Inorganic Chemistry

Cross-Linker Control of Vitrimer Flow



Vitrimers are a class of covalent adaptable networks (CANs) that undergo topology reconfiguration via associative exchange reactions, enabling reprocessing at elevated temperatures. Here, we show that cross-linker reactivity represents an additional design parameter to tune stress relaxation rates in vitrimers. Guided by calculated activation barriers, we prepared a series of cross-linkers with varying reactivity for the conjugate addition—elimination of thiols in a PDMS vitrimer. Surprisingly, despite a wide range of stress relaxation rates, we observe that the flow activation energy of the bulk material is independent of the cross-linker structure. Superposition of storage and loss moduli from frequency sweeps can be performed for different cross-linkers, indicating the same exchange mechanism. We show that we can mix different cross-linkers in a single material in order to further modulate the stress relaxation behavior.


Thumbnail image of ElZaatari Chemrxiv MS draft 2 updated.pdf

Supplementary material

Thumbnail image of TOC 12-24-2019.tiff
TOC 12-24-2019
Thumbnail image of SI 02-11-2020 BME pdf.pdf
SI 02-11-2020 BME pdf