Sustainable Polymers: Our Evolving Understanding

This Account discusses the evolution of our strategy to conduct environmentally responsible research in the field of polymer chemistry. To contextualize our work, we begin with a broad historical overview of the modern environmental movement, the rise of sustainability as a concept, and how chemistry has responded to these forces, which were often sharply critical of our field. We then trace our own responses, from graduate school onward, chronicling a series of experiences and research projects that molded, challenged, and reshaped how we think about sustainability in polymer science.Since beginning our independent careers in 2004, we have recognized and worked to resolve the tension between designing synthetic polymers for specific desired thermomechanical properties and minimizing environmental impact. In our early years, we were most strongly guided by the 12 Principles of Green Chemistry (12PGC), which had only recently been proposed. The authors' early research agendas had a rather narrow focus on two areas, specifically catalysis and biobased monomers, which we saw as strongly linked to sustainability. Over time, we found these areas to be too narrow in their focus, ignoring important considerations such as the capacity of monomer supply to support scale-up and the impact polymers have at the end of their usage lifetimes. With respect to monomers and catalysts, we consider descriptive metrics that quantify waste production and the toxicity of compounds used during synthesis. In terms of polymer end-of-life, we discuss hydrophobicity as a tool to help understand susceptibility to degradation in the environment as well as some of the concerns with design for degradation, a critical component of 12PGC.Now, after nearly two decades of investigation, we believe that achieving sustainability in polymer science will require us to move beyond the qualitative use of the 12PGC to a portfolio of metrics. We note a heartening increase in the availability and use of such metrics and tools across the field. These include items that provide limited insight but are relatively trivial to integrate into existing workflows such as E factor or the Toxicity Estimation Software Tool. We also appreciate the increased use of Life Cycle Assessment (LCA), which is both dramatically more thorough and difficult to deploy. Finally, we propose the creation of a national LCA center, similar to instrumental core facilities. Such a resource would enable the use of this tool across multiple phases of research and we hope would more effectively guide us to a sustainable future.