Synthetic biodegradable polyhydroxyalkanoates (PHAs): Recent advances and future challenges

Westlie, Andrea H.; Quinn, Ethan C.; Parker, Celine R.; Chen, Eugene Y.‐X.

doi:10.1016/j.progpolymsci.2022.101608

Cited by 72 publications

(49 citation statements)

References 148 publications

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“…Among several strategies − being developed to combat the current plastic problem, − biobased and biodegradable polymers − offer a more sustainable and environmentally benign alternative to the petroleum-based and nondegradable incumbent plastics. In particular, polyhydroxyalkanoates (PHAs), a class of biopolymers that can be synthesized biologically − and chemocatalytically, − are biodegradable in ambient environments, thus attracting intense interest. Purely isotactic poly(3-hydroxybutyrate) ( it -P3HB), the most commonly produced PHA, exhibits several favorable properties including high crystallinity, melting transition temperature ( T m , 170–180 °C), and ultimate tensile strength (σ B = ∼35 MPa), as well as excellent barrier properties.…”

Section: Introductionmentioning

confidence: 99%

“…Biological routes produce isotactic ( R )-polymers or copolymers of largely random sequences with dispersity ( D̵ ) ≥2 due to the step-growth polymerization mechanism. ,− , Chemical synthesis of PHA that operates on the catalyzed ring-opening polymerization (ROP) proceeds via a rapid chain-growth mechanism, which comes with the advantages of faster reaction kinetics and precision control over both PHA chain structures (predictable number-average molar mass ( M n ) and low-to-near unity D̵ values) and stereo-microstructures (tacticities) . For example, the ROP of β-butyrolactone (β-BL) produces diverse P3HB materials that are atactic ( at ), − iso-rich, − and syndiotactic ( st ) or syndio-rich ( sr ). − The ROP of racemic eight-membered dimethyl diolide ( rac -8DL Me ) catalyzed by C 2 -chrial salen-based metal complexes results in biomimetic it -P3HB .…”

Section: Introductionmentioning

confidence: 99%

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Installing Controlled Stereo-Defects Yields Semicrystalline and Biodegradable Poly(3-Hydroxybutyrate) with High Toughness and Optical Clarity

et al. 2023

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Stereo-defects present in stereo-regular polymers often diminish thermal and mechanical properties, and hence suppressing or eliminating them is a major aspirational goal for achieving polymers with optimal or enhanced properties. Here, we accomplish the opposite by introducing controlled stereo-defects to semicrystalline biodegradable poly(3-hydroxybutyrate) (P3HB), which offers an attractive biodegradable alternative to semicrystalline isotactic polypropylene but is brittle and opaque. We enhance the specific properties and mechanical performance of P3HB by drastically toughening it and also rendering it with the desired optical clarity while maintaining its biodegradability and crystallinity. This toughening strategy of stereo-microstructural engineering without changing the chemical compositions also departs from the conventional approach of toughening P3HB through copolymerization that increases chemical complexity, suppresses crystallization in the resulting copolymers, and is thus undesirable in the context of polymer recycling and performance. More specifically, syndio-rich P3HB (sr-P3HB), readily synthesized from the eight-membered mesodimethyl diolide, has a unique set of stereo-microstructures comprising enriched syndiotactic [rr] and no isotactic [mm] triads but abundant stereo-defects randomly distributed along the chain. This sr-P3HB material is characterized by high toughness (U T = 96 MJ/m 3 ) as a result of its high elongation at break (>400%) and tensile strength (34 MPa), crystallinity (T m = 114 °C), optical clarity (due to its submicron spherulites), and good barrier properties, while it still biodegrades in freshwater and soil.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Installing Controlled Stereo-Defects Yields Semicrystalline and Biodegradable Poly(3-Hydroxybutyrate) with High Toughness and Optical Clarity

et al. 2023

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“…They possess tunable thermomechanical properties and are biodegradable in the ambient environment, thus offering a more sustainable alternative to petroleum-derived and/or nondegradable plastics. Over the past 60+ years, the ring-opening polymerization (ROP) of four-membered blactones, such as b-butyrolactone (b-BL), and their derivatives with different substituents at a and b positions has been extensively studied to enable the chemical synthesis of PHAs, particularly poly(3-hydroxybutyrate) (P3HB), with atactic, iso-rich, syndio-rich, or syndiotactic stereomicrostructures (tacticities) (9)(10)(11)(12)(13)(14)(15)(16). More recently, purely isotactic P3HB that has a number-average molar mass (M n ) of 154 kDa, a narrow dispersity (Đ) of 1.01, and a high melting-transition temperature (T m ) of 171°to 175°C (17); stereo-sequenced PHAs (18); polyolefin-like PHA copolymers (19); and alternating isotactic PHAs (20) have also been realized through the ROP of eight-membered dialkyl diolides (8DL R ).…”

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confidence: 99%

“…Polyhydroxyalkanoates (PHAs) are a class of polyester naturally accumulated biologically by living microorganisms ( 1 – 8 ) or synthetically produced chemocatalytically ( 9 , 10 ) from diverse feedstocks, especially biorenewable sources. They possess tunable thermomechanical properties and are biodegradable in the ambient environment, thus offering a more sustainable alternative to petroleum-derived and/or nondegradable plastics.…”

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confidence: 99%

Chemically circular, mechanically tough, and melt-processable polyhydroxyalkanoates

Zhou

Zhang

Shi

et al. 2023

Science

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Polyhydroxyalkanoates (PHAs) have attracted increasing interest as sustainable plastics because of their biorenewability and biodegradability in the ambient environment. However, current semicrystalline PHAs face three long-standing challenges to broad commercial implementation and application: lack of melt processability, mechanical brittleness, and unrealized recyclability, the last of which is essential for achieving a circular plastics economy. Here we report a synthetic PHA platform that addresses the origin of thermal instability by eliminating α-hydrogens in the PHA repeat units and thus precluding facile cis-elimination during thermal degradation. This simple α,α-disubstitution in PHAs enhances the thermal stability so substantially that the PHAs become melt-processable. Synergistically, this structural modification also endows the PHAs with the mechanical toughness, intrinsic crystallinity, and closed-loop chemical recyclability.

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“…In addition to the very promising copolymerization of epoxide with carbon monoxide, [44] the ROP of four-or eight-membered cyclic esters is an alternative route for the synthesis of PHAs. [45] In the 1990s, Seebach [46] and Höcker [47] et al reported that the thermolysis of naturally produced enantiopure P3HB at 200-300 °C yielded linear oligomers with ω-crotonate end groups and crotonic acid, while solution degradation yielded cyclic oligomer mixtures (trimer as the major product), in addition, the corresponding repolymerization only afforded P3HB with a low M n of 5 kDa. Therefore, the low yield upon depolymerization and less efficiency for repolymerization underline the nonrecyclability of the PHA family (Figure 10).…”

Section: Commercial Polyestersmentioning

confidence: 99%

Emerging Trends in Closed‐Loop Recycling Polymers: Monomer Design and Catalytic Bulk Depolymerization

Liu

2023

Chemistry A European J

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Plastics are indispensable materials in modern society; however, their extensive use has contributed to the depletion of finite natural resources and caused severe environmental issues. One end-of-use solution for plastics involves the chemical recycling of polymers back to monomers for repolymerization to virgin polymers without changing the material properties, allowing the establishment of a circular material economy. This concept focuses on the critical advantages of chemically recyclable polymers in terms of monomer design, material properties, and the feasibility of bulk depolymerization. The recyclability via bulk thermolysis of various polyesters, CO 2 -based polycarbonates, and polyacetals produced via ring-opening polymerization is highlighted through discussions regarding rational monomer design and efficient catalyst development. An outlook and perspective are provided to delineate the future challenges in the rational design of monomer and polymer structures that deliver the desired materials performance while being suitable for bulk thermolysis with high (de)polymerization activity and selectivity.

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Synthetic biodegradable polyhydroxyalkanoates (PHAs): Recent advances and future challenges

Cited by 72 publications

References 148 publications

Installing Controlled Stereo-Defects Yields Semicrystalline and Biodegradable Poly(3-Hydroxybutyrate) with High Toughness and Optical Clarity

Installing Controlled Stereo-Defects Yields Semicrystalline and Biodegradable Poly(3-Hydroxybutyrate) with High Toughness and Optical Clarity

Chemically circular, mechanically tough, and melt-processable polyhydroxyalkanoates

Emerging Trends in Closed‐Loop Recycling Polymers: Monomer Design and Catalytic Bulk Depolymerization

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