{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,22]],"date-time":"2026-06-22T14:25:34Z","timestamp":1782138334558,"version":"3.54.5"},"reference-count":68,"publisher":"American Association for the Advancement of Science (AAAS)","issue":"51","funder":[{"DOI":"10.13039\/501100001843","name":"Science and Engineering Research Board","doi-asserted-by":"publisher","award":["CRG\/568\/2022"],"award-info":[{"award-number":["CRG\/568\/2022"]}],"id":[{"id":"10.13039\/501100001843","id-type":"DOI","asserted-by":"publisher"}]},{"name":"J.C. Bose National fellowship","award":["JCB\/2023\/000039"],"award-info":[{"award-number":["JCB\/2023\/000039"]}]}],"content-domain":{"domain":["www.science.org"],"crossmark-restriction":true},"short-container-title":["Sci. Adv."],"published-print":{"date-parts":[[2025,12,19]]},"abstract":"<jats:p>Helical polymers are fascinating materials, yet retaining their helicity in the solid state remains a key challenge for practical applications. Here, we present a regiospecific topochemical azide-alkyne cycloaddition for synthesizing crystalline covalent helical polymers via a single\u2013crystal\u2013to\u2013single\u2013crystal transformation. Building on our prior glycine-proline\u2013based systems, we investigated the effect of subtle modification: introducing a hydroxyl group to the proline unit. This minor change induced a helicity reversal (left- to right-handed) and a substantial reduction in pitch (8.9 to 4.9 \u00c5). Single-crystal x-ray diffraction revealed that this profound reordering is driven by intra- and intermolecular hydrogen bonds (C\u2500H\u22efO and O\u2500H\u22efN), acting as supramolecular bridges between helices, enabling denser packing. Consequently, the glycine-hydroxyproline\u2013based polymer exhibited markedly enhanced mechanics, with a Young\u2019s modulus of 18.57\u00a0\u00b1\u00a02.01 GPa and hardness of 1.09\u00a0\u00b1\u00a00.13 GPa, surpassing natural collagen. This study provides insights into controlling polymer topology and mechanics through subtle modifications, establishing a powerful paradigm for the design of next-generation helical materials with tailored functionalities.<\/jats:p>","DOI":"10.1126\/sciadv.aeb5332","type":"journal-article","created":{"date-parts":[[2025,12,17]],"date-time":"2025-12-17T18:59:52Z","timestamp":1765997992000},"update-policy":"https:\/\/doi.org\/10.34133\/aaas_crossmark","source":"Crossref","is-referenced-by-count":1,"title":["A hydroxyl group dictates handedness, pitch, and mechanics in a crystalline covalent helical polymer"],"prefix":"10.1126","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-2143-7626","authenticated-orcid":true,"given":"Ravichandran","family":"Khazeber","sequence":"first","affiliation":[{"name":"School of Chemistry, IISER Thiruvananthapuram, Kerala, 695551 (India)."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0000-4966-0999","authenticated-orcid":true,"given":"Divina","family":"Xavier","sequence":"additional","affiliation":[{"name":"School of Chemistry, IISER Thiruvananthapuram, Kerala, 695551 (India)."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4005-3655","authenticated-orcid":true,"given":"Kana M.","family":"Sureshan","sequence":"additional","affiliation":[{"name":"School of Chemistry, IISER Thiruvananthapuram, Kerala, 695551 (India)."}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"221","reference":[{"key":"e_1_3_2_2_2","doi-asserted-by":"publisher","DOI":"10.1038\/nnano.2017.42"},{"key":"e_1_3_2_3_2","doi-asserted-by":"publisher","DOI":"10.1007\/s10509-006-1984-6"},{"key":"e_1_3_2_4_2","doi-asserted-by":"publisher","DOI":"10.1021\/acs.chemrev.6b00354"},{"key":"e_1_3_2_5_2","doi-asserted-by":"publisher","DOI":"10.1038\/171737a0"},{"key":"e_1_3_2_6_2","unstructured":"B. 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