Evaluation of the effect of the number of methylene units in poly(ω-hydroxyalkanoate)s on their biodegradability

• Published in: Polymer degradation and stability 2024-04, Vol.222, p.110701, Article 110701
• Main Authors: Tsutsuba, Toyokazu, Sawanaka, Yuta, Suzuki, Miwa, Inagaki, Kana, Arai, Kana, Okaniwa, Syusuke, Torii, Junko, Tachibana, Yuya, Kasuya, Ken-ichi
• Format: Article
• Language: English
• Subjects: Aliphatic polyester; Biodegradable polymers; BOD biodegradation; Poly(ε-caprolactone) (PCL); Poly(ω-hydroxyalkanoate) (PωHA)
• ISSN: 0141-3910; 1873-2321
• DOI: 10.1016/j.polymdegradstab.2024.110701

•Five poly(ω-hydroxyalkanoate) (PωHA)s with varying numbers of methylene units were synthesized by ring opening polymerization of corresponding lactones.•The thermal properties, crystallinity, and mechanical properties of PωHAs were evaluated by TGA, DSC, WAXD measurements, and tensile test, respectively.•The clear-zone formation testing exhibits that the PPdL-degrading enzyme was not found, suggesting that the primary structure of PωHAs can endure enzymatic hydrolysis.•The BOD biodegradation testing of the hydrolysates of PωHAs revealed that they were metabolized by environmental microorganisms.•PVL, PCL, PEL, and POL showed BOD biodegradability, whereas PPdL did not. Poly(ε-caprolactone) (PCL), a type of liner poly(ω-hydroxyalkanoate)s (PωHA)s, is a commercially available biodegradable polymer. The series of PωHAs with different number of methylene units has been also regarded to be a biodegradable polymer. Although the chemical structure of PωHAs strongly affects their biodegradability, the effect of the number of methylene units in PωHAs on their biodegradability has not yet been evaluated. In this study, we synthesized five PωHAs, poly(δ-valerolactone) (PVL; n = 4), PCL (n = 5), poly(ζ-enantholactone) (PEL; n = 6), poly(η-octalactone) (POL; n = 7), and poly(ω-pentadecanolactone) (PPdL) (n = 14); subsequently, we evaluated their biodegradability via clear-zone formation and biochemical oxygen demand (BOD) biodegradation testing. PVL, PCL, PEL, and POL and their hydrolysates showed good BOD biodegradability, whereas PPdL did not show BOD biodegradability despite the biodegradability of its hydrolysate with soil inocula. These results indicate that the number of methylene units in PωHAs affects their biodegradability. [Display omitted]