Differential Scanning Calorimetry Sees the Light: Simultaneous Photo-Irradiation and Temperature Ramping of Sealed DSC Crucibles for Thermal Assessment of Photochemical Processes

Before scaling up a chemical reaction to industrial scale, it is essential to assess and mitigate any safety hazards including the potential for hazardous exotherms or thermal runaway. Sealed-crucible differential scanning calorimetry (sc-DSC) is an essential tool for thermal hazard analysis for both raw materials and reactions, but this technique is not well-suited to photochemical applications, as it traditionally requires opaque high-pressure metallic crucibles that do not allow for light penetration, making simultaneous temperature ramping and irradiation impossible. We report a novel technique involving a reusable DSC crucible with a transparent polymeric window that allows for irradiation of a sample during DSC temperature ramping experiments up to 250 °C while maintaining pressures of up to 25–36 bar depending on window diameter. This technique allows for the assessment of critical safety data such as decomposition onset temperatures in the presence of irradiation. The design and optimization of the crucible and film are discussed, and several proof-of-concept examples are reported, including sealed-crucible DSC analysis of photocuring of a polymeric resin, exothermic decomposition of dihalodimethylhydantoins and 2,4-dinitrobenzaldehyde, and photoisomerization of azobenzene derivatives.