Tunable Mechanical and Dynamic Properties via Cross-Linker Length in Bis(hindered amino)Disulfide-Based Covalent...

Area of Science:

• Polymer Science and Engineering
• Materials Chemistry
• Dynamic Covalent Chemistry

Background:

• Conventional cross-linked polymers lack recyclability and reprocessability due to permanent cross-links.
• Covalent adaptable networks (CANs) offer solutions with dynamic covalent chemistry, enabling stress relaxation, recyclability, reprocessability, and self-healing.
• Precise control over CAN dynamic properties is crucial for scientific advancement and practical applications.

Purpose of the Study:

• To investigate the relationship between cross-linker length and the dynamic properties of CANs.
• To understand how varying cross-linker length impacts polymer-chain mobility, reprocessing rate, and stress relaxation.
• To establish guidelines for designing CAN-based materials with tailored dynamic characteristics.

Main Methods:

• Synthesis of CANs incorporating bis(hindered amino)disulfide linkages at cross-link points with varying cross-linker lengths.
• Characterization using viscoelasticity measurements and tensile tests to assess mechanical properties and polymer-chain dynamics.
• Evaluation of reprocessing capabilities and stress relaxation behavior under different conditions.

Main Results:

• Increased cross-linker length directly correlates with enhanced polymer-chain mobility and a higher reprocessing rate.
• Stress relaxation and reprocessing tests indicate that cross-linker length influences the overall reprocessing rate but not the flow activation energy.
• Viscoelasticity and tensile tests confirm the impact of cross-linker length on material dynamics.

Conclusions:

• Cross-linker length is a critical parameter for tuning the dynamic properties of CANs.
• By adjusting cross-linker length, materials scientists can design CANs with specific reprocessing rates and mechanical responses.
• This study provides fundamental insights for developing advanced, adaptable, and recyclable polymer materials.