{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,12,15]],"date-time":"2025-12-15T10:19:22Z","timestamp":1765793962686,"version":"3.48.0"},"reference-count":19,"publisher":"MDPI AG","issue":"24","license":[{"start":{"date-parts":[[2025,12,13]],"date-time":"2025-12-13T00:00:00Z","timestamp":1765584000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100000266","name":"Engineering and Physical Sciences Research Council","doi-asserted-by":"publisher","award":["EP\/W018977\/1"],"award-info":[{"award-number":["EP\/W018977\/1"]}],"id":[{"id":"10.13039\/501100000266","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Polymers"],"abstract":"<jats:p>This study explores a disulfide-selective cross-linking strategy for natural rubber (NR) to formulate elastomeric materials with engineering-relevant mechanical properties. A disulfide-containing bismaleimide (BIS) cross-linker was synthesized from cystamine and maleic anhydride and compounded with NR. Three formulations were prepared: control (no inhibitor), CuCl2-based, and copper(II) methacrylate (CuMA) based compounds, with BIS concentrations ranging from 3.55 to 8.88 phr. Rheological and mechanical testing revealed that CuCl2 formulations suffered from molecular degradation, poor thermal stability, and mechanical brittleness due to oxidative reactions in the absence of antioxidants. In contrast, CuMA-based compounds exhibited intermediate molecular weights prior to curing, stable thermal behavior, and improved mechanical properties, including enhanced torque and tensile strength, indicating effective cross-linking and partial recyclability. The control formulations also performed reasonably well but did not match the mechanical strength of conventional sulfur-vulcanized NR. The results demonstrate that metal coordination, particularly with CuMA, can modulate disulfide metathesis kinetics and offer a pathway to thermally triggered network rearrangement. Overall, CuMA emerges as a promising candidate for developing high-performance, recyclable rubber materials, while CuCl2 requires further stabilization strategies. This work establishes a baseline for future recyclability studies and advances the design of dynamic covalent networks in elastomers.<\/jats:p>","DOI":"10.3390\/polym17243302","type":"journal-article","created":{"date-parts":[[2025,12,15]],"date-time":"2025-12-15T10:11:23Z","timestamp":1765793483000},"page":"3302","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Alternative Natural Rubber Cross-Linking Utilizing a Disulfide-Containing Bismaleimide"],"prefix":"10.3390","volume":"17","author":[{"ORCID":"https:\/\/orcid.org\/0009-0003-4791-6032","authenticated-orcid":false,"given":"Anureet","family":"Kaur","sequence":"first","affiliation":[{"name":"School of Engineering and Materials Science, Queen Mary University of London, London E1 4NS, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Maria","family":"Tucker","sequence":"additional","affiliation":[{"name":"School of Engineering and Materials Science, Queen Mary University of London, London E1 4NS, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1872-677X","authenticated-orcid":false,"given":"Keizo","family":"Akutagawa","sequence":"additional","affiliation":[{"name":"School of Engineering and Materials Science, Queen Mary University of London, London E1 4NS, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6465-2871","authenticated-orcid":false,"given":"Biqiong","family":"Chen","sequence":"additional","affiliation":[{"name":"Department of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8304-7140","authenticated-orcid":false,"given":"James J. C.","family":"Busfield","sequence":"additional","affiliation":[{"name":"School of Engineering and Materials Science, Queen Mary University of London, London E1 4NS, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2025,12,13]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"212","DOI":"10.1038\/s43246-024-00651-9","article-title":"Recyclable sulfur cured natural rubber with controlled disulfide metathesis","volume":"5","author":"Kaur","year":"2024","journal-title":"Commun. Mater."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Markl, E., and Lackner, M. (2020). Devulcanization Technologies for Recycling of Tire-Derived Rubber: A Review. 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