{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,29]],"date-time":"2026-08-29T10:51:18Z","timestamp":1788000678258,"version":"build-2784847793"},"reference-count":41,"publisher":"MDPI AG","issue":"18","license":[{"start":{"date-parts":[[2025,9,22]],"date-time":"2025-09-22T00:00:00Z","timestamp":1758499200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"NEDO","award":["JPNP18016"],"award-info":[{"award-number":["JPNP18016"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Polymers"],"abstract":"<jats:p>This study aimed to evaluate the physical properties and biodegradability of sulfur-vulcanized polyhydroxyalkanoates (PHAs) with unsaturated side chains. As a vulcanizable PHA, poly(3-hydroxybutyrate-co-3-hydroxy-5-hexenoate) [P(3HB-co-3H5HE)] was biosynthesized with a 3H5HE fraction of 3\u201347 mol% using recombinant Escherichia coli and subsequently vulcanized with varying sulfur contents (2\u201320 per hundred resin, phr) in the presence of zinc oxide, stearic acid, and 2-mercaptobenzothiazole as curing agents. The vulcanized PHA copolymers were insoluble in chloroform, indicating the formation of a cross-linked network. Raman spectroscopy revealed the functional loss of the double bonds in the polymers. After the vulcanization with 5 phr sulfur, the tensile strength and elongation at break of P(3HB-co-47 mol% 3H5HE) increased from 0.6 MPa to 6.3 MPa and from 430% to 813%, respectively. This sample exhibited low tensile set (8%) after 200% elongation, indicating rubber-like properties. Although biodegradability decreased with increasing crosslink density, vulcanized P(3HB-co-3H5HE) exhibited a greater degradation potential than vulcanized rubber but was lower than that of non-vulcanized P(3HB-co-3H5HE). These findings demonstrate that sulfur vulcanization can enhance the resilience of unsaturated PHAs, making them suitable for elastomeric and environmental applications.<\/jats:p>","DOI":"10.3390\/polym17182561","type":"journal-article","created":{"date-parts":[[2025,9,22]],"date-time":"2025-09-22T17:08:17Z","timestamp":1758560897000},"page":"2561","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Sulfur Vulcanization and Material Properties of Polyhydroxyalkanoates with Unsaturated Side Chain"],"prefix":"10.3390","volume":"17","author":[{"given":"Phimthong","family":"Khamjapo","sequence":"first","affiliation":[{"name":"Department of Materials Science and Engineering, Institute of Science Tokyo, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0077-6485","authenticated-orcid":false,"given":"Lucas Vinicius Santini","family":"Ceneviva","sequence":"additional","affiliation":[{"name":"Department of Materials Science and Engineering, Institute of Science Tokyo, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yusuke","family":"Nakata","sequence":"additional","affiliation":[{"name":"Department of Materials Science and Engineering, Institute of Science Tokyo, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4781-5760","authenticated-orcid":false,"given":"Yuki","family":"Miyahara","sequence":"additional","affiliation":[{"name":"Department of Materials Science and Engineering, Institute of Science Tokyo, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Takeharu","family":"Tsuge","sequence":"additional","affiliation":[{"name":"Department of Materials Science and Engineering, Institute of Science Tokyo, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,9,22]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"278","DOI":"10.1111\/1751-7915.12129","article-title":"Biotechnological strategies to improve production of microbial poly-(3-hydroxybutyrate): A review of recent research work","volume":"7","author":"Pena","year":"2014","journal-title":"Microb. 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