Idriss Blakey - Energy Transfer and Activated Chemiluminescence during Thermal Oxidation of Polypropylene: Evidence for Chemically Induced Electron Exchange Luminescence.

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  Blakey, I.; George, G. A.; Billingham, N. C.,    Macromolecules 2001, 34 (26), 9130-9138.


  The mechanism of chemiluminescence (CL) during thermal oxidn. of   polypropylene (PP) was probed by doping PP with an energy   acceptor (9,10-dibromoanthracene [DBA]) and a chemiluminescence   (CL) activator (9,10-diphenylanthracene [DPA]). Doping PP with   DBA had little effect on the shape of the CL intensity (ICL)-time   profile. This suggests that energy transfer from triplet states   is probably not significant in the scheme of PP CL. However, the   CL activator (DPA) had a significant effect on the shape and   intensity of the ICL-time profile. In the absence of DPA, the   ICL-time profile matches the profile for the formation of   carbonyl-contg. oxidn. products from FTIR-emission spectra. In   contrast, in the presence of DPA, it was the integrated DPA   ICL-time profile which matched the oxidn. product profile,   indicating that now ICL was proportional to the hydroperoxide   concn. It is suggested that peroxides formed during PP oxidn. are   capable of reacting with DPA to produce chem. induced electron   exchange luminescence (CIEEL). It is also suggested that CL from   undoped PP, i.e., direct CL, may also occur by a CIEEL mechanism.   This mechanism is believed to involve the reaction of PP   peroxides with an easily oxidizable luminescent oxidn. product.   For the detector system used in this study the majority of light   emitted is consistent with reactions between acyl peroxides and   a,b-unsatd. carbonyls. The consequences of this mechanism are   that the ICL-time curve measured during the oxidn. of PP may   reflect either the hydroperoxide profile or the oxidn. product   profile depending on the spectral wavelength analyzed or the   state of purity of the polymer.

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