Visible, Mid- and Long-Wave Infrared Transparent Sulfur-Rich Polymer with Enhanced Thermal Stability

Abstract

High sulfur content polymers (HSCPs) are regarded as promising materials for infrared (IR) optics, especially the long-wave IR range, due to intrinsic properties of sulfur, but the poor thermal stability of HSCPs limits their reliable utilization in wider IR applications. We herein present a new HSCP, poly­(sulfur-co-hexavinyl disiloxane) (pSHVDS), prepared directly from elemental sulfur through sulfur vapor chemical deposition (sCVD). By employing hexavinyl disiloxane (HVDS) comonomer with high functionality (f = 12) and weak absorption in the IR range, despite the poor compatibility between sulfur and HVDS, the sCVD process enables the preparation of highly cross-linked HSCP with 68 wt % sulfur. Furthermore, the combination of high refractive index (RI) of 1.842, high glass transition temperature (T g ) of 151 °C, and high transparency in visible, mid- and long-wave IR range is achieved successfully, which is an unprecedentedly unique property compared to HSCPs reported to date. These favorable properties of pSHVDS render the material ideal for antireflection applications in IR optics, and conformal pSHVDS coatings on germanium IR lenses significantly improved the transmittance in mid- and long-wave IR regions. The developed polymer will lead the new possibility for polymer based optical devices, especially in the IR range.

Diverse Side-Chain Transformation of High Refractive Index Methylthio-Substituted Poly(phenylene sulfide)s

“…The selective and partial oxidation of the side methylthio groups successfully enhanced near-UV–visible transparency without a serious increment in free volume. Therefore, this strategy can contribute to the precise modulation of the integrated performance (thermostability, RI, Abbe number, and transparency) of HRIPs-containing sulfur-rich side chains, breaking the empirical dichotomy ,, between these parameters.…”

“…The intermolecular H-bonds between thiols and the π−π interactions of PPS chains synergistically impeded the formation of long-range ordered structures, similar to the case of the hydroxy-substituted PPS. 16,17,27 In contrast to the general RI-T g dichotomy observed in various ultrahigh-RI polymer categories (e.g., high-sulfur content polymers), 24,35 this H-bonding approach can fulfill these parameters by reducing free volume.…”

“…Among the various SCPs, our focus has been on the poly­(phenylene sulfide) (PPS) family with side chains because of its high solubility, visible transparency, and high RI ( n D ∼ 1.7–1.8) resulting from a high aromatic and sulfur content . Notably, PPS with hydrogen bonds (H-bonds) , exhibits exceptional RI (above 1.8) along with significantly higher visible transparency and Abbe numbers (ν D ∼ 20) compared with other HRIPs, including poly­(thioamide)­s, , sulfur-rich polymers, , and sCVD-synthesized polymers. − Furthermore, PPS derivatives can undergo further functionalization via post-polymerization modification (PPM), enabling side chain and terminal transformations to enhance optical properties. ,, In particular, sulfide groups of PPS derivatives can also be oxidized to sulfoxide or sulfone, resulting in a higher valency of sulfur atoms and enhancing UV–vis transparency through the electron distribution tuning . However, employing such a main chain S = O introduction strategy may deteriorate the high RI properties of the original PPS derivatives owing to its high bulkiness (i.e., large molecular volume).…”

Structural Effect of Cyclic Olefin Cross-Linkers on Long-Wave Infrared-Transmitting Sulfur Polymers

“…High-sulfur content polymers are widely used in various applications including Li–S batteries, , heavy metal adsorption, − high refractive index ( n ) materials, − and infrared (IR) transmissive materials − thanks to the unique characteristics of the sulfur atom. In 2013, inverse vulcanization, a compelling process to prepare high sulfur content polymers using elemental sulfur and organic cross-linker, was established.…”

Value-Addition of Wastes from Petroleum Refining Process: Sulfur-Rich Polymers for Sustainable and High-Performance Optical and Energy Applications

“…From the perspective of recyclability, SRP can also be reused with negligible deterioration of mechanical and optical properties due to its self-healing property, originating from the dynamic bond exchange of the disulfide bond . During inverse vulcanization, we can employ various types of comonomers as shown in Figure d. ,− In the case of SRPs with sulfur weight content above 70 wt %, they typically exhibit a T g below 100 °C, excluding a few reports showing some limitations of thermal processability and mass productivity due to excessive cross-linking density and time-consuming vapor deposition process, respectively (Figure e). ,− …”