Epoxy-Derived Covalent Adaptable Networks for Recyclable Thermosets
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Solution Overview
Problem
Current epoxy materials, despite their desirable properties, are irreversible thermosets that cannot be reshaped, recycled, or repaired, leading to significant waste generation and limitations in application range due to slow exchange kinetics, catalyst dependency, and potential for dark or colored materials.
Innovation Solution
Development of epoxy-derived covalent adaptable networks (CANs) based on a combination of vinylogous urethane, vinylogous urea, or vinylogous amide functions with free amines, allowing for transamination and achieving vitrimer behavior over a wide range of monomers and monomer ratios, with low relaxation times and transparency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If epoxy thermoset materials are used, then mechanical properties and chemical resistance are improved, but the ability to reshape, recycle, or repair is lost
Solution Approach 1:
The patent introduces dynamic covalent bonds (vinylogous urethane, urea, and amide linkages) into the epoxy network that can exchange and rearrange under thermal activation. This dynamic character allows the material to transition from a rigid permanent network to a reconfigurable network, enabling reshaping, recycling, and repair while maintaining the cross-linked structure's mechanical integrity.
Solution Approach 2:
The patent utilizes temperature as a controlling parameter to activate bond exchange reactions. At elevated temperatures, the vinylogous bonds undergo transamination and exchange reactions that allow network reconfiguration. This parameter-driven transformation enables the material to switch between a stable thermoset state at room temperature and a reprocessable state at elevated temperatures.
2Productivity
If catalysts are used to achieve bond exchange, then exchange kinetics are improved, but material complexity and potential discoloration increase
Solution Approach 1:
The patent employs the material's own functional groups (free amines and vinylogous carbonyl groups) to catalyze the bond exchange reactions. The amine groups act as intrinsic catalysts for the transamination of vinylogous urethane and urea linkages, eliminating the need for external catalyst additives. This self-catalyzed mechanism simplifies the material composition and avoids catalyst-related discoloration issues.
Solution Approach 2:
The free amine groups in the network serve as intermediary species that facilitate the exchange reactions between vinylogous bonds. These amine groups temporarily form intermediate complexes during the transamination process, enabling bond exchange without requiring external catalysts. The amine groups are integral to the network structure and mediate the exchange reactions in situ.
3Ease of repair
If extensive heating is applied to enable recycling, then bond exchange is achieved, but energy consumption and risk of structural damage increase
Solution Approach 1:
The patent designs the vinylogous bond exchange reactions to occur at relatively low temperatures (typically above the glass transition temperature but below 200°C). This lower activation temperature requirement reduces the energy input needed for recycling compared to conventional thermosets that require much higher temperatures for bond breaking. The controlled parameter change enables recycling at energy-efficient conditions.
Solution Approach 2:
The dynamic covalent bonds in the network enable recycling through bond exchange rather than bond breaking. This dynamic mechanism allows the network to reconfigure and flow at lower temperatures compared to the thermal degradation required for conventional thermoset recycling. The process occurs below the degradation temperature, preventing structural damage while consuming less energy.
4Adaptability or versatility
If vinylogous urethane/urea/amide functions are combined with free amines, then transamination and vitrimer behavior are achieved, but manufacturing complexity increases
Solution Approach 1:
The patent combines multiple functional components (epoxide groups, vinylogous precursors, and amine groups) into an integrated curing system. The epoxide and amine groups form the primary cross-linked network, while the vinylogous precursors react with amine groups to create exchangeable vinylogous bonds. This merging of functions into a single curing process simplifies manufacturing compared to multi-step processes, despite the complexity of the resulting vitrimer behavior.
Solution Approach 2:
The amine groups in the network serve multiple functions: they form permanent cross-links with epoxide groups, catalyze bond exchange reactions, and participate in vinylogous bond formation. This multi-functionality reduces the need for separate additives or components, simplifying the manufacturing process while achieving complex vitrimer behavior with both permanent and dynamic bonds.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The epoxy-derived CANs exhibit broad application windows, low relaxation times, transparency, and reduced energy requirements for recycling, while maintaining mechanical properties and optical clarity, enabling efficient recycling and reprocessing without structural damage.
Implementation Method 1
based on the presence of a combination of vinylogous urethane (-N-C=C-C(=O)-O-), vinylogous urea (-N-C=C-C(=O)-NR'-) or vinylogous amide (-N-C=C-C(=O)-CR'R'-) functions with free amines, allowing for transamination
Implementation Method 2
low relaxation times
Implementation Method 3
thermally triggered, resulting in the thermal malleability of the network. At higher temperatures, the viscosity of vitrimers is essentially controlled by chemical exchange reactions
Data Source
Figure 1~2
Figure 3A~3B
Figure 4A~4B
AI summary
The invention relates to a composition comprising an epoxy-derived covalent adaptable network, preferably an epoxy vitrimer comprising at least one unit of formula (I). The invention further relates to a method for preparing a composition comprising an epoxy-derived covalent adaptable network by contacting at least one amine comprising primary, at least one vinylogous precursor comprising vinylogous precursor groups and at least one epoxide comprising epoxide groups whereby the number of amine groups, the number of vinylogous precursor groups and the number of epoxide groups is controlled.