The synthesis of polyepoxides from unsaturated polymers and their attempted isomerisation to polyketones

Abstract

Polybutadienes or polyisoprenes with >98%E-double bonds in the backbone can be epoxidised in quantitative yield to polyepoxides using Bu^tOOH in the presence of dichloro[(1R)-endo-(+)-3-(diethoxyphosphoryl)camphor]dioxomolybdenum(vi) and molecular sieves. The polymers formed can be isolated in a pure form provided that HCl, which otherwise promotes crosslinking, is removed from the reaction solution.

Attempts to isomerise the polyepoxides to polyketones using LiBr in the presence or absence of hexamethylphosphoramide (HMPA) or dimethylimidazolidinone (DMI) were partially successful, although the products generally tended to be insoluble as a result of aldol-type crosslinking reactions. For epoxides derived from polyisoprene, soluble isomerisation products can be obtained but these contain, in addition to ketone and unreacted epoxide units, ketals formed from reactions of isomerising epoxides with adjacent intact epoxide units.

The thermal properties of the polyepoxides are discussed.