CAREER: Peptide-based plastics with customizable properties

Non-technical summary.

Plastics are indispensable materials in modern society because they are lightweight, cheap, flexible, and durable. These properties make plastics useful in daily consumer applications (such as in packaging materials) as well as in high performance applications (such as adhesives, electronics, or even body armor). However, we currently rely on a small set of chemical building blocks to create most plastics, which makes it difficult to repurpose one type of plastic for other applications and to safely and easily degrade plastics at their end of life.

A new set of chemical building blocks will be used—based on naturally occurring biological molecules—to create degradable plastics with custom properties. A new method is being developed to link together short biomolecules into long polymer chains (which are the general building blocks of plastics). By using a small set of biomolecules but arranging them along the chain in different sequences, it is expected that plastics with a wide range of properties (and thus, applications) can be created.

It is also hypothesized that the biomolecule arrangement will control how rapidly the plastics break down in water or soil conditions, thereby leading to plastics that can be safely degraded in the environment. Success of this proposed research may lead to a new class of plastics that are created from renewable resources, degraded safely in the environment, having tailored properties to suit a wide range of applications.

Technical summary.

Sequence-specific polymers are ubiquitous in biology, and synthetic analogues have shown promise as building blocks for materials with highly tunable properties. However, current approaches to synthesize sequence-specific polymers generally suffer from some combination of low efficiencies and yields, high cost, and an inability to generate polymer chains with high enough molecular weights to create free-standing materials.

Here it is proposed to use modular short peptides as “macromonomers,” allowing one to synthesize sequence-specific polymers with high molecular weights in a scalable manner via traditional chemical polymerization approaches. Specifically, native di- or tri-peptide molecules will first be coupled together to create a macromonomer that terminates at both ends in the same functional group and thus can be subsequently polymerized into high molecular weight chains using step growth polymerizations.

This approach should lead to polymer chains with sufficiently high molecular weights to create free-standing materials and whose sequence and composition are programmed via the initial di- or tri-peptide selection. Based on this sequence specificity and chemical diversity, it is hypothesized that peptide-based plastics can be fabricated with a wide range of tunable structures and bulk properties, analogous to how a biopolymer’s sequence dictates the structure and function of biological molecules and materials.

Further, it is hypothesized that the plastics can be degraded in eco-friendly conditions (by enzymes or microbes) in a manner that also depends on the polymers’ sequence. Success of the proposed work may lead to a new class of peptide-based plastics with customizable properties that can be synthesized in a scalable manner.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.