Supramolecular Polymerizations via AIE-Active Monomers: Synthesis, Self-Assembly Mechanism Study, and Explosive Detection

Abstract

The small molecule-based supramolecular gels are a novel type of soft material and have attracted extensive research attention in the past decades, wherein the most challenging work is to look for a small molecule used as a monomer to construct uniform assemblies via multiple intermolecular interactions. Obviously, if the monomer is of a rigid or an aromatic framework and also has the ability to form supramolecular gels, the resulting polymers will have the potential to be used as optical materials, such as sensors. In this paper, TPAs-3(NC−Ph−OH) is synthesized, which is very seldomly seen being used as a monomer in supramolecular systems and is a Schiff base framework synthesized from o-hydroxybenzaldehyde and aromatic amines. Additionally, TPAs-3(NC−Ph−OH) is a typical aggregationinduced emission (AIE) luminogen (AIEgen). This property endows the corresponding supramolecular polymers with more interesting optical behaviors, such as different fluorescence performances in the different states (gel and sol) and under the external stimulus (with or without external pressures). Then, we postulate the TPAs-3(NC−Ph−OH) self-assembly mechanism from different points, including single-crystal diffraction analysis, matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry, infrared (IR) spectroscopy, UV spectrum, and scanning electron microscopy (SEM) analysis. Finally, TPAs-3(NC−Ph−OH) is employed as a fluorescence sensor for the detection of explosive compound picric acid (PA), which demonstrates excellent sensitivity and selectivity for PA analysis qualitatively and quantitatively. Especially, a new way of fingerprint analysis is accomplished by TPAs-3(NC−Ph−OH) and the PA system due to the perfect on−off sensing performance.