Vitrimers are one kind of covalently crosslinked polymers that can be reprocessed. Topology freezing transition temperature (T_v) 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_v 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_v, providing an accurate method to measure T_v without the interference of external force. Moreover, according to this method, T_v 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.

The osmotic energy, a large-scale clean energy source, can be converted to electricity directly by ion-selective membranes. None of the previously reported membranes meets all the crucial demands of ultrahigh power density, excellent mechanical stability, and upscaled fabrication. Here, we demonstrate a large-scale, robust mushroom-shaped (with stem and cap) nanochannel array membrane with an ultrathin selective layer and ultrahigh pore density, generating the power density up to 22.4 W·m⁻² at a 500-fold salinity gradient, which is the highest value among those of upscaled membranes. The stem parts are a negative-charged one-dimensional (1D) nanochannel array with a density of ~10¹¹ cm⁻², deriving from a block copolymer self-assembly; while the cap parts, as the selective layer, are formed by chemically grafted single-molecule–layer hyperbranched polyethyleneimine equivalent to tens of 1D nanochannels per stem. The membrane design strategy provides a promising approach for large-scale osmotic energy conversion.