Thermal Imaging Using Sulfur Polymer Optics

Thermal imaging is used in security cameras, fire detection, driver assist features in automobiles, medical thermography and other safety applications. Unfortunately, lenses for thermal cameras are made from expensive or restricted materials such as germanium, silicon, or chalcogenide glass, which limits broader use. There is a need for low cost and sustainable alternatives. Sulfur-rich polymers, made from widely available elemental sulfur, are promising candidates due to their high refractive index and mid-wave infrared (MWIR, 3–5 um) and long-wave infrared (LWIR, 7–14 um) transmittance. However, much higher MWIR and LWIR transparencies are required to compete with industry standards. Recently, a copolymer containing a sulfurized norbornane core (1) was predicted by Pyun, based on theoretical considerations, to address this need. However, this polymer has not been made due to complex chemistry encountered in previously attempted syntheses. Here, we overcome these challenges and synthesize this polymer for the first time and validate its use in thermal imaging.