Consistent with the high LWIR transmittance of 67-poly(S-r-CPD), thermal imaging through a 1 mm thick window of the polymer was possible with an infrared camera operating in the 7.5-13 µm range. Notably, human subjects could clearly be imaged through the polymer window (Fig. ), which is only possible with high LWIR transmittance. In a new application for this class of material, a polymer sheet was made by hot-pressing the powdered polymer at 140 ºC and 30 MPa for 10 minutes , for subsequent use as a protective barrier that conceals thermal imaging equipment in low light (Fig. ). The 67-poly(S-r-CPD) absorbs visible light and appears black, which is distinct from other sulfur-based polymers for infrared imaging that are partially transparent to visible light and appear yellow, orange, or red . This unique property of 67poly(S-r-CPD) enables protection of the thermal imaging equipment from the environment and concealment of the camera (Fig. ). Such capabilities may find use in clandestine surveillance for wildlife monitoring, and defense and security applications. based materials. The featured polymer could also be converted into a sheet useful for the protection and concealment of thermal imaging equipment due to its unique absorption of visible light and transmission of LWIR light. Computational methods were also devised that provided insight into how the infrared spectrum of these sulfur copolymers is influenced by specific chemical and structural features. Such insights will help guide the design and synthesis of these materials to further improve their performance in thermal imaging. Future studies will expand on the reaction of volatile monomers with sulfur, clarify mechanistic steps of this copolymerization, and provide new materials for use in infrared optics.