Synthesis of Poly(phenylene polysulfide) Networks from Elemental Sulfur and p-Diiodobenzene for Stretchable, Healable, and Reprocessable Infrared Optical Applications

Abstract

The synthesis and characterization of poly­(phenylene polysulfide) networks (PSNs) with controlled average sulfur ranks, from elemental sulfur (ES) and p-diiodobenzene (DIB), are investigated. The PSN films, prepared via simple hot pressing, are found to possess large extensibility up to around 300% and complete recovery of shape and mechanical properties after deformation, which are attributed to the loosely cross-linked network structures mainly consisting of linear poly­(phenylene polysulfide) chains. The covalent polysulfide linkages in the PSNs also exhibit dynamic behaviors under ultraviolet (UV) or thermal treatment, thus, enabling self-healing and reprocessing of the films when scratched and broken, respectively. Combined with the unique mechanical properties of the PSNs, their high refractive index and excellent infrared (IR) transparency contribute to the preparation of stretchable, healable, and reprocessable IR transmitting materials for potential deformable and stretchable optical applications.

Sequential crosslinking for mechanical property development in high sulfur content composites

“…Although a large body of the literature exists on HSMs prepared by InV, [1][2][3] only a few studies have been reported employing the RASP approach, by Lee et al [6] and Karunarathna et al [4,5] The regiochemistry and extent to which polymeric sulfur domains are attached to the aryl rings through direct S C aryl bond formation in the conversion of I-BPA 80 to R-BPA 80 was thus examined in more detail. First, a control reaction of elemental sulfur with Br 4 BPA, a model compound for M1 that lacks the InV-reactive olefin groups, gave clean conversion to thiol 2 in which the S C aryl bonds formed with the regiochemistry proposed in Scheme 2 for R-BPA 80 (Scheme 3a).…”

“…High sulfur-content materials (HSMs) can be conveniently prepared by the reaction of elemental sulfur with olefins by inverse vulcanization (InV) [1][2][3] or from aryl halides by radical-induced aryl halide-sulfur polymerization (RASP, Scheme 1). [4][5][6] HSMs produced by these routes have been proposed for applications such as electrode materials, [7][8][9][10][11][12] lenses for thermal imaging, [13] fertilizers [14,15] absorbents for removing toxins from water, [16][17][18][19][20][21] or as structural materials [22][23][24][25][26][27][28][29] and thermal insulators. [30,31] The InV mechanism proceeds when olefins are crosslinked by their reaction with sulfur radicals produced by heating elemental sulfur to >159 C. RASP involves thermal reaction of aryl halides with elemental sulfur whereby S C aryl bonds are formed, a process requiring slightly higher temperatures of 220-250 C.…”

“…[32][33][34][35] Polymeric sulfur domains can reform following their rearrangement by metathesis when the material is cooled back to room temperature, provided that the supporting network is intact , allowing materials to be reshaped or thermally healed. [6,22,26,[36][37][38][39][40] Two types of S S bonds are typically present in these materials: those in polymeric/oligomeric catenates that undergo metathesis at temperatures as low as 90 C and those in cyclic S 8 allotropes that generally require heating to above 159 C to undergo metathesis. In the absence of other species, the polymeric sulfur radicals are stable up until around 250 C, when a color change from red to black is noted.…”

“…Several studies have confirmed this hypothesis up to temperatures of up to 240 C, provided that the reaction is carried out in a sealed system to prevent physical escape of the sulfur monomer through sublimation. [4][5][6] In the current work, we sought to exploit the different temperatures required for InV and RASP as a way to facilitate sequential crosslinking of an appropriately derivatized organic monomer. Specifically, it was hypothesized that an olefin-derivatized aryl halide monomer could undergo InV at 180 C to facilitate S C olefin crosslinking, followed by RASP at higher temperatures (220 C) to increase crosslink density through S C aryl bond formation (Scheme 2 and Figure 1).…”

Scalable High Refractive Index polystyrene-sulfur nanocomposites via in situ inverse vulcanization

“…More recently, Kleine, et al, developed chalcogenide hybrid inorganic/organic polymers with enhanced long-wave infrared (LWIR) spectrum (7-14 µm), this low organic content terpolymers showed superior IR transparence and demonstrated the ability to take highly resolved thermal images in near or complete dark environment 32,33 . Similar chemistry of introducing S-S bond in the copolymer to improve the refractive index was later adopted by many researchers are prepared various HRI copolymers [34][35][36][37][38] .…”