Tunable and Degradable Dynamic Thermosets from Compatibilized Polyhydroxyalkanoate Blends

Chen Ling; Ryan W Clarke; Gloria Rosetto; Shu Xu; Robin M Cywar; Dong Hyun Kim; Levi J Hamernik; Stefan J Haugen; William E Michener; Sean P Woodworth; Torrey M Lind; Kelsey J Ramirez; Meltem Urgun-Demirtas; Davinia Salvachúa; Christopher W Johnson; Nicholas A Rorrer; Gregg T Beckham

doi:10.1021/acssuschemeng.5c00943

Tunable and Degradable Dynamic Thermosets from Compatibilized Polyhydroxyalkanoate Blends

ACS Sustain Chem Eng. 2025 Feb 27;13(9):3817-3829. doi: 10.1021/acssuschemeng.5c00943. eCollection 2025 Mar 10.

Authors

Chen Ling^{1

2}, Ryan W Clarke^{1

3}, Gloria Rosetto¹, Shu Xu^{4

5}, Robin M Cywar¹, Dong Hyun Kim¹, Levi J Hamernik¹, Stefan J Haugen^{1

3}, William E Michener^{1

2

3}, Sean P Woodworth^{1

3}, Torrey M Lind^{1

2}, Kelsey J Ramirez^{1

2

3}, Meltem Urgun-Demirtas⁴, Davinia Salvachúa^{1

2}, Christopher W Johnson^{1

2}, Nicholas A Rorrer^{1

3}, Gregg T Beckham^{1

2

3}

Affiliations

¹ Renewable Resources and Enabling Sciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States.
² Agile BioFoundry, Emeryville, California 94608, United States.
³ BOTTLE Consortium, Golden, Colorado 80401, United States.
⁴ Applied Materials Division, Argonne National Laboratory, Lemont, Illinois 60439, United States.
⁵ Northwestern Argonne Institute of Science & Engineering, Evanston, Illinois 60208, United States.

Abstract

Polyhydroxyalkanoates (PHAs) are versatile, biobased polyesters that are often targeted for use as degradable thermoplastic replacements for polyolefins. Given the substantial chemical diversity of PHA, their potential as cross-linked polymers could also enable similar platforms for reversible, degradable thermosets. In this work, we genetically engineered Pseudomonas putida KT2440 to synthesize poly(3-hydroxybutyrate-co-3-hydroxyundecenoate) (PHBU), which contains both 3-hydroxybutyrate and unsaturated 3-hydroxyundecenoate components. To reduce the brittleness of this polymer, we physically blended PHBU with the soft copolymer poly(3-hydroxydecanonate-co-3-hydroxyundecenoate) in mass ratios of 1:3, 1:1, and 3:1. Upon observing varying degrees of immiscibility by scanning electron microscopy, we installed dynamic boronic ester cross-links via thiol-ene click chemistry, which resulted in compatibilized dynamic thermoset blends ranging in hard, medium, and soft rubber or elastomer thermomechanical profiles. These dynamic thermoset blends were subjected to controlled biological degradation experiments in freshwater conditions, achieving timely mass loss despite the cross-linked architectures. Overall, this work highlights a two-component platform for the production of degradable and reprocessable dynamic thermoset blends suitable for several classes of cross-linked polymer technologies from tailored, biological PHA copolymers.