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Using Nanosphere Embedding to Probe the Surface and Bulk Relaxation in Vitrimers
Hongkun Yang1, Kaili Hu1, Dong Wang1
1State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029, China.
Summary
Vitrimers exhibit dynamic relaxation crucial for self-healing and welding. This study reveals significantly faster surface relaxation in epoxy-based vitrimers compared to bulk, aiding material processing.
Area of Science:
- Materials Science
- Polymer Chemistry
- Surface Science
Background:
- Vitrimers possess a dynamic network structure governed by associative chemical exchange reactions.
- This dynamic behavior is critical for applications like self-healing, welding, and reprocessing.
- Understanding relaxation dynamics at different length scales is key to optimizing vitrimer performance.
Purpose of the Study:
- To investigate the surface and bulk relaxation behavior of epoxy-based vitrimers.
- To quantify the difference in relaxation dynamics between the surface and the bulk.
- To elucidate the mechanisms influencing surface relaxation.
Main Methods:
- Utilized atomic force microscopy (AFM) to image the embedding of gold nanospheres into epoxy-based vitrimers.
- Assessed surface and bulk relaxation by observing nanosphere indentation.
- Estimated activation energies for relaxation at both surface and bulk regions.
Main Results:
- Gold nanospheres were observed to embed into vitrimers even at temperatures well below the bulk topology freezing transition temperature.
- Surface relaxation was found to be significantly faster than bulk relaxation, indicated by lower activation energy.
- The enhanced surface relaxation is attributed to network defects and reduced intermolecular exchanges.
Conclusions:
- Vitrimers exhibit distinct surface and bulk relaxation behaviors.
- Surface relaxation is considerably more facile than bulk relaxation, offering processing advantages.
- Network defects and reduced intermolecular exchanges accelerate surface relaxation in vitrimers.
