Electron spin resonance study of radical formation in cis-poly(phenylacetylene)/ferric acetylacetonate-triethylaluminum (PPA/Fe-Al). 2. Results and interpretation

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Title: Electron spin resonance study of radical formation in cis-poly(phenylacetylene)/ferric acetylacetonate-triethylaluminum (PPA/Fe-Al). 2. Results and interpretation
Author: Langner, Andreas; Ehrlich, Paul
Abstract: The line-shape and saturation analysis for inhomogeneously broadened ESR spectra, developed in the previous paper, is used to study the change of the PPA/Fe-Al resonance signal with temperature and polymer aging. A mechanism for radical formation, involving backbone cyclization reactions, is proposed to interpret the irreversible increase in spin concentration observed above -70 degrees C. As before, the spectra of the soluble and insoluble fractions of the polymer are interpreted as arising largely from triphenylcyclohexadienyl radicals formed upon cyclization of a cis-cisoid hexatriene precursor. An analysis of the resonance signal of the catalyst revealed that a low A1:Fe ratio at the active polymerization site leads to a high concentration of the cis-cisoid conformation. The presence of oxygen-complexed radicals with shorter spin-lattice relaxation times is inferred from saturation experiments.
Record URI: http://hdl.handle.net/1850/2194
Publishers URL: http://dx.doi.org/10.1021/ma00210a013
Date: 1990-04-19

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