The material is based on a class of sulfur-containing molecules known as 1,2-dithiolanes. The Surrey team’s study, published in Macromolecules, investigates polymers made from a specially designed lipoic-acid-derived building block, described in the paper as “lipoic acid without the side chain.” In polymer chemistry, small molecular units called monomers are joined through chemical reactions to create long chains. Those chains determine whether a material behaves like a soft film, a rigid solid, a rubber or a liquid. In this case, the monomer’s strained five-membered disulfide ring gives the polymer unusual chemical reversibility, allowing the long chains to break apart and reform under controlled conditions.

Most everyday plastics are valuable precisely because their molecular structures are difficult to disrupt. Polyethylene, used in carrier bags, food packaging and shampoo bottles, consists of stable carbon–carbon backbones that do not readily return to their original building blocks. Mechanical recycling can turn such plastics into lower-quality products, but chemical recycling is more demanding because the polymer must be broken down and the resulting compounds often require purification and further chemical processing. Even many polymers designed for chemical recycling need temperatures of approximately 150 to 200 degrees Celsius before depolymerisation becomes efficient. The Surrey material follows a different path, breaking down at about 90 degrees Celsius and producing a vapour rather than a liquid mixture of recovered monomers.

Depolymerisation is the reverse of polymerisation: instead of joining monomers into long molecular chains, it separates those chains back into their constituent units. When the Surrey polymer is heated, the bonds connecting the repeating 1,2-dithiolane-derived units can undergo a reversible ring-opening and ring-closing process. The polymer therefore loses its large-chain structure and converts into small molecules with sufficient volatility to enter the gas phase. As the vapour cools, the molecules condense and spontaneously polymerise, rebuilding the original material. This behaviour resembles sublimation and deposition more closely than conventional melt processing, because the polymer can move directly between a solid surface and a vapour without first passing through an ordinary liquid state.

That physical transformation could make the material particularly useful as a coating. To demonstrate the concept, the researchers generated a vapour from the polymer and allowed it to condense onto a surface, forming a continuous waterproof layer. Vapour deposition can reach areas that are difficult to cover with conventional liquid coatings, including intricate geometries, narrow gaps and textured surfaces. Liquid paints and protective films may pool, drain or leave uncovered regions when applied to complex objects. A vapour, by contrast, can travel across a surface before condensing, potentially producing a more uniform film. The resulting coating retained the soft, insoluble and hydrophobic characteristics associated with the polymer.

The same process can also remove the coating without solvents or aggressive chemical treatments. When the coated object is reheated to around 90 degrees Celsius, the polymer evaporates from the surface and can, in principle, be captured for reuse. This reversibility could be valuable in manufacturing, electronics, laboratory equipment and other applications where a temporary waterproof or protective layer is needed. A coating might be applied during fabrication, removed during repair, or recovered when a product reaches the end of its useful life. The approach could reduce the need for solvent-based stripping, although the researchers emphasise that practical systems would still need to address energy use, vapour containment, coating thickness and large-scale recovery.

The team also tested whether the polymer could be purified through its unusual phase change. In a model experiment, the material was deliberately contaminated with an additive. Heating caused the polymer to enter the vapour phase while the non-volatile contaminant remained behind. When the vapour cooled, it re-formed as a clean solid. This is a form of purification by sublimation, in which differences in volatility separate one substance from another. Conventional recycling often produces complex mixtures containing dyes, plasticisers, fillers, stabilisers and residues from previous use. The ability to separate a polymer from certain additives without transforming it through multiple liquid chemical stages could provide a useful foundation for future recycling technologies, although the method’s effectiveness will depend on the nature of the contaminant.

The scientists caution that the discovery remains a proof of concept rather than a ready-made industrial solution. A practical replacement for commodity plastics would need to match their low cost, mechanical strength, durability, production volume and resistance to environmental exposure. It would also need to be assessed over many heating and cooling cycles to determine whether the monomer, polymer or coating gradually degrades. Life-cycle studies would be required to compare the energy needed for low-temperature depolymerisation and vapour recovery with the energy used in conventional manufacturing and recycling. Nevertheless, the material’s combination of hydrophobicity, softness, reversibility and relatively low processing temperature suggests that its greatest value may lie not in replacing every plastic, but in inspiring specialised circular materials designed from the outset to be temporary, recoverable and chemically reusable.

The University of Surrey researchers describe the work as the introduction of a new design principle for polymer science: instead of making plastics permanently stable and then struggling to dispose of them, scientists could engineer materials whose stability is deliberately switchable. Touseef Kazmi, the study’s lead author, said the team had demonstrated a principle that was not previously available, while corresponding author Peter Roth said the chemistry could inspire a new generation of circular materials. The next challenge will be tailoring the molecular structure to control properties such as strength, flexibility, evaporation rate and re-polymerisation speed. If those obstacles can be overcome, plastics that vanish into recoverable vapour and return as the same material could turn a dramatic laboratory demonstration into a new route for cleaner coatings, easier maintenance and more precise polymer recycling.

Subject of Research: Reversible, sublimable polymers based on 1,2-dithiolane chemistry for low-temperature depolymerisation, vapour deposition, removable waterproof coatings and polymer purification.

Article Title: Lipoic Acid Without the Side Chain: Sublimable Homopolymers and Degradable Copolymers Based on 1,2-Dithiolane

News Publication Date: 11 August 2026

Web References: https://doi.org/10.1021/acs.macromol.6c01500

References: University of Surrey study published in Macromolecules, DOI: 10.1021/acs.macromol.6c01500

Keywords

Recyclable plastics, polymer chemistry, sublimable polymers, depolymerisation, 1,2-dithiolane, lipoic acid, vapour deposition, waterproof coatings, chemical recycling, circular materials, materials science

PTFE, a fluorine-based synthetic polymer widely known for its non-stick properties, is ubiquitous in cookware, electrical cables, and optical fiber coatings due to its exceptional chemical resilience, thermal stability, and low friction characteristics. However, these very properties that make PTFE valuable also pose significant environmental challenges, as its durability inhibits natural degradation, complicating disposal and recycling efforts. Conventional disposal methods, such as incineration and landfilling, have considerable drawbacks: incineration demands high thermal input and emits hazardous hydrogen fluoride gas, while landfilling merely postpones the environmental impact by sequestering PTFE that does not readily break down.

In contrast, defluorination — chemically dismantling PTFE to reclaim its fluorine content — offers a sustainable avenue for recycling fluorinated polymers. Despite this promise, existing defluorination techniques suffer from critical limitations. High-temperature processes often exceeding 500 °C are energy-intensive and technically demanding, while low-temperature methods employ complex reagents that reduce practical applicability. Furthermore, prior studies have inadequately addressed the efficacy of fluorine recovery, leaving uncertainty about resource recirculation potential.

The team led by Professor Norio Shibata, including contributors Taichi Araki and Hibiki Ota, responded to these challenges by developing a defluorination protocol using sodium dispersion in tetrahydrofuran (THF) solvent at ambient temperature (25 °C). This approach achieves a near-quantitative fluoride ion yield of up to 98% within a 12-hour reaction window, a remarkable feat demonstrating highly efficient fluorine liberation under mild conditions. The sodium dispersion acts as a powerful reductant, cleaving the strong carbon-fluorine bonds characteristic of PTFE’s robust polymeric structure.

Meticulous analysis of the post-reaction residue, employing spectroscopic techniques such as X-ray diffraction (XRD), Raman and infrared spectroscopy, and nuclear magnetic resonance (NMR), confirmed substantial conversion of PTFE into fluoride ions. Elemental quantification revealed that approximately 93.5% of the polymer’s original fluorine content was recovered, demonstrating the method’s exceptional recovery efficiency. Morphological studies using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX) illustrated profound physical alterations to the PTFE surface topology—transforming its dense, smooth grains into cracked, irregular black residues reflective of polymer degradation.

Crucially, the researchers extended the application of this sodium dispersion defluorination method beyond PTFE to other environmentally persistent fluorinated pollutants within the PFAS family. Compounds such as perfluorononanoic acid, perfluorooctanoic acid, perfluorobutanesulfonic acid, and trifluoroacetic acid demonstrated similarly high fluorine recovery rates up to 97%, contingent on adjustment of reaction time and reagent quantity. This versatility underscores the broad impact potential of the approach in mitigating PFAS contamination, a significant public health and ecological concern due to these substances’ widespread industrial use and resistance to conventional degradation.

Prof. Shibata emphasized the ecological and technological significance of the method: “Our defluorination technique circumvents the extreme energy requirements and harmful emissions of traditional PFAS remediation strategies, providing a viable path for both environmental pollutant degradation and sustainable fluorine resource management.” This advancement holds promise not only for waste reduction but also for reducing dependence on fluorite mineral extraction, presently the primary source of industrial fluorine, thereby advancing circular economy principles.

This research marks a pivotal stride in synthetic fluorine chemistry and environmental science by demonstrating that effective polymer breakdown and resource recovery can be achieved under mild, scalable conditions. The chemical community anticipates that this innovative defluorination strategy will inspire further studies and adaptations for industrial recycling frameworks, supporting a transition toward greener chemical processes.

The study’s publication in Nature Communications reflects its impactful contribution to fundamental and applied fluorine chemistry, detailing the experimental methodologies and comprehensive analyses underpinning its findings. The authors report no competing interests, enhancing confidence in the objectivity and integrity of the disclosure.

Beyond its immediate environmental implications, this discovery propels fluorine chemistry forward by opening new avenues for managing persistent fluorinated materials. The utilization of finely dispersed sodium as an effective reductant at ambient temperature challenges traditional assumptions about reaction energetics in high-strength C-F bond activation, creating exciting opportunities for synthetic innovation.

As the world grapples with PFAS contamination and the sustainability of fluorinated polymer use, the Nagoya Institute of Technology team’s work offers a blueprint for harnessing chemical ingenuity to balance industrial utility with environmental stewardship. Their method elegantly combines fundamental chemical principles with practical application, advancing both scientific understanding and societal benefit.

The Nagoya Institute of Technology continues its mission of marrying cutting-edge research with real-world applications, fostering solutions that address critical societal challenges while nurturing future generations of scientific innovators through robust educational programs.

Subject of Research: Not applicable

Article Title: Room-temperature defluorination of PTFE and PFAS via sodium dispersion

News Publication Date: 15-Jul-2025

Web References:
https://www.nature.com/articles/s41467-025-61819-6
http://dx.doi.org/10.1038/s41467-025-61819-6

Image Credits: Prof. Norio Shibata from Nagoya Institute of Technology, Japan

Keywords

Polytetrafluoroethylene, PTFE, PFAS, fluorine recovery, defluorination, sodium dispersion, room-temperature reaction, fluoropolymers recycling, environmental remediation, fluorine chemistry, sustainable materials, green chemistry