Inverse vulcanization

As a result, the liquid sulfur is constituted by linear polysulfide chains with diradical ends, which can be easily bridged together with small dienes, such as 1,3-Diisopropylbenzene(DIB),[1] 1,4-diphenylbutadiyne,[2] limonene,[3] divinylbenzene (DVB),[4] dicyclopentadiene,[5] styrene,[6] 4-vinylpyridine,[7] cycloalkene[8] and ethylidene norbornene,[9] or longer organic molecules as polybenzoxazines,[10] squalene[11] and triglyceride.

As a consequence, sulfur-rich materials made via inverse vulcanization are characterized by a high refractive index (n~1.8), whose value depends again upon the composition and crosslinking species.

[15] As shown by thermogravimetric analysis (TGA), the copolymer thermal stability increases with the amount of added crosslinker; however, all the tested compositions degrade above 222 °C.

[17] The sulfur-rich copolymers made via inverse vulcanization could in principle find diverse applications due to their simple synthesis process and thermoplasticity.

In order to overcome the disadvantages related to the materials' low electrical conductivity (1015–1016 Ω·cm),[16] researchers have started to add special carbon-based particles to increase electron transport inside the copolymer.

Pure sulfur cannot be employed to manufacture a functional filter because of its low mechanical properties; therefore, inverse vulcanization was investigated to produce porous materials, in particular for the mercury capturing process.

[3][24][25] Sulfur-rich copolymers, made via inverse vulcanization, have advantages over traditional IR optical materials due to the simple manufacturing process, low cost reagents, and high refractive index.

As mentioned before, the latter depends upon the S-S bonds concentration, leading to the ability to tune the optical properties of the material by modifying the chemical formulation.