Thermal and photodegradation of polysulfide pre-polymers: products and pathways

Abstract

The thermal and photodegradation of a number of linear polysulfide (LP) pre-polymers H(SC 2H 4OCH 2OC 2H 4S) n H have been studied by 1H and 13C NMR spectroscopy, IR spectroscopy, gel permeation chromatography (GPC) and particularly, by electrospray ionisation mass spectrometry (ESI). ESI results point to the important role of hydrolytic pathways leading to the elimination of CH 2O and the formation of hydroxy-terminated products, followed by the reduction of disulfide groups by CH 2O. This conclusion is supported by the observation of very slow degradation by heat or UV-light of an LP containing no formal group. IR and NMR data show the formation of carbonyl-containing products by an oxidative free-radical pathway: 2D NMR data confirm that a formate ester is the main carbonyl-containing product, as authenticated recently in the degradation of various polyglycols.