PolyNIMMO is regarded as an energetic polymer. It consists of a nitrated ester group and an ether linkage. When polyNIMMO is subjected gamma radiation up to doses of 250 kGy there is no evidence of degradation, however, at higher levels of gamma radiation up to 750 kGy structural changes in the polyNIMMO backbone were observed [Polymer 44 (2003) 7617-7624]. These observations were based on polyNIMMO which was gamma irradiated in the bulk phase [Polymer 44 (2003) 7617-7624; Polymer 42 (2001) 7711-7718]. The results presented in investigation are from polyNIMMO which has been irradiated in solution. PolyNIMMO dissolved in halogenated and aromatic solvents was found to undergo structural changes when subjected to doses of gamma radiation up to 250 kGy. An increase in molecular weight and glass transition temperature was observed with the formation of water and an aldehyde. End chain linking together with hydrogen abstraction of the pendant methyl group were the two suggested reaction schemes. (C) 2004 Elsevier Ltd. All rights reserved.