The mission of the NSF Center for Sustainable Polymers (CSP) is to transform how plastics are made, unmade, and remade through innovative research, engaging education, and diverse partnerships that together foster environmental stewardship. Center researchers pursue basic polymer science research aimed at developing new, practical chemistries, polymers, processes, and technologies that embrace sustainability and promote future economic development.

Each of the center’s three Grand Challenge Project Areas (GCPAs) was selected for its ability to advance the basic fundamental research necessary to make sustainable polymers an eventual reality for consumers. Significant progress was made in each area by relying on the expertise of the investigators involved in the center as well as leveraging the structure of the center to foster collaboration and accelerate research progress. Highlights of these efforts are summarized below.

In GCPA I, Efficient and Sustainable Conversion of Biomass to Polymer Ingredients, researchers designed bacterial processes to produce high value chemicals from biomass via metabolic engineering routes. These processes were used to make degradable biobased elastomers, and were also found to be useful in high-performance polyurethane foams that were chemically recyclable. A startup company was formed to commercialize these new materials. Additionally, center researchers developed a hybrid bioengineering/heterogeneous catalysis process to obtain isoprene from sugar in high yield. This process may be an alternative route to isoprene, used in synthetic rubber for tires.   

In GCPA2, High-Performance Sustainable Plastics, Elastomers, and Thermosets, CSP researchers discovered new crosslinked polyhydroxyurethane thermosets with competitive mechanical properties. These systems also avoid the use of toxic isocyanate monomers typical in polyurethane synthesis. Unfortunately, commodity thermosets are non-repairable and are discarded or destroyed after failure, making them unsustainable. Developing recyclable or reprocessable materials with similar properties to thermosets, under service conditions, is a major challenge.

Additionally, researchers in the center cross-linked betacyclodextrin (β-CD) with tetrafluoroterephthalonitrile (TFN), providing the first mesoporous, high surface area β-CD polymer. This polymer removes organic contaminants with unprecedented speed and high capacity (i.e. only a few seconds). For example, bisphenol A (BPA) is removed more rapidly than contemporary sorbents, including a high-end activated carbon filter. A second polymer variant showed outstanding removal of perfluorinated alkyl substances (PFAS). PFAS pollutants are estimated to impact 50 million Americans. Three patents are associated with these discoveries, and a startup company was launched to commercialize these materials.

In GCPA3, Sustainable Polymer Degradation, Chemical Recycling, and Compatibilization researchers developed new, high-performance crosslinked materials with more sustainable characteristics. Aliphatic polyesters can be synthesized from biomass, and the ester bonds in the polymer backbone enable degradation on reasonable timescales. Through collaboration with ETH Zürich researchers studied the enzymatic hydrolysis of the elastomers, a process that is key for their biodegradation (i.e., by microorganisms). The elastomers were quite susceptible to enzymatic cleavage, which bodes well for them to have minimal environmental impact. This holistic investigation into the preparation, characterization, and biodegradation potential of the polyester elastomers would not have been possible without the collaborative environment provided by the CSP.

Polyethylene (PE) and isotactic polypropylene (iPP) are the two most abundant plastics worldwide and account for about two-thirds of all plastic production. Despite their similar hydrocarbon composition, these polymers phase-separate, which erodes the mechanical properties of melt blends and creates challenges for recycling. Given the abundance, utility, and environmental impact of PE and iPP, there is a compelling need to improve the recyclability and associated mechanical properties of these repurposed materials. A CSP research team discovered that as little as 1 wt% of a newly created PE/iPP multiblock polymer could compatibilize commercial PE and iPP into remarkably tough composite blends.

In addition to this selected list of scientific accomplishments the CSP has had significant successes in the integrative elements as well. 23 patents were submitted during this reporting period in addition to the two startup companies noted above. Several undergraduate and high school level laboratory courses in sustainable polymer and green chemistry were developed and published, and an extensive multi-year partnership with 4-H and SciGirls has resulted in sustainable polymer focused curriculum modules for grade bands aged K-2, 3-5, and 6-8 for use in the informal environment. These modules have also resulted in a licensing agreement with National 4-H for dissemination through their site, the 4-H Shop. Finally, the center has taken the professional development of our graduate students and postdoctoral researchers seriously and has offered numerous opportunities for their learning and growth. The CSP is committed to promoting and supporting diversity in all of its forms. Collaborations formed among people with varied views, perspectives, and backgrounds enhance the experiences of center participants and also form the foundation for creative and innovative solutions to grand challenges in the field. The CSP embraces an atmosphere of mutual respect that is free from prejudice and intolerance and works to increase the engagement of individuals from groups underrepresented in the STEM fields.

Last Modified: 11/19/2020
Modified by: Marc A Hillmyer