Full-Color Tunable Fluorescent Polysiloxanes Driven by Structure Evolution and Aggregation From Amine–Aldehyde Reaction

Nonconventional fluorescent materials, which are nonaromatic or consist of isolated aromatic systems, have attracted extensive attention because of their aggregation-induced emission properties. The mechanism of nonconventional fluorescence remains incompletely understood, hindering the prediction and modulation of its emission color. Achieving full-color tunability in such systems, particularly within elastomers, is highly challenging. Herein, fluorescent cross-linked polysiloxanes are synthesized using aliphatic amino-terminated polysiloxane and glutaraldehyde, exhibiting full-color emission that can be continuously tuned through thermal treatments within a single material system. Thermal treatment of cross-linked polysiloxanes enables precise control over the structural evolution of fluorophores from imines to 3-(2-piperidyl)pyridinium derivatives and their aggregation states. It enables the continuous and wide-range modulation of the emission color. Additionally, the intramolecular and intermolecular charge transfers of the novel unconventional fluorophore, 3-(2-piperidyl)pyridinium derivatives, have been identified, which are of great significance for aggregation-induced bathochromic fluorescence. Prepared from all commercial chemicals, these cross-linked polysiloxanes show great potential for large-scale production and applications, especially as flexible fluorescent light-conversion layers and solvent-responsive smart materials. Furthermore, our research is expected to inspire the innovation of unconventional fluorophores in multiple dimensions.