Sustainable Polymers: Our Evolving Understanding

ConspectusThis 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.