NMR and EPR Structural Analysis and Stability Study of Inverse Vulcanized Sulfur Copolymers.

ABSTRACT: Sulfur copolymers with high sulfur content find a broad range of applications from Li-S batteries to catalytic processes, self-healing materials, and the synthesis of nanoparticles. Synthesis of sulfur-containing polymers via the inverse vulcanization technique gained a lot of attention due to the feasibility of the reaction to produce copolymers with high sulfur content (up to 90 wt %). However, the interplay between the cross-linker and the structure of the copolymers has not yet been fully explored. In the present work, the effect of the amount of 1,3-diisopropenyl benzene (DIB) cross-linker on the structural stability of the copolymer was thoroughly investigated. Combining X-ray diffraction and differential scanning calorimetry, we demonstrated the partial depolymerization of sulfur in the copolymer containing low amount of cross-linker (<30 wt % DIB). On the other hand, by applying NMR and electron paramagnetic resonance techniques, we have shown that increasing the cross-linker content above 50 wt % leads to the formation of radicals, which may severely degrade the structural stability of the copolymer. Thus, an optimum amount of cross-linker is essential to obtain a stable copolymer. Moreover, we were able to detect the release of H₂S gas during the cross-linking reaction as predicted based on the abstraction of hydrogen by the sulfur radicals and therefore we emphasize the need to take appropriate precautions while implementing the inverse vulcanization reaction.

SUBMITTER: Shankarayya Wadi VK 

PROVIDER: S-EPMC6641320 | biostudies-literature | 2018 Mar

REPOSITORIES: biostudies-literature