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Real‐time monitoring by proton relaxometry of radical polymerization reactions of acrylamide in aqueous solution
Author(s) -
Rodrigues Elton Jorge da Rocha,
Neto Roberto Pinto Cucinelli,
Sebastião Pedro José Oliveira,
Tavares Maria Inês Bruno
Publication year - 2018
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/pi.5546
Subject(s) - polymerization , radical polymerization , relaxometry , aqueous solution , chemistry , monomer , solution polymerization , relaxation (psychology) , reaction rate constant , bulk polymerization , materials science , photochemistry , kinetics , polymer chemistry , polymer , organic chemistry , spin echo , medicine , psychology , social psychology , physics , quantum mechanics , magnetic resonance imaging , radiology
Abstract The potential of time‐domain nuclear magnetic resonance (TD‐NMR) for the real‐time monitoring of solution radical polymerizations is demonstrated. A model system composed of a redox‐pair initiator system, acrylamide as monomer and water as solvent was investigated. A second‐generation continuous wave free precession technique was employed to measure the longitudinal relaxation time constant ( T 1 ) of the samples throughout the polymerization reactions. This parameter was shown to be sensitive to the reactant feed free‐radical enhancement of the water molecule relaxation time, making it a good probe to monitor monomer conversion in real time in an automated, non‐destructive fashion. It was found that the T 1 value was better than the transverse relaxation time constant ( T 2 ) for describing the evolution of the polymerization reactions, due to its greater sensitivity to paramagnetic effects. The TD‐NMR signal variation observed was linked to the formation, propagation and termination steps of the radical polymerization kinetics scheme. These first results may contribute to the application of real‐time monitoring of radical polymerization reactions employing low‐cost and robust TD‐NMR spectrometers. © 2018 Society of Chemical Industry