Novel Sulfur-Rich Polymers from Inverse Vulcanization as Functional Building Blocks for Photonics

Novel Inverse Vulcanized Polymers (IVPs) with high refractive index and excellent transparency in the NIR are achieved exploiting the recently emerged Inverse Vulcanization (IV) process as a simple, green, efficient, and scalable synthetic method to upcycle elemental Sulfur, which is accumulating in the environment as a by-product of the oil and gas industry. Co- and ter-polymers with Sulfur content 50 or 60 wt% are prepared in quantitative yields utilizing different crosslinking aromatic comonomers bearing isopropenyl functionalities. To the best of our knowledge, for the first time, two novel diisopropenyl aromatics, namely 2,7-diisopropenylfluorene (DIF) and 2,8-diisopropenyldibenzothiophene (DIDBT), are designed, prepared in very high yields via a sustainable, facile, single-step Suzuki-Miyaura cross-coupling reaction, and explored as suitable crosslinking comonomers for the IV reaction. Subsequently, comonomer(s) nature, number of their functionalities, as well as Sulfur-to-comonomer(s) ratio are varied to address both the optical behavior and filmability of the ensuing IVPs, which are technologically relevant properties for their application and industrial scale-up. Crosslink density is nicely correlated with the experimental glass transition temperatures of the investigated systems. Synthesized IVPs are then employed to fabricate all-polymer distributed Bragg reflectors (DBRs) and imprinted optical components. Results pave the way for diverse applications of IVPs in advanced nanophotonics.