexpected occurrence of AA homoPolymerization and the ligation of the resulting AA segments at higher reaction times. The precursor step-Growth Polymer is successfully transformed into a segmented coPolymer via insertion of styrene by RAFT Polymerization at 60 °C (11 200 ≤ Mn/g mol−1 ≤ 53 400), as confirmed both experimentally and through simulations
Barner Leonie - One of the best experts on this subject based on the ideXlab platform.
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Self-reporting fluorescent step-Growth RAFT Polymers based on nitrile imine-mediated tetrazole-ene cycloaddition chemistry
'American Chemical Society (ACS)', 2017Co-Authors: Estupinan Diego, Gegenhuber Thomas, Blinco James, Barner-kowollik Christopher, Barner LeonieAbstract:We introduce an inherently fluorescent self-reporting step-Growth Polymer system as well as a fluorescence-based methodology for accessing the kinetics of the underpinning photoinduced nitrile imine-mediated tetra-zole-ene cycloaddition (NITEC) process, using an equimolar mixture of a bismaleimide linker and a bifunctional alpha,omega- tetrazole-chain transfer agent (CTA).Similarly, alpha,omega-tetrazole-capped polystyrene, prepared via RAFT Polymerization, was employed as a photoreactive macromonomer. Upon UV irradiation, the tetrazole moiety readily reacts with activated dialkenes producing the fluorescent pyrazoline-containing Polymer. Thus, the fluorescence emission of the step-Growth Polymers is directly correlated with the number of ligation points in the Polymer, forming an ideal self-reporting sensor system. The Viability of the fluorescence-based quantification is verified via NMR spectroscopy, evidencing that fluorescence-based Polymerization monitoring is a viable avenue in cases where NMR spectroscopy is difficult to conduct
Gegenhuber Thomas - One of the best experts on this subject based on the ideXlab platform.
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Self-reporting fluorescent step-Growth RAFT Polymers based on nitrile imine-mediated tetrazole-ene cycloaddition chemistry
'American Chemical Society (ACS)', 2017Co-Authors: Estupinan Diego, Gegenhuber Thomas, Blinco James, Barner-kowollik Christopher, Barner LeonieAbstract:We introduce an inherently fluorescent self-reporting step-Growth Polymer system as well as a fluorescence-based methodology for accessing the kinetics of the underpinning photoinduced nitrile imine-mediated tetra-zole-ene cycloaddition (NITEC) process, using an equimolar mixture of a bismaleimide linker and a bifunctional alpha,omega- tetrazole-chain transfer agent (CTA).Similarly, alpha,omega-tetrazole-capped polystyrene, prepared via RAFT Polymerization, was employed as a photoreactive macromonomer. Upon UV irradiation, the tetrazole moiety readily reacts with activated dialkenes producing the fluorescent pyrazoline-containing Polymer. Thus, the fluorescence emission of the step-Growth Polymers is directly correlated with the number of ligation points in the Polymer, forming an ideal self-reporting sensor system. The Viability of the fluorescence-based quantification is verified via NMR spectroscopy, evidencing that fluorescence-based Polymerization monitoring is a viable avenue in cases where NMR spectroscopy is difficult to conduct
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Fusing light-induced step-Growth processes with RAFT chemistry for segmented coPolymer synthesis : a synergetic experimental and kinetic modeling study
'American Chemical Society (ACS)', 2017Co-Authors: Gegenhuber Thomas, De Keer Lies, Goldmann Anja, Van Steenberge Paul, Mueller Jan, Reyniers Marie-françoise, Menzel Jan, D'hooge Dagmar, Barner-kowollik ChristopherAbstract:We pioneer the synthesis of well-defined high molar mass segmented coPolymers, employing a unique combination of step-Growth and reversible addition−fragmentation chain transfer (RAFT) Polymerization. The step-Growth precursor Polymer is obtained via the ambient temperature UV-light-induced Diels−Alder reaction of 6′-(propane-1,3- diylbis(oxy))bis(2-methylbenzaldehyde) (AA monomer) and di(isopropionic ethyl ester fumarate) trithiocarbonate (BB monomer). Unconventional off-stoichiometric conditions (r = [AA]0:[BB]0 = 1.5−1.75) are employed to ensure a sufficiently high incorporation of BB in the step-Growth product (1200 ≤ Mn/g mol−1 ≤ 3950). The optimum r value is based on a detailed product distribution analysis, comparing experimental and bivariate kinetic Monte Carlo generated data, using a scheme of over 200 reactions. The analysis highlights the unexpected occurrence of AA homoPolymerization and the ligation of the resulting AA segments at higher reaction times. The precursor step-Growth Polymer is successfully transformed into a segmented coPolymer via insertion of styrene by RAFT Polymerization at 60 °C (11 200 ≤ Mn/g mol−1 ≤ 53 400), as confirmed both experimentally and through simulations
As Weller - One of the best experts on this subject based on the ideXlab platform.
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The dehydroPolymerization of H3B•NMeH2 to form polyaminoboranes using [Rh(Xantphos–alkyl)] catalysts
'American Chemical Society (ACS)', 2017Co-Authors: Gm Adams, Al Colebatch, Jt Skornia, Ai Mckay, Hc Johnson, Jc Lloyd-jones, Sa Macgregor, Na Beattie, As WellerAbstract:A systematic study of catalyst structure and charge for the dehydroPolymerization of H3B•NMeH2 to form N-methylpolyaminoborane is reported using catalysts based upon neutral and cationic {Rh(Xantphos-R}} fragments, in which PR2 groups are selected from Et, iPr and tBu. The most efficient systems are based upon {Rh(Xantphos-iPr}}, i.e. [Rh(3–P,O,P–Xantphos–iPr)(H)2(2–H3B•NMe3)][BArF4], 6, and Rh(3–P,O,P–Xantphos–iPr)H, 11. While H2 evolution kinetics show both are fast catalysts (ToF ~ 1500 hr–1), and Polymer Growth kinetics for dehydroPolymerization suggest a classical chain Growth process for both, neu-tral 11 (Mn = 28,000 g mol–1, Ð = 1.9) promotes significantly higher degrees of Polymerization than cationic 6 (Mn = 9,000 g mol–1, Ð = 2.9). For 6 isotopic labelling studies suggest a rate determining NH activation, while speciation studies, coupled with DFT cal-culations, show the formation of a dimetalloborylene [{Rh(3–P,O,P–Xantphos–iPr)}2B]+ as the, likely dormant, end product of ca-talysis. A dual mechanism is proposed for dehydroPolymerization, in which neutral hydrides (formed by hydride transfer in cation-ic 6 to form a boronium co–product) are the active catalysts for dehydrogenation to form amino–borane. Contemporaneous chain–Growth Polymer propagation occurs on a separate metal center via head-to-tail end chain B–N bond formation of the aminoborane monomer, templated by an aminoborohydride–containing catalyst
