Force-dependent bond dissociation explains the rate-dependent fracture of vitrimers

TL;DR

This study reveals that the rate-dependent fracture behavior of vitrimers is governed by force-dependent bond dissociation, with intrinsic fracture energy varying significantly with tear speed, explained by Eyring theory.

Contribution

First experimental quantification of intrinsic fracture energy and bulk dissipation in vitrimers, linking rate dependence to bond exchange reactions.

Findings

Intrinsic fracture energy depends strongly on tear speed.

Bulk dissipation shows weak dependence on tear speed.

Force sensitivity of covalent bonds explains rate-dependent fracture behavior.

Abstract

We investigate the rate-dependent fracture of vitrimers by conducting a tear test. Based on the relationship between the frac-ture energy and the thickness of vitrimer films, we, for the first time, obtain the intrinsic fracture energy and bulk dissipation of vitrimers during crack extension. The intrinsic fracture energy strongly depends on tear speed, and such dependence can be well explained by Eyring theory. In contrast, the bulk dissipation only weakly depends on tear speed, which is drastically different from observations on traditional viscoelastic polymers. We ascribe such a weak rate-dependence to the strong force-sensitivity of the exchange reaction of the dynamic covalent bond in the vitrimer.