Introduction of Photolatent Bases for Locally Controlling Dynamic Exchange Reactions in Thermo‐Activated Vitrimers

TLDR

Vitrimers are covalently crosslinked polymers that can rearrange their network topology through thermo‑activated associative exchange reactions above a topology‑freezing temperature, yet spatially controlled initiation of these rearrangements remains largely unavailable. The study aims to demonstrate localized release of the transesterification catalyst TBD via UV‑induced cleavage of a photolatent base in a thiol–epoxy vitrimer network. By incorporating a photolatent base that cleaves under UV light, the authors trigger the release of TBD, which then catalyzes transesterification within the crosslinked network. Stress‑relaxation experiments above Tv confirm that controlled TBD release induces immediate transesterification and viscoelastic flow, while UV‑mediated activation produces localized permanent shape changes.

Abstract

Abstract Vitrimers exhibit a covalently crosslinked network structure, as is characteristic of classic thermosetting polymers. However, they are capable of rearranging their network topology by thermo‐activated associative exchange reactions when the topology freezing transition temperature (T v ) is exceeded. Despite the vast number of developed vitrimers, there is a serious lack of methods that enable a (spatially) controlled onset of these rearrangement reactions above T v . Herein, we highlight the localized release of the efficient transesterification catalyst 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene (TBD) by the UV‐induced cleavage of a photolatent base within a covalently crosslinked thiol–epoxy network. Demonstrated with stress relaxation measurements conducted well above the network's T v , only the controlled release of TBD facilitates the immediate onset of transesterification in terms of a viscoelastic flow. Moreover, the spatially resolved UV‐mediated photoactivation of vitrimeric properties is confirmed by permanent shape changes induced locally in the material.