Environmental Impact Differences of Single-Chain Nanoparticle Production by Batch and Flow Chemistry

Emerging nanoscale materials are under development for multiple high-performance product applications such as advanced polymers. Single-chain polymer nanoparticles (SCNPs) have many promising high-performance uses in catalysts, lubricants, nanoreactors, and biomedical applications; however, synthetic routes to SCNPs are still under development and usually require an excessive amount of solvent, imposing costly environmental impacts. Following our previous experimental study in which we developed a flow process for SCNP production and demonstrated its advantages in productivity and yield over classical batch preparation, in this study we apply prospective life cycle assessment (LCA) methods to evaluate alternative SCNP synthesis routes through a photochemistry process and examine the role of limiting solvent quantity and type used. We compare SCNP production through a flow photochemical process versus a classical batch process. Using a cradle-to-gate system boundary, we compare the performance of different batch and flow processing scenarios, considering solvent recovery through vacuum distillation, atmospheric distillation, and solvent replacement and waste solvent treatment. The results indicate that there are environmental benefits under the flow process over conventionally used batch processes where the solvent is recovered through atmospheric distillation, and toluene is the preferred solvent. In addition, we compare the LCA results to a common green chemistry metric known as the environmental factor and conclude that a green chemistry metric alone is insufficient. Hence, a comprehensive and systematic life cycle approach is needed to understand the environmental impacts of flow chemistry with potential scenarios prior to scaling up production.