Inverse vulcanisation of self-activating amine and alkyne crosslinkers

Abstract

Inverse Vulcanisation is a versatile route to the synthesis of high sulfur content polymers. Developments to the field include expanding the variety of organic crosslinker molecules that can be used in the reaction, and the application of catalysis, which lowers the reaction time and the required temperature, as well as improving the yield and properties of the resultant polymers. However, concerns remain that the polymers may have a residual metal content from the catalysts, which is undesirable when considering environmental ramifications. There is also the question of whether the catalyst should be extracted from the polymer, which adds another processing step. Presented here is a study on crosslinkers that contain a non-metallic activating moiety built into their structure, thereby eliminating the aforementioned concerns whilst still providing several benefits. Also explored is the relatively untouched field of using alkynes, rather than alkenes, as crosslinkers, which have the potential to provide much higher crosslink densities in the resultant polymers, which may give favourable properties. The work presented here demonstrates the capability of the self-activating crosslinkers to be used as the sole crosslinker, where they can polymerise below the melting point of sulfur, or as a secondary crosslinker in another reaction, bringing the aforementioned benefits of catalysis.