Cationic degradation of poly(propylene sulfide)

Abstract

AbstractIntroduction of small amounts of sulfonium ions in poly(thiopropylene) (poly(propylene sulfide)) by means of triethyloxonium tetrafluoroborate was found to result in a rapid degradation reaction, first leading to low molecular weight polymers and ultimately to a mixture of low molecular weight cyclic products and propene. The reaction mixtures were analyzed by gas liquid chromatography, mass spectroscopy and, when the compounds could be isolated in sufficient amounts, by 1H NMR spectroscopy. The composition of the end product mixture was shown to depend on the concentration of sulfonium ions introduced at the beginning. With low initiator concentrations (≈ 10−3 mol.l−1) the main degradation product was found to be cyclic tetramer accompanied by decreasing amounts of cyclic pentamer, hexamer etc., and with high initiator concentrations (> 10−2 mol.l−1) the main degradation products are a mixture of dimethyl‐1,2,5‐trithiepanes and propene.