Spiropyran-Doped Thiol-Yne Elastomers for Strain-Rate Sensing
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Solution Overview
Problem
Current mechanophores used in polymer materials lack strain rate-dependent mechanochromism and strain-induced crystallization properties, limiting their application in sensor and shape-memory technologies.
Innovation Solution
Development of thiol-yne-derived stereoelastomers doped with a dipropiolate-derivatized spiropyran (SP) mechanophore, which exhibits strain rate-dependent mechanochromism and strain-induced crystallization, allowing for recyclable and reusable strain-sensing and shape-memory applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional mechanophores are used in polymer materials, then basic mechanochromism is achieved, but strain rate-dependent mechanochromism and strain-induced crystallization properties are lacking
Solution Approach 1:
The patent creates a composite material system combining thiol-yne-derived stereoelastomers with spiropyran mechanophores. The stereoelastomer matrix provides strain-induced crystallization capability while the spiropyran dopant delivers mechanochromism. This composite approach enables both strain rate-dependent mechanochromism and strain-induced crystallization properties that neither component possesses alone, resolving the contradiction between adaptability and functional reliability.
Solution Approach 2:
The patent introduces spiropyran mechanophores as localized functional units within the polymer matrix at specific doping concentrations (0.1-10 wt%). These local mechanophore sites provide strain rate-dependent mechanochromism without compromising the bulk strain-induced crystallization behavior. The localized quality approach allows the material to exhibit multiple functions simultaneously, improving adaptability while maintaining reliability.
2Adaptability or versatility
If spiropyran mechanophores are doped into thiol-yne elastomers, then strain rate-dependent mechanochromism is achieved, but mechanical and thermal properties may deteriorate
Solution Approach 1:
The patent employs partial doping of spiropyran mechanophores at optimized concentrations (0.1-10 wt%, preferably 0.5-5 wt%). This partial action approach introduces sufficient mechanochromism functionality while keeping the dopant concentration low enough to preserve the mechanical strength and thermal properties of the thiol-yne elastomer matrix. The excessive doping that would compromise strength is avoided through careful concentration control.
Solution Approach 2:
The patent systematically varies the doping concentration parameter to optimize the balance between mechanochromism functionality and mechanical/thermal property preservation. By changing this parameter within specific ranges, the material achieves adequate mechanochromic response while maintaining structural integrity. This parameter optimization resolves the contradiction between gaining adaptability and preserving strength.
3Reliability
If high cis-content stereoelastomers are synthesized, then strain-induced crystallization is enhanced, but processing complexity increases
Solution Approach 1:
The patent replaces complex mechanical processing methods with a chemical approach using base-catalyzed Michael addition polymerization. This chemistry-based method allows precise control over cis-content (80-95%) through reaction conditions rather than mechanical processing. The substitution of mechanical processing with chemical synthesis simplifies the overall process while achieving the desired high cis-content for enhanced strain-induced crystallization.
Solution Approach 2:
The patent controls the cis-content parameter (80-95%) through adjustment of polymerization reaction conditions including base catalyst selection, solvent polarity, and temperature. By changing these chemical parameters during synthesis, the material achieves high cis-content for improved strain-induced crystallization without requiring complex post-processing mechanical operations. This parameter control during synthesis resolves the contradiction between reliability and processing complexity.
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 SP-doped thiol-yne elastomers display unprecedented strain rate-dependent mechanophore activation and multi-regime mechanochromism, correlating with macroscopic strain hardening and crystallization behaviors, enabling effective strain sensing and shape-memory functions while maintaining mechanical and thermal properties similar to undoped controls.
Implementation Method 1
mechanophores are force-coupled molecular switches that areomerize between two states with distinct spectroscopic properties. For example, the widely-used spiropyran (SP) mechanophore is initially colorless because of its spirocyclic structure. With applied force, SP undergoes an electrocyclic ring-opening to merocyanine (MC), and this isomerization results in a visibly observable blue or purple color
Implementation Method 2
at large deformations, the alignment of highly stretched polymer chains can lead to strain-induced crystallization (SIC). SIC results in significant material toughening due to interchain van der Waals interactions
Implementation Method 3
Eventually, this gradual transition is accompanied by strain hardening (SH). At the molecular level, SH marks the transition from a reduction in conformational entropy, to an increase in the enthalpic distortion of chemical bonds. At the polymer chain level, this corresponds to large tensile forces within the individual chains
Implementation Method 4
a base-directed Michael addition step-growth polymerization. The relative stereochemistry of the resulting alkene backbone is determined by the polarity of the solvent, which influences the coordination of the base catalyst (and thus the equilibrium constant, Keq) with the activated alkyne
Data Source
AI summary
In various embodiments. the present invention relates to a recyclable, semi-crystalline, mechanochromic elastomeric composition for use in sensor, strain-sensing and shape-memory applications having mechanochromism, SH, and SIC properties that are each strain rate-dependent. In various embodiments, the present invention is directed to a dipropiolate-derivatized spiropyran (SP) mechanophore and thiol-yne-derived stereoelastomers doped with these SP mechanophores. These SP doped, thiol-yne-derived stereoelastomers may be synthesized via a base-directed Michael addition polymerization reaction. These linear polymers have been found to be semi-crystalline, recyclable, and mechanochromic under several methods of mechanical activation.