Processable Inverse-Vulcanized Polymers With Silicon-Like High Refractive Index and Transmittance for Infrared Optics

Polymers prepared by inverse vulcanization have demonstrated overwhelming superiority over traditional organic materials for application as infrared optical materials. It is however still a great challenge to achieve suitable refractive index (n) and infrared transparency for all-organic polymers, in contrast to inorganic optical materials. Herein, poly(S-TTF) polymers with controlled sulfur feeding ratio were constructed by inverse vulcanizing tetrathiafulvalene (TTF, a very sulfur-rich monomer). The resulting poly(S-TTF) possessed large polarizability, multiple reaction sites, and high symmetry that endow the polymers with increased infrared refraction and transmission. Together with remarkable stability, lightweight and good processability in imprint lithography, the poly(S60-TTF) with 88wt% sulfur content exhibits a competitive and tunable refractive index (∼3.0) and transmittances of >60% in near and mid-infrared regions by a millimeter-level optical window. An ideal transmittance of visible light (T_Vis < 2%) and near infrared (T_NIR > 90%) was also realized for poly(S60-TTF) films with 5µm thickness. Our strategy not only yields organic copolymers with competitive refractive index and exclusive infrared transmittance over inorganic materials for imaging and security applications, but also provides a valuable reference for balancing optical properties of inversed-vulcanized polymers using sulfur-ultrarich monomers.