Correlated electron spin-resonance and infrared spectroscopic study of the postformation auto-oxidation phenomenon in plasma-polymerized 4-vinyl pyridine films

Autor: James C. Tou, Paul J. O'connor, Ahmed S. Ellaboudy
Rok vydání: 1996
Předmět:
Zdroj: Journal of Applied Polymer Science. 60:637-647
ISSN: 1097-4628
0021-8995
DOI: 10.1002/(sici)1097-4628(19960425)60:4<637::aid-app18>3.0.co;2-w
Popis: Plasma polymerization of 4-vinyl pyridine (4-VP) proceeds through a gas-phase free radical mechanism to yield a film that retains much of the organic functionality of the monomer. During the deposition process, free radicals, which have been shown to quickly react with oxygen, are trapped to yield a film with a nascent peroxy radical density of 2.9 × 1018 spins/gas quantified by electron spin resonance (ESR) spectroscopy. In air at room temperature, peroxy radicals in the film react to produce carbonyl, hydroxyl, and ether structures in the polymer that was monitored using infrared (IR) spectroscopy. The free radical population was found to decay rapidly at first and then reach an apparent steady state after 30 hr. As the spin density decreases, a concomitant growth of vibrational modes associated with oxygen-containing functional groups was observed in the IR spectrum of the film. The relative population of oxygen-containing groups continued to increase even after the free radical population reached steady state. This slow, auto-oxidative effect may be attributed, in part, to free radical centers that are anchored to the polymer chain in regions of high crosslinking. In such regions, limited segmental mobility may limit the rate of radical-radical recombination (termination) proceses relative to oxidative radical-center. © 1996 John Wiley & Sons, Inc.
Databáze: OpenAIRE
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