An ESR study of the gamma radiolysis of aromatic polyesters containing isomeric naphthalene links

Six polyesters were synthesised from 4,4 ' -oxy-bis(benzoyl chloride) and 1 ,4-, 1,5-, 1,6-, 2,3-, 2,6-, and 2,7-naphthalenediol isomers. The structure s of the polyesters were characterised by means of IR, inherent viscosities in tetrachloroethane (TCE), solutions at 303 K and thermal analysis. The g lass transition temperatures were in the range of 425-494 K by DSC thermal analysis. All of the polyesters were irradiated in an AECL Gammacell 220 un it at a dose rate of approximately 6.7 kGy/h to doses in the range of 0-15 kGy at 77 and 300 K. ESR spectroscopy was used to examine the radicals form ed during radiolysis and to measure their yields. The G-values for radical formation in the polyesters were found to be in the range 0.18-1.41 at 77 K and 0.19-0.78 at 300 K. At 77 K, up to 15% of the radicals formed on radio lysis were found to be photo-bleachable anion radicals. Annealing experimen ts were carried out in order to identify the neutral radicals, which were a ssigned to naphthyl- or phenyl- and phenoxyl-type radicals. (C) 2001 Elsevi er Science Ltd. All rights reserved.