Dynamic Polycyanurate Networks for Closed-Loop Thermoset Recycling
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Solution Overview
Problem
Existing thermoset polymers, such as polycyanurate networks (PCNs), are non-recyclable and non-malleable due to irreversible crosslinking, limiting their reuse and remolding, and current methods for recycling them are inefficient, especially for alkyl-linked variants.
Innovation Solution
Employing reversible nucleophilic aromatic substitution (SNAr) chemistry to form C—O bonds instead of traditional irreversible cyclotrimerization, allowing for the synthesis of alkyl- and aryl-linked PCNs that can be converted back to monomers for closed-loop recycling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional irreversible cyclotrimerization is used to form PCNs, then the polymer network achieves high thermal stability and structural integrity, but the material becomes non-recyclable and non-malleable
Solution Approach 1:
The patent applies dynamic reversible chemistry by replacing irreversible cyclotrimerization with reversible nucleophilic aromatic substitution (SNAr) reactions. The C-O bonds formed through SNAr can dynamically break and reform under specific conditions (presence of nucleophiles like alcohols or water), enabling the crosslinked network to transition between gel and sol states. This dynamic behavior allows the material to be remolded, repaired, and recycled while maintaining thermal stability during service conditions.
2Strength
If irreversible crosslinking is used to create thermoset polymers, then the material achieves high strength and durability, but it becomes non-processable and difficult to repair
Solution Approach 1:
The patent introduces dynamic reversibility into the crosslinked network through SNAr chemistry. The C-O crosslinks remain stable under service conditions providing durability, but can be reversibly broken by adding nucleophiles (alcohols, water) or through heating, allowing the material to be reprocessed, repaired, or reshaped. This dynamic switching between stable and reversible states resolves the contradiction between strength and processability.
3Loss of substance
If conventional recycling methods are used for PCNs, then some degradation products can be obtained, but the process is inefficient and does not achieve closed-loop recycling
Solution Approach 1:
The patent enables self-service recycling by designing the crosslinked network to automatically revert to its monomeric building blocks through reversible SNAr chemistry. When exposed to nucleophiles or heat, the C-O bonds break and release the original monomers (cyanurates and phenols) in high purity, which can be directly reused for new polymer synthesis. This self-reversing mechanism achieves efficient closed-loop recycling without requiring complex external processing.
4Productivity
If alkyl-O-C≡N monomers undergo conventional trimerization, then polymerization occurs, but the reaction is irreversible and alkyl groups are uncontrollably introduced leading to brittleness
Solution Approach 1:
The patent changes the chemical reaction mechanism from irreversible cyclotrimerization to reversible nucleophilic aromatic substitution. This parameter change in reaction chemistry allows precise control over the polymerization process. The SNAr reaction proceeds under milder conditions with better control over monomer incorporation, preventing uncontrollable alkyl group introduction and reducing brittleness while maintaining high polymerization efficiency.
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 new synthetic route enables the production of recyclable and malleable PCNs with excellent film properties and chemical resistance, facilitating the selective degradation of end-of-life PCNs into reusable monomers for repolymerization, thus promoting a circular economy.
Implementation Method 1
Employing reversible nucleophilic aromatic substitution (SNAr) chemistry to form C—O bonds instead of traditional irreversible cyclotrimerization
Implementation Method 2
allowing for the synthesis of alkyl- and aryl-linked PCNs that can be converted back to monomers for closed-loop recycling
Data Source
AI summary
The invention disclosed herein relates a novel class of alkyl- and/or aryl-linked crosslinked polymeric polycyanurate compounds and their methods of synthesis from alkoxy substituted triazines by reacting said alkoxy substituted triazines with diols. Further provided a method of synthesis of an alkyl-linked polyarylether monomer/network comprising reacting the alkoxy substituted phenyl derivatives having electron withdrawing group, with diols.