Epoxy Vitrimer Materials by Lipase-Catalyzed Network Formation and Exchange Reactions

Area of Science:

• Polymer Chemistry
• Biocatalysis
• Materials Science

Background:

• Epoxy vitrimers offer dynamic covalent networks for reprocessing, but often require high temperatures for network exchange.
• Traditional catalysts can lead to phase separation or sedimentation at lower curing temperatures, limiting enzyme protection.
• Enzyme-catalyzed reactions present a sustainable alternative for polymer network formation and modification.

Purpose of the Study:

• To develop a fully biocatalyzed process for epoxy vitrimer preparation and reprocessing using lipase enzymes.
• To overcome limitations of low-temperature curing by utilizing binary phase diagrams for monomer selection.
• To demonstrate the catalytic efficiency of embedded lipase TL in transesterification and assess material recyclability.

Main Methods:

• Utilized binary phase diagrams to select appropriate diacid/diepoxide monomer compositions for enzyme-compatible curing below 100 °C.
• Employed lipase TL as a biocatalyst for both network formation and transesterification reactions within the epoxy vitrimer.
• Conducted multiple stress relaxation experiments at 70-100 °C to evaluate exchange reactions and material reprocessing capabilities.

Main Results:

• Successfully prepared and reprocessed epoxy vitrimers using a fully biocatalyzed approach with lipase TL.
• Demonstrated efficient transesterification and complete recovery of mechanical strength after up to three reprocessing cycles at 70-100 °C.
• Observed a loss of stress relaxation ability above 150 °C due to enzyme denaturation, highlighting the temperature limitations of biocatalysis.

Conclusions:

• Lipase-catalyzed epoxy vitrimers provide a viable route for sustainable material reprocessing at lower temperatures compared to traditional methods.
• The developed biocatalyzed vitrimers are complementary to organocatalyzed systems, offering distinct advantages in specific temperature regimes.
• Enzyme stability is a critical factor, with denaturation occurring at elevated temperatures, necessitating careful process control.