Synthesis of amorphous lowT_gpolyesters with multiple COOH side groups and their utilization for elastomeric vitrimers based on post-polymerization cross-linking

Abstract

Elastomeric vitrimer materials with tunable cross-link densities are prepared using cross-linking precursor polyesters with multiple COOH side groups in the presence of diepoxy cross-linkers and trans-esterification catalysts.

Elasticity and Relaxation in Full and Partial Vitrimer Networks

“…This stress decays with time in the simple-exponential form, which is the key characteristic of a vitrimer possessing a unique energy barrier for the chain exchanging (as opposed to a physically bonded transient network, where the broad distribution of the energy barrier for the crosslink breakage leads to a slower stretched-exponential decay 30,47,48 ). However, vitrimers could also exhibit a stretched exponential stress relaxation: the bond-exchange rate may have a distribution due to a tensile force dependence of the connecting two crosslinks.…”

Vitrimers: directing chemical reactivity to control material properties

“…7b), 51 as also observed by Hayashi and co-workers. 64 However, in all these studies the change in cross-link density was accompanied by a modication of the concentration of reactive/exchangeable groups. Therefore, the establishment of a clear correlation between cross-link density and vitrimer properties, without considering other network parameters, is not possible.…”

“…59 Nonetheless, in a similar case study dealing with polyesters, COOH side groups were crosslinked by di-epoxy compound and the opposite phenomenon was reported. 64 Indeed, Hayashi and coworkers observed the fastest relaxation rate for the highest cross-link density. It is important to keep in mind that despite the use of comparable network architectures, different exchange mechanisms were involved (boronic ester metathesis vs. transesterication).…”

“…Very recently, Hayashi and co-workers examined this aspect based on an already reported polyester vitrimer material. 64 By using mono-and difunctional epoxy groups, the authors were able to prepare polyester based vitrimers with varying cross-link density while keeping the concentration of reactive hydroxyl groups constant. 65 Similar trends were observed in comparison to their rst study, although to a much lesser extent (Fig.…”

Implantation of Recyclability and Healability into Cross-Linked Commercial Polymers by Applying the Vitrimer Concept

“…In this section, the basic physical properties of vitrimers are demonstrated on the basis of the report from M. Hayashi et al for trans-esterification-based vitrimers (see the molecular design in Figure 4) [26]. In their report, vitrimer samples were prepared by cross-linking the low T g amorphous polyesters bearing multiple COOH side groups (PE-COOH) with di-epoxy cross-linkers.…”