AIE Fluorescent Gelators with Thermo‐, Mechano‐, and Vapochromic Properties

Abstract

A series of aggregation‐induced emission (AIE) fluorescent gelators (TPE‐Cn‐Chol) were synthesized by attaching tetraphenylethylene (TPE) to cholesterol through an alkyl chain. The properties of the gel, nano‐/microaggregate, and condensed phases were studied carefully. TPE‐Cn‐Chol molecules form AIE fluorescent gels in acetone and in DMF. Their fluorescence can be reversibly switched between the “on” and “off” states by a gel–sol phase transition upon thermal treatment. The AIE properties of aggregated nano‐/microstructures in acetone/water mixtures with different water fractions were studied by using fluorescence spectrometry and scanning electron microscopy (SEM). In different acetone/water mixtures, the TPE‐Cn‐Chol molecules formed different nano‐/microaggregates, such as rodlike crystallites and spherical nanoparticles that showed different fluorescence colors. Finally, the condensed phase behavior of TPE‐Cn‐Chol was studied by using polarizing microscopy (POM), differential scanning calorimetry (DSC), fluorescence spectrometry, fluorescence optical microscopy, and wide‐angle X ray scattering (WAXS). The clover‐shaped TPE unit introduced into the rodlike cholesterol mesogen inhibits not only the formation of a liquid‐crystal phase but also recrystallization upon cooling from the isotropic liquid phase. Very interestingly, TPE‐Cn‐Chol molecules in the condensed state change their fluorescence color under external stimuli, such as melting, grinding, and solvent fuming. The phase transition is the origin of these thermo‐, mechano‐, and vapochromic properties. These findings offer a simple and interesting platform for the creation of multistimuli‐responsive fluorescent sensors.

Blue-Shifting Mechanofluorochromic Luminescent Behavior of Polymer Composite Films Using Gelable Mechanoresponsive Compound

“…In particular, cholesterol can form stable gels by the synergistic effect of cooperative non-covalent bonding. Thus, vigorous research has been conducted, and application development aimed at optical function and collection performance has been explored in materials with cholesterol molecule [22]. Conversely, cholesterol has a rigid ring-fused structure and alkyl chain; therefore, it can be used as a substituent to introduce LC properties, and gelation ability can be expected without impairing the LC properties.…”

Aggregation‐Induced Emission Properties of Copper Iodide Clusters

“…[6,[20][21][22] The term piezofluorochromica ggregation-induced emission (PAIE) was even introduced. [23] Many pure organic mechanochromic materials with AIE-activem olecules were thus reported, [24][25][26][27][28][29][30][31] along with organoboron complexes. [32,33] Regarding metal-based compounds that combine AIE and mechanochromic properties, few studies have been reported, with examplesb ased on iridium(III), [34][35][36][37][38][39] cadmium(II), [40] zinc(II), [41,42] and gold(I) [43] complexes.…”

Configuration‐Dependent Liquid Crystal and Gel Behaviors of Tetraphenylethene‐Containing Main‐Chain Copolyesters

“…[ 33 ] Obviously, the better the solubility of gelator, the higher the MGC and the worse gelation ability. As mentioned in the Introduction section, the length of flexible chains [ 13,34 ] and the number of substituents [ 14,15 ] play an important role in gel behavior. From those results, we can conclude that the more regular the molecular arrangement for gelator, the more difficult it is to form gel.…”