(Proc. CNPq 446323/2024-1)
Today, polymers are industrially produced through classical polymerization routes developed throughout the 20th century. Although these methods are effective at producing plastics from petroleum‑based monomers quickly and cheaply, they fail to generate materials that can be effectively recycled.
The main reasons preventing these materials from being reintroduced into production and consumption chains are:
Lack of control over macromolecular architecture and molar mass, which can accelerate degradation and loss of properties during thermo‑mechanical recycling.
Chemically crosslinked structures in many polymers, which make this type of recycling unfeasible.
At the same time, these characteristics hinder chemical recycling via depolymerization, which aims to recover the monomers used to produce new—or the same—polymers (with properties identical to the originals). This difficulty arises from the presence of diverse functional groups, branching and/or chemical crosslinking (originating from the uncontrolled polymerization processes currently used), as well as the challenge of breaking C–C covalent bonds, which form the backbone of most commercial polymers, especially polyolefins.
As a result, most polymeric materials produced today are single‑use, being discarded or incinerated after use due to the impossibility of recycling them—causing severe negative environmental impact.
The CIRCLE project proposes a unique, previously unexplored strategy aimed at:
enabling the production of polymeric materials that can be effectively recycled through chemical depolymerization;
facilitating the combination of polymers with renewable fillers, such as cellulose fibers; and
improving the properties of polymeric materials so they become more durable, minimizing disposal.
The project focuses on developing controlled polymerization routes for step‑growth polymers (SGPs), which contain C–X bonds—where X is a heteroatom other than hydrogen or carbon—in their main chain. This characteristic, combined with the strategic insertion of dynamic covalent bonds into the chemical structure of these controlled polymers (SGP‑dyn), promises to revolutionize the fields of polymer synthesis and chemical recycling.
SGPs are well known for their higher recyclability potential due to the greater lability of C–X bonds compared to C–C bonds, as well as their versatility in chemical structure—and therefore in properties and applications. Additionally, controlled polymerization routes will enable the insertion of dynamic covalent bonds at strategic positions along the polymer chain. Thanks to the higher lability and reversibility of these bonds, the energy efficiency of chemical recycling for SGP‑dyn will be unparalleled, allowing the recovery of precursors that can be reused to produce the same polymers.
Dynamic bonds will be inserted in positions that prevent the breaking of C–C bonds or other important functional groups during grinding—a crucial step in recycling. This will facilitate the production of oligomers with known terminal functionality, which can be easily separated from other depolymerization by‑products and reused to produce the same materials with identical performance.
To achieve these goals, the CIRCLE project will also investigate combining these controlled SGPs and SGP‑dyn with plant‑derived cellulose fibers to produce bio‑based composites (SGP‑dyn‑Cbio). The aim is to replace various polymers and their glass‑fiber and carbon‑fiber composites with fibers that actively capture and fix carbon during their production and use—unlike current synthetic fibers, which have a high carbon footprint.
Finally, the chemical recycling and life cycle of these (co)polymers and composites will be studied to demonstrate their sustainability and reduced environmental impact. Life‑cycle assessment (LCA) data will be used to support and train an artificial intelligence tool that predicts the environmental impact of new polymer synthesis and chemical recycling processes.
In the end, materials that combine the best mechanical performance, recyclability, and sustainability will be scaled up for production with the goal of commercialization.
The development of the CIRCLE project has strong potential to generate materials with superior mechanical performance compared to those currently used in many applications—while being easily recyclable, with minimal increases in cost or manufacturing complexity—addressing one of the most pressing problems faced by society today.
Control, Interface, Recycling, Catalysis, Life‑cycle, and Scaling
Central idea: Develop controlled step‑growth polymers (SGPs) and SGPs with dynamic covalent bonds (SGP‑dyn) to combine high performance, recyclability, and circularity.
Axes:
(i) Narrowing molar‑mass distribution (Đ < 1.5) and architectural control (blocks/topologies)
(ii) Integration of dynamic bonds for reprocessing and selective depolymerization
(iii) Bio‑based composites with cellulosic fibers
(iv) LCA + data to prioritize routes with better impact
(v) Scale‑up demonstrations
Impact: Replace conventional composites and polymers in advanced applications and enable efficient, sustainable chemical recycling.
LPF PROJECTS
learn more about this project
CARBON - Atmospheric CO₂ in Engineering Polymers
Research
Step‑Growth Polymerization
Sustainable and Circular Polymers
