Scalable production of critically thin polyethylene films via multistep stretching | Nature Chemical Engineering

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Plastic films are among the most used materials. In many applications, both high strength and low thickness are required. The thickness of free-standing plastic films has recently been reduced to micrometres, 200 nm and even 60 nm. Pushing this boundary further faces considerable challenges, as processability conflicts with stability at the ‘ultrathin’ scale (below ~100–200 nm). Here, to overcome this trade-off, we modulated the entanglement density of plastic chains to identify a maximum stretching processing window. Then, relaxation was introduced during stretching to kinetically stabilize the ultrathin film. Combined, polyethylene film thicknesses were reduced to ~12 nm, near its critical thickness. This critically thin polyethylene reveals physical properties different from its bulk counterparts, such as high mechanical strength (113.9 GPa (g cm–3)–1), abnormal interfacial properties and a high aspect ratio near 108. Potential applications of these films include nuclear fusion ignition support and thin breathable epidermal sensors. Our work reveals advanced processing strategies, distinctive properties and broader applications of plastic films near the processing limit.

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Q.F. and R.L. acknowledge support from the National Natural Science Foundation of China (grant nos. 52233002, 52103042 and 22341304), State Key Laboratory of Polymer Materials Engineering grant (no. sklpme2022-3-09) and the Provincial Natural Science Foundation of Sichuan (grant no. 24NSFSC6554). We also thank B. Tee and Z. Wang for help with the fabrication of conformation sweat sensors. We thank B. Zhang for help with the in situ AFM during heating. We thank Q. Huang for the elongational rheology experiments. We thank K. Zhang for help in several characterizations and Z. Su for his generous support in the cryo-EM observations.

These authors contributed equally: Runlai Li, Zirui Wang.

College of Polymer Science and Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu, China

Runlai Li, Zirui Wang, Weilong Sun, He Zhang, Hua Deng & Qiang Fu

State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Fudan University, Shanghai, China

Yuwen Zeng

School of Materials Science and Engineering, Peking University, Beijing, China

Xiaoxu Zhao

State Key Lab of Coordination Chemistry, Department of Polymer Science and Engineering, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, China

Wenbing Hu

Department of Chemistry, National University of Singapore, Singapore, Singapore

Kian Ping Loh

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Q.F. conceived the idea and guided the project. R.L., Z.W., W.S. and H.Z. prepared the C-PE and performed the characterizations. K.P.L. designed the sweat sensor demonstration and assisted in the C-PE preparation. Y.Z. contributed the indentation tests, and X.Z. performed the HRTEM tests. W.H. and H.D. assisted in the data visualization. Q.F., R.L. and Z.W. co-wrote the paper. All the authors analysed the data, commented on the paper and agreed with the paper.

Correspondence to Qiang Fu.

The authors declare no competing interests.

Nature Chemical Engineering thanks Mukerrem Cakmak, Phil Coates, Guo-Hua Hu and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

a, Photographs of C-PE films to demonstrate transparency. b, Scanning-electron-miscropscopy images of C-PE films displaying a library of fibrous crystalline structures.

a-c, Mw-Conc diagrams on the thickness, stretch ratios and tensile moduli of prepared C-PE. d, The definition of C-PE processing window, the FQ isorheic line and the FQ line deviation index (FQ-DI). e, Conc-Mw phase diagram on FQ-DI. f, Classification of four regions based on the diagram in (e) according to the processability of precursors.

Source data

a, Scheme of FCP supporting nuclear fuel capsule inside the hohlraum during fusion ignition. b, C-PE’s stable adherence to the wrist was maintained even after one-minute exposure to intense tap water flushing. The upper inset captures C-PE post-flushing, while the lower inset provides a microscopic view of the C-PE boundary on a skin replica, with C-PE parts pseudo-colored in blue. Scale bar: 400 µm. c, A four-channel sweat sensor is integrated on C-PE with self-conformability. Inset, the schema of C-PE-based sweat sensor spontaneously conformed on human skin, detecting Na+, K+, Ca2+ ions, glucose and temperature.

Supplementary Sections 1–10, Figs. 1–86, Tables 1 and 2, and discussion.

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Li, R., Wang, Z., Sun, W. et al. Scalable production of critically thin polyethylene films via multistep stretching. Nat Chem Eng (2024). https://doi.org/10.1038/s44286-024-00139-w

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Received: 01 March 2024

Accepted: 04 October 2024

Published: 01 November 2024

DOI: https://doi.org/10.1038/s44286-024-00139-w

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