Detecting topology freezing transition temperature of vitrimers by AIE luminogens.

Vitrimers are one kind of covalently crosslinked polymers that can be reprocessed. Topology freezing transition temperature (T) is vitrimer's upper limit temperature for service and lower temperature for recycle. However, there has been no proper method to detect the intrinsic T till now. Even worse, current testing methods may lead to a misunderstanding of vitrimers. Here we provide a sensitive and universal method by doping or swelling aggregation-induced-emission (AIE) luminogens into vitrimers. The fluorescence of AIE-luminogens changes dramatically below and over T, providing an accurate method to measure T without the interference of external force. Moreover, according to this method, T is independent of catalyst loading. The opposite idea has been kept for a long time. This method not only is helpful for the practical application of vitrimers so as to reduce white wastes, but also may facilitate deep understanding of vitrimers and further development of functional polymer materials.