First steps in radiation-induced hydrogel synthesis

Radical formation and oligomerization in dilute aqueous N-isopropylacrylamide solutions

Ágnes Sáfrány, L. Wojnárovits

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

The reactions of hydroxyl radical, hydrogen atom and hydrated electron intermediates of water radiolysis with N-isopropylacrylamide (NIPAAm) were studied by pulse radiolysis in dilute aqueous solutions. OH, H and eaq- react with NIPAAm with rate coefficient of (6.9±1.2)×109, (6.6±1)×109, and (1.0±0.2)×1010mol-1dm3s -1. In OH and H radical addition to the double bond mainly α-carboxyalkyl type radicals form, (OHCH2CH·C(N-i-C3H7)O and CH3CH·C(N-i-C3H7)O). In reaction of eaq- oxygen atom centered radical anion is produced (CH2CHC·(N-i-C3H7)O -), the anion undergoes reversible protonation with pKa=8.7. There is also an irreversible protonation on the β-carbon atom that produces the same radical as forms in H atom reaction (CH3CH·C(N-i-C3H7)O). The α-carboxyalkyl type radicals at low NIPAAm concentration (0.1-1mmoldm-3) mainly disappear in self-termination reactions, 2kt,m=8.4×108mol-1dm3s -1. At higher concentrations the decay curves reflect the competition of the self-termination and radical addition to monomer (propagation). The termination rate coefficient of oligomer radicals containing a few monomer units is 2kt≃2×108mol-1dm3s 1.

Original languageEnglish
Pages (from-to)707-715
Number of pages9
JournalRadiation Physics and Chemistry
Volume67
Issue number6
DOIs
Publication statusPublished - Aug 1 2003

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radiation
synthesis
radiolysis
monomers
anions
hydroxyl radicals
coefficients
oligomers
atoms
oxygen atoms
hydrogen atoms
aqueous solutions
propagation
carbon
decay
curves
pulses
water
electrons

ASJC Scopus subject areas

  • Radiation

Cite this

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title = "First steps in radiation-induced hydrogel synthesis: Radical formation and oligomerization in dilute aqueous N-isopropylacrylamide solutions",
abstract = "The reactions of hydroxyl radical, hydrogen atom and hydrated electron intermediates of water radiolysis with N-isopropylacrylamide (NIPAAm) were studied by pulse radiolysis in dilute aqueous solutions. OH, H and eaq- react with NIPAAm with rate coefficient of (6.9±1.2)×109, (6.6±1)×109, and (1.0±0.2)×1010mol-1dm3s -1. In OH and H radical addition to the double bond mainly α-carboxyalkyl type radicals form, (OHCH2CH·C(N-i-C3H7)O and CH3CH·C(N-i-C3H7)O). In reaction of eaq- oxygen atom centered radical anion is produced (CH2CHC·(N-i-C3H7)O -), the anion undergoes reversible protonation with pKa=8.7. There is also an irreversible protonation on the β-carbon atom that produces the same radical as forms in H atom reaction (CH3CH·C(N-i-C3H7)O). The α-carboxyalkyl type radicals at low NIPAAm concentration (0.1-1mmoldm-3) mainly disappear in self-termination reactions, 2kt,m=8.4×108mol-1dm3s -1. At higher concentrations the decay curves reflect the competition of the self-termination and radical addition to monomer (propagation). The termination rate coefficient of oligomer radicals containing a few monomer units is 2kt≃2×108mol-1dm3s 1.",
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AU - Wojnárovits, L.

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N2 - The reactions of hydroxyl radical, hydrogen atom and hydrated electron intermediates of water radiolysis with N-isopropylacrylamide (NIPAAm) were studied by pulse radiolysis in dilute aqueous solutions. OH, H and eaq- react with NIPAAm with rate coefficient of (6.9±1.2)×109, (6.6±1)×109, and (1.0±0.2)×1010mol-1dm3s -1. In OH and H radical addition to the double bond mainly α-carboxyalkyl type radicals form, (OHCH2CH·C(N-i-C3H7)O and CH3CH·C(N-i-C3H7)O). In reaction of eaq- oxygen atom centered radical anion is produced (CH2CHC·(N-i-C3H7)O -), the anion undergoes reversible protonation with pKa=8.7. There is also an irreversible protonation on the β-carbon atom that produces the same radical as forms in H atom reaction (CH3CH·C(N-i-C3H7)O). The α-carboxyalkyl type radicals at low NIPAAm concentration (0.1-1mmoldm-3) mainly disappear in self-termination reactions, 2kt,m=8.4×108mol-1dm3s -1. At higher concentrations the decay curves reflect the competition of the self-termination and radical addition to monomer (propagation). The termination rate coefficient of oligomer radicals containing a few monomer units is 2kt≃2×108mol-1dm3s 1.

AB - The reactions of hydroxyl radical, hydrogen atom and hydrated electron intermediates of water radiolysis with N-isopropylacrylamide (NIPAAm) were studied by pulse radiolysis in dilute aqueous solutions. OH, H and eaq- react with NIPAAm with rate coefficient of (6.9±1.2)×109, (6.6±1)×109, and (1.0±0.2)×1010mol-1dm3s -1. In OH and H radical addition to the double bond mainly α-carboxyalkyl type radicals form, (OHCH2CH·C(N-i-C3H7)O and CH3CH·C(N-i-C3H7)O). In reaction of eaq- oxygen atom centered radical anion is produced (CH2CHC·(N-i-C3H7)O -), the anion undergoes reversible protonation with pKa=8.7. There is also an irreversible protonation on the β-carbon atom that produces the same radical as forms in H atom reaction (CH3CH·C(N-i-C3H7)O). The α-carboxyalkyl type radicals at low NIPAAm concentration (0.1-1mmoldm-3) mainly disappear in self-termination reactions, 2kt,m=8.4×108mol-1dm3s -1. At higher concentrations the decay curves reflect the competition of the self-termination and radical addition to monomer (propagation). The termination rate coefficient of oligomer radicals containing a few monomer units is 2kt≃2×108mol-1dm3s 1.

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