Molecular Motions in Polymer Matrix for Microenvironment Sensing

Polymer science entails the structural study at multi-levels from nano- to micro- and mesoscale, which is highly important to transfer or even amplify the molecular information to macroscopic materials. Multiple polymer structural transitions from lower-order to higher-order superstructures are normally involved to achieve selective, efficient and sophisticated functions. Therefore, in-situ visualization of these processes is highly important, not only for fundamental understanding the structural evolution, but also for the optimization of the process flow during the materials processing. Fluorescence imaging based on aggregation-induced emission(AIE) provides an ideal tool that offers a simple, accurate, and easy-readable method to fulfill the above requirements. Owing to the twisted propeller-like structure of AIE luminogens(AIEgens), they show high fluorescence sensitivity to the surrounding microenvironment(e.g., viscosity, rigidity, and polarity) through intramolecular motions. In this short review, we summarize the recent applications of AIEgens to serve as “built-in” sensors to analyze the process of polymerization, microphase separation, glass/vitrification transition, polymer solvation, crystallization, etc. The perspective on the future application of AIE technology in polymer engineering, especially fiber materials, is also discussed.