Inverse vulcanization below the melting point of sulfur†
Elemental sulfur is an abundant by-product of the petrochemical industry, but polymers formed from pure sulfur cannot be used because they are not stable and depolymerize to the monomer, S8. Inverse vulcanization reported recently uses vinylic monomers as crosslinkers to stabilize polymers made from elemental sulfur. Here we report that the catalyst sodium diethyldithiocarbamate trihydrate allows inverse vulcanization to be conducted at low temperatures (110 °C), even below the melting point of sulfur (120 °C). Lower reaction temperatures are beneficial for not only energy economy, but also in preventing dangerous auto-acceleration and hydrogen sulfide generation, and allowing low boiling point monomers to be used. Excess catalyst can be recovered from the polymers, and despite a crosslinked structure, the reversibility of the S–S bonds allows the polymers to be recycled.