Electron-beam initiated crosslinking in poly(N-isopropylacrylamide) aqueous solution |
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Affiliation: | 1. AMO GmbH, Otto-Blumenthal-Str. 25, 52074 Aachen, Germany;2. Laser-Laboratorium Göttingen e.V., Hans-Adolf-Krebs-Weg 1, 37077 Göttingen, Germany;1. College of Information Science and Engineering, Northeastern University, Shenyang 110004, China;2. Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, #08-03, Innovis, Singapore 138634, Singapore |
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Abstract: | The reactions between the OH, H and eaq− transients of water radiolysis and a linear poly(N-isopropylacrylamide) were identified by the spectral and kinetic properties of intermediates. The radical responsible for crosslink formation is the isopropyl-centered radical that forms mainly in OH radical attack on the polymer. Below pH 3 this radical undergoes reversible protonation with pKa≈2.1. The radical decay is composed of fast and slow parts. The initial fast decay is attributed to intramolecular reactions of radicals on the same chain (loop formation), the following slow decay to competition between further intramolecular and intermolecular (H-type crosslinks) termination processes. The differences in the network formation during irradiation of aqueous monomer and polymer solutions are discussed. |
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