35 research outputs found
Phthalate plasticizers covalently linked to PVC \u3ci\u3evia\u3c/i\u3e copper-free or copper catalyzed axide-alkyne cycloadditions
Plasticization of PVC was carried out by covalently linking phthalate derivatives via copper-free (thermal) or copper catalyzed azide-alkyne cycloadditions. Di(2-ethylhexyl) phthalate derivatives (DEHP-ether and DEHP-ester) were synthesized and appended to PVC at two different densities. The glass transition temperatures of the modified PVC decreased with increasing content of plasticizer. PVC-DEHP-ether gave lower glass transition temperatures than PVC-DEHP-ester, reflecting the enhanced flexibility of the ether versus ester linker
Internal plasticization of poly(vinyl) chloride using glutamic acid as a branched linker to incorporate four plasticizers per anchor point
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Relative Rates of Metal-Free Azide-Alkyne Cycloadditions: Tunability over 3 Orders of Magnitude.
The thermal (3 + 2) dipolar azide-alkyne cycloaddition, proceeding without copper or strained alkynes, is an underutilized ligation with potential applications in materials, bioorganic, and synthetic chemistry. Herein, we investigate the effects of alkyne substitution on the rate of this reaction, both experimentally and computationally. Electron-withdrawing groups accelerate the reaction, providing a range of relative rates from 1.0 to 2100 between the slowest and fastest alkynes studied. Unexpectedly, aryl groups conjugated to the alkyne significantly retard the reaction rate. In contrast, a sulfonyl, ester-substituted alkyne is reactive enough that it couples with an azide at room temperature in a few hours. This reactivity scale should provide a guide to those who wish to use this ligation under mild conditions
Synthesis of fluorinated alkoxyamines and alkoxyamine-initiated nitroxide-mediated precipitation polymerizations of styrene in supercritical carbon dioxide
TIPNO (2,2,5-trimethyl-4-phenyl-3-azahexane-3-nitroxide)-alkoxyamine was found to give reasonably controlled/living nitroxide-mediated (NMP) precipitation polymerizations of styrene in supercritical carbon dioxide (scCO(2)). In contrast under the same conditions, the analogous SG1 (N-tert-butyl-N-(1-diethylphosphono-2,2-dimethylpropyl)nitroxide)-alkoxyamine gave higher rates of polymerization and inferior controlled/living character. The circumvention of the requirement for excess free (nitroxide](0) allowed the study of nitroxide partitioning effects in scCO(2) for three newly synthesized fluorinated alkoxyamines. Two alkoxyamines dissociated into scCO(2)-philic fluorinated TIPNO-nitroxide derivatives, while another contains a similar sized fluorinated "foot". Despite the increased steric bulk about the N-O bond for the novel fluorinated alkoxyamines, all polymerizations proceeded at a similar rate and level of control to the TIPNO system in solution (toluene). PREDICI simulations for the styrene/TIPNO system are used to support extensive partitioning effects observed in scCO(2) for the fluorinated alkoxyamines.Irish Research Council (formerly IRCSET) IUPAC Transnational Call in Polymer Chemistry to F.Aldabbagh.
National Science Foundation (NSF CHE-1057927, USA) to R. Braslau.peer-reviewe
Advances in Internal Plasticization of PVC: Copper-Mediated Atom-Transfer Radical Polymerization from PVC Defect Sites To Form Acrylate Graft Copolymers
Radical Chemistry By M. J. Perkins (Brunel University, London). Ellis-Horwood: New York. 1994. x + 182 pp. $25.95. ISBN 0-13-320920-2.
Handbook of Radical Polymerization Edited by Krzysztof Matyjaszewski (Carnegie Mellon University) and Thomas P. Davis (University of New South Wales). John Wiley & Sons, Inc.: Hoboken. 2002. xvi + 920 pp. $200.00. ISBN 0-471-39274-X.
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Synthesis and spin trapping properties of polystyrene supported trifluoromethylated cyclic nitrones.
Polystyrene supported fluorinated cyclic nitrone spin-traps: Resin-2-HFDMPO (2-hydroxymethyl-2-methyl-5-(trifluoromethyl)-3,4-dihydro-2H-pyrrole-1-oxide) and Resin-2-PFDMPO (2-(3-hydroxypropyl)-2-methyl-5-(trifluoromethyl)-3,4-dihydro-2H-pyrrole 1-oxide) containing a trifluoromethyl pyrroline-N-oxide core were developed to detect free radicals under flow conditions. A continuous flow EPR technique was used to evaluate the spin trapping properties of these tethered nitrones. While both resins trapped radicals, polymer supported nitrone Resin-2-PFDMPO with a longer and more flexible linker showed a more information rich spectrum than Resin-2-HFDMPO