Seamless, self-transformation of thermoplastic polyesters into vitrimers through bond exchange-triggered cross-linking.

Abstract

In this study, we demonstrate a seamless, self-transformation system of linear thermoplastic polyester into the sustainable cross-linked polymers, vitrimers. The key is the use of polyesters bearing abundant hydroxyl side groups, which is synthesized via the reaction using dithiol molecules bearing ester units and diepoxy molecules. The polymerization reaction progresses efficiently at relatively low temperature due to the click nature of the thiol-epoxy reaction, which provides the hydroxyl side groups along the polyester chain. The tin catalyst (stannous octoate) is added in the initial polymerization, and the catalyst also works to cross-link the polyesters via intermolecular transesterification bond exchange simply by heating at high temperatures. By adjusting the degrees of cross-linking, the mechanical properties as well as the thermal properties are well tuned. The bond exchange can be still activated in the final cross-linked sample, and thus the material behaves as vitrimers, exhibiting mechanical recyclability. We also demonstrate the application of a new type of hot melt adhesive, where the post-coating tuning/enhancement of adhesion strength is realized. On the whole, the present system is very simple, but proposes a new application window of bond exchange concept into self-transformation polymers. This article is protected by copyright. All rights reserved.