Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.polymer.2025.129164

Web of Science

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/pi.6747

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Language：English   Publishing type：Research paper (scientific journal)  

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 3-47 mol% using recombinant Escherichia coli and subsequently vulcanized with varying sulfur contents (2-20 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.

DOI： 10.3390/polym17182561

PubMed

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Language：English   Publishing type：Research paper (scientific journal)  

Poly[(R)-3-hydroxybutyrare-co-(R)-3-hydroxypivalate] (P(3HB-co-3HPi)) films, a type of polyhydroxyalkanoate (PHA), are oxidized using photoactivated chlorine dioxide radical (ClO2•) gas to generate carboxyl groups and loaded with divalent metal cations, including Cu2+, Zn2+, and Ca2+ ions, via ionic interactions. The P(3HB-co-3HPi) films loaded with Cu2+ ions exhibit enhanced antibacterial activity against Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli) compared with untreated P(3HB-co-3HPi) films. In seawater, the biodegradation of these Cu2+ and Zn2+-loaded films is initially inhibited by the antimicrobial activity of the cations and occurs gradually; therefore, loading antimicrobial divalent metal cations onto the surface of PHAs inhibits biodegradation in seawater temporarily but allows biodegradation to occur with time. These results indicate that PHAs could be employed in seawater without undergoing biodegradation, such that PHAs could be used in fishing gear, including fishing lines that are repeatedly exposed to seawater for short periods.

DOI： 10.1002/mabi.202500162

PubMed

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Language：English   Publishing type：Research paper (scientific journal)  

Bacterially produced poly[(R)-3-hydroxybutyrate] (P3HB) was subjected to an alcoholysis reaction to produce low-molecular-weight (Mn ≈ 10,000 g mol-1) hydroxy-terminated P3HB (LMPHB). Using diethyl zinc as a catalyst, LMPHB was reacted with the cyclic monomers ε-caprolactone and l-lactide in separate ring-opening polymerization (ROP) reactions to produce PHB-b-PCL (PHBCL) and PHB-b-PLA (PHBLA) AB-type crystalline-crystalline diblock copolymers with varying PCL and PLA block lengths. 1H NMR and GPC were used to confirm the structure of the polymers. DSC was used to measure the thermal properties as well as assessing crystallization. A single-shifting Tg for PHBLA showed the two blocks to be miscible in the melt. The TGA results indicate enhanced thermal stability over the homopolymer P3HB. A study of the crystallization was undertaken by combining WAXD, a second DSC heating regime, and POM. POM showed that the crystallization in PHBCL to be dependent on the crystallization temperature more so than PHBLA, whose composition appeared to be the more definitive factor determining the spherulitic morphology. The results informed the crystallization temperatures used in the production of the melt-crystallized thin films that were imaged using AFM. AFM images showed unique surface morphologies dependent on the diblock copolymer composition, block length, and crystallization temperature. Finally, the enzymatic degradation studies showed these unique surface morphologies to influence how these block copolymers were degraded by enzymes.

DOI： 10.3390/polym17111558

PubMed

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Language：Japanese  

J-GLOBAL

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