Cross-linkable End-cappers for Polyimides
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Solution Overview
Problem
Current cross-linking technologies for polyimides, such as phenylethynyl terminated imide oligomers (PETIs), require high curing temperatures, which can be impractical for certain applications and lead to inferior thermal stability due to the use of moieties like phenylethynyl phtalic anhydride (PEPA) or ethynyl phtalic anhydride (EPA), which have drawbacks in reaction pathways and manufacturing complexity.
Innovation Solution
Development of compounds according to formula (I) or (II), featuring aryl or heteroaryl groups with specific substituents, which act as cross-linkable end-cappers for oligo- and polyimides, allowing for cross-linking at significantly lower temperatures, such as around 250°C, without oxidative degradation, and are more versatile in solvent compatibility and synthesis simplicity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If phenylethynyl terminated imide oligomers (PETIs) are used for cross-linking, then mechanical strength and heat resistance are improved, but curing temperature becomes too high (above 350°C) for practical processing
Solution Approach 1:
The patent modifies the molecular structure of the cross-linker by changing the substituent on the ethynyl group from phenylethynyl (PEPA) to ethynyl (EPA). This structural parameter change reduces the curing temperature from above 350°C to around 250°C, making the material processable while maintaining cross-linking benefits
Solution Approach 2:
The patent uses a simpler, more readily available cross-linker (EPA instead of PEPA) that achieves the same cross-linking function at lower cost and with easier processing. The ethynyl group is simpler to incorporate and requires no protective group chemistry, making it a more practical choice despite the lower curing temperature requirement
2Strength
If phenylethynyl phtalic anhydride (PEPA) is used as cross-linker, then cross-linking is achieved, but thermal stability deteriorates due to oxidative degradation above 200°C
Solution Approach 1:
The patent replaces PEPA with EPA, which has inferior thermal stability but is compensated by the fact that it enables cross-linking at lower temperatures. The simpler ethynyl group avoids the oxidative degradation issues of PEPA when used in the appropriate temperature range
Solution Approach 2:
The patent introduces a sulfur promoter as an intermediary substance that facilitates cross-linking at lower temperatures. The sulfur promoter mediates the reaction between ethynyl groups, enabling cross-linking below 200°C without requiring the thermally unstable PEPA cross-linker
3Temperature
If ethynyl phtalic anhydride (EPA) is used as cross-linker, then curing temperature is reduced to around 250°C, but chain extension reaction pathways are favored over desired cross-linking
Solution Approach 1:
The patent introduces a sulfur promoter as an intermediary that selectively promotes cross-linking reactions over chain extension. The sulfur promoter mediates the reaction between ethynyl groups to form cross-linked structures, suppressing alternative reaction pathways that would lead to chain extension
Solution Approach 2:
The patent modifies the reaction conditions by adding a sulfur promoter, which changes the reaction pathway selectivity. This parameter change (adding sulfur promoter) ensures that the desired cross-linking reaction is favored over chain extension when using EPA as the cross-linker
4Strength
If high curing temperature (above 350°C) is used for PETI cross-linking, then mechanical properties are improved, but processability deteriorates due to high viscosity and melting issues
Solution Approach 1:
The patent changes the cross-linker from PEPA to EPA, which fundamentally alters the curing temperature parameter from above 350°C to around 250°C. This parameter change enables the material to be processed at lower temperatures, improving processability while maintaining mechanical properties through effective cross-linking
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
These compounds enable effective cross-linking of oligo- and polyimides at lower temperatures than traditional methods, improving thermal stability and mechanical strength while simplifying the manufacturing process, and are suitable for use in a variety of solvents, making them a more practical alternative for applications like aerospace and electronics.
Implementation Method 1
the polymer chains are cross-linked, they may be shorter whilst the mechanical properties are maintained or even improved
Data Source
AI summary
Disclosed are novel cross-linkable end-cappers for oligo- and polyimides. End-capped oligo- and polyimides comprising such an end-capper may be cured at a lower temperature compared to oligo- and polyimides end-capped with PEPA.