Reaction Calorimetry for the Development of Ultrasound‐Induced Polymerization Processes in CO 2 ‐Expanded Fluids

A strong viscosity increase upon polymerization hinders radical formation during an ultrasound‐induced bulk polymerization. Since CO 2 acts as a strong anti‐solvent for most polymers, it can be used to reduce the viscosity of the reaction mixture. In this work, a process for the ultrasound‐induced polymerization in CO 2 ‐expanded fluids has been developed. Temperature oscillation calorimetry has been applied to study the influence of CO 2 on the viscosity during the ultrasound‐induced polymerization. In contrast to polymerizations in bulk, the results show that a low viscosity is maintained during polymerization reactions in CO 2 ‐expanded methyl methacrylate (MMA). As a consequence, a constant or even increasing polymerization rate is observed when pressurized CO 2 is applied. Moreover, the ultrasound‐induced polymer scission in CO 2 ‐expanded MMA is demonstrated, which appears to be a highly controlled process. Finally, a preliminary sustainable process design is presented for the production of 10 kg/hour pure PMMA (specialty product) in CO 2 ‐expanded MMA by ultrasound‐induced initiation.