Polyethylene is cheap, tough and everywhere, but it is notoriously hard to glue, print on or bond to other materials. Chemists at the University of California, Berkeley and two US national laboratories report in Nature that a tiny amount of an iron catalyst can convert part of a polyethylene surface into ketone groups below 80°C. Adhesion to polar materials rose up to 90-fold while the plastic’s bulk strength and melting point were preserved. The results are from laboratory tests and have not yet been demonstrated at industrial scale.
Polyethylene is the plastic of milk pouches, carry bags, food films, water tanks and pipes. It is made by linking ethylene molecules into long chains of carbon and hydrogen, and that simple chemistry gives it its virtues: it is inexpensive, chemically resistant and strong. The same chemistry makes it frustrating. Its surface consists almost entirely of non-polar carbon–hydrogen bonds, so inks, paints, glues and other polar materials adhere poorly. Manufacturers often resort to energy-intensive surface treatments such as flame, corona discharge or plasma, or add extra layers and adhesives. Those fixes complicate recycling, especially for the multilayer films used in packaging.
A paper published online in Nature on 13 October describes a more precise approach. The team, led by chemist John F. Hartwig of the University of California, Berkeley, with colleagues at Lawrence Berkeley National Laboratory and the Advanced Photon Source at Argonne National Laboratory, reports what it calls the selective, catalytic oxidation of polyethylene surfaces. The first author is Cristian P. Woroch. The paper was received on 4 May and accepted on 6 October, and has been published as an accelerated article preview, which may be revised before the final version.
The chemistry
Polymer chemists have long been able to add functional groups to polyolefins, but usually by dissolving or melting the polymer and reacting the whole of it. That changes the bulk material: it can lower the melting point, reduce crystallinity and weaken the plastic. The Berkeley team took a different route. They reacted solid polyethylene at a solid–liquid interface, so that the chemistry happens only at the surface.
The reaction converts some of the methylene (CH₂) units in the polymer chains into ketones, carbonyl groups in which a carbon atom is double-bonded to oxygen. Ketones are polar, so they interact strongly with polar materials such as many adhesives, coatings and metal oxides. The reaction uses an iron catalyst at a loading of just 0.001 mole per cent, runs below 80°C, and uses what the authors describe as inexpensive oxidants. The abstract does not name the oxidant, and NSH has not been able to read the full methods.
Iron is an attractive choice. It is abundant, cheap and of low toxicity compared with the precious metals often used in catalysis, which matters for any process that might eventually be applied to millions of tonnes of plastic.
What they found
According to the paper’s abstract:
- Adhesion: the treated surfaces adhered to polar surfaces up to 90 times more strongly than untreated polyethylene.
- Selectivity matters: adhesion was up to four times stronger than that of polyethylene functionalised to a comparable extent in a uniform medium, where the reaction is spread through the material.
- Bulk properties retained: the melting temperature and tensile strength of the polyethylene were maintained, although the abstract gives no numerical values.
- Durability: the surface properties persisted longer than those produced by less selective oxidation methods. Conventional treatments such as corona discharge are known to fade over time as the polymer surface rearranges.
- Further tuning: the surface ketones can be modified chemically to increase adhesive strength further.
Why it is interesting
The work addresses a long-standing trade-off in polymer engineering. Making plastics more versatile usually means adding components, such as tie-layers, primers, compatibilisers or other polymers, and each addition makes the material harder to recycle. If a single-material polyethylene film could be made printable and bondable by modifying only its outermost layer, packaging designers might rely less on multilayer laminates that combine different plastics and are difficult to separate.
The selectivity is the conceptual advance. By confining the chemistry to the surface, the method treats the plastic like a substrate to be finished rather than a chemical to be transformed. This is consistent with Hartwig’s broader research programme on selective carbon–hydrogen functionalisation, which seeks to modify specific C–H bonds in complex molecules rather than relying on harsher, less controlled reactions.
Limitations
Important questions remain, and the available text does not answer them. The “up to” figures are best-case values; the abstract does not state the substrates tested, the adhesion-test conditions or the timescales over which durability was assessed. There is no information yet on cost, throughput, solvent use or how the process would integrate with high-speed film lines, which currently use corona treatment because it is fast and continuous. No university press release or independent expert comment was available at the time of writing. The work is a laboratory demonstration, and its industrial value will depend on scale-up.
Why it matters for India
India is one of the world’s largest consumers of polyethylene, used heavily in packaging, agriculture (mulch films, irrigation pipes, water tanks) and infrastructure. The country’s plastic-waste management rules increasingly push producers towards recyclable and mono-material packaging under extended producer responsibility. Technologies that make polyethylene printable and bondable without multilayer construction could, if proven at scale, help Indian converters meet those obligations. The chemistry itself is accessible: a base-metal catalyst, mild temperatures and inexpensive reagents are the kind of conditions Indian chemical research groups and industry could readily explore.
What comes next
The researchers point to further tuning of the surface chemistry. The decisive tests will come from engineering: continuous processing, compatibility with food-contact regulations, long-term ageing, and whether treated surfaces survive mechanical recycling.
–Sasikiran U Kanteti
Key facts
- Paper: Woroch C.P., Klivansky L., McCarthy D.P., … Helms B.A., Hartwig J.F. “Selective, Catalytic Oxidation of Polyethylene Surfaces.” Nature, published online 13 Oct 2026 (accelerated article preview). DOI: 10.1038/s41586-026-11255-3.
- Institutions: UC Berkeley (Chemistry); Lawrence Berkeley National Laboratory (Molecular Foundry, Materials Sciences, Advanced Light Source); Argonne National Laboratory (Advanced Photon Source).
- Conditions: iron catalyst at 0.001 mol%; below 80°C; inexpensive oxidants (not named in the abstract).
- Results: CH₂ to ketone at the surface only; adhesion to polar surfaces up to 90-fold higher; up to 4-fold better than uniform-medium functionalisation; melting point and tensile strength retained.
- Status: laboratory study; no scale-up or cost data.
