Investigating the Role and Scope of Catalysts in Inverse Vulcanization

Abstract

Inverse vulcanization is a potential route to the use of the large excesses of elemental sulfur, creating high-sulfur-content polymers with many potential applications. The addition of a metal diethyldithiocarbamate catalyst was previously found to bring several benefits to inverse vulcanization, making the process more attractive industrially. Herein is reported the establishment and exploration of a library of catalysts for inverse vulcanization. Three ranges of catalysts and up to 32 compounds and their combinations have been investigated. By trialing these alternative catalysts, several tentative deductions about the mechanism have been made. It has been found that stronger nucleophiles give a greater rate enhancement, but with the tradeoff that harder bases may promote hydrogen sulfide byproduct formation. Monomer binding by the cation may be a crucial mechanistic step, and it is possible that the catalysts act as phase transfer agents between the immiscible sulfur and organic phases. Additionally, the versatility of catalytic inverse vulcanization has been demonstrated with several different comonomer families.

High strength composites from low-value animal coproducts and industrial waste sulfur

“…Most HSMs have been prepared by inverse vulcanization (Scheme 1), [1][2][3][4][5][6] although a few alternate methods for their synthesis and processing involving alternate chemical pathways have recently emerged as well. 36,[39][40][41][42][43][44][45][46] Inverse vulcanization relies on the reaction of olens with thermally generated sulfur radicals. A wide range of olens serve as viable comonomers in inverse vulcanization, including numerous bio-derived examples such as limonene, modied cellulose or lignin, nely ground peanut shells, and plant-derived terpenoid alcohols like citronellol, geraniol and farnesol.…”

On the Fundamental Polymer Chemistry of Inverse Vulcanization for Statistical and Segmented Copolymers from Elemental Sulfur

“…Furthermore, inverse vulcanized polymers are primarily amorphous materials, or polymeric fluids with glass transitions typically below 50 °C as increasing sulfur content tends to lower the glass transition and thermomechanical properties of these materials, although a few notable organic comonomers have been observed to afford sulfur copolymers possessing T g 's exceeding 100 °C. [9] While advances in the scope of monomers, nucleophilic and transition metal accelerators for inverse vulcanization have proceeded, [24,[29][30][31] there remains a need to expand the synthetic variations and polymerization transformations with inverse vulcanization to prepare enhanced polymeric materials from S 8 . These types of synthetic advances are challenging since the majority of single step inverse vulcanization processes tend to afford amorphous polymeric materials, which complicates the preparation of segmented block copolymers, or semi-crystalline (co)polymers as a route to enhance thermomechanical properties.…”

Modelling mercury sorption of a polysulfide coating made from sulfur and limonene

“…28 Recently, it was discovered by Hasell and co-workers that the same material could be made at a lower temperature and with fewer byproducts through the use of an accelerator or catalyst such as zinc diethyldithiocarbamate. 29,30 This advance eliminated the need for the distillation step, as less limonene is oxidised to cymene and fewer thiols are formed.…”