Color-Tunable and Stimulus-Responsive Luminescent Liquid Crystalline Polymers Fabricated by Hydrogen Bonding

Abstract

Luminescent liquid crystalline polymers (LLCPs) show extensive application potentials, such as liquid crystal displays and circularly polarized luminescence. In this work, we employ a hydrogen-bonding strategy different from the traditional covalent-bonding method to fabricate LLCPs. First, the acceptor and donor of hydrogen bonding, (4,4′-dibutanoxy tetraphenylethylene)-1-pyridine (PTPEC4) and poly­(2-vinyl terephthalic acid) (PPA), respectively, are successfully synthesized. Then, mixtures with different molar ratios (x’s) of PTPEC4 to PPA are used to prepare a series of LLCPs [denoted as PPA­(PTPEC4) x ]. The resultant LLCPs show a smectic A phase (x ≥ 0.8), a columnar nematic phase (0.6 ≤ x ≤ 0.05), and an amorphous state (x = 0.025), depending on the x value. Meanwhile, all polymers exhibit typical aggregation-induced emission behavior. More interestingly, with the variation of the PTPEC4 content, the series of LLCPs show different colors, that is, the emission peak red shifts from 510 nm (x = 1.0) to 551 nm (x = 0.025). Furthermore, because of the reversible protonation effect of the N atom of pyridine in PTPEC4 by the strong proton acid, PPA­(PTPEC4) x shows reversible color transformation. This work provides a new method to construct LLCPs with different emission colors and reversible color transformation.

Aggregation‐induced emission systems involving supramolecular assembly

“…(A) TPE moieties covalently connected to CDs and the self-inclusion complex. (B) Cationic TPE molecules included in the cavities of CB [10]. Reproduced with permission.…”

“…Similarly, CB[n]s also have been used as the "containers" for AIEgens to achieve assembly-induced emission enhancement. For instance, TPE cationic derivatives can be encapsulated into CB [10]s via host−guest interaction in two plausible modes and thus exhibited fluorescence enhancement ( Figure 5B). [36]…”

“…Wang, Xie, and coworkers demonstrated a liquid crystalline polymer assembled by hydrogen bonding named PPA(PTPEC 4 ) x (Figure 1A), which consisted of TPE derivative PTPEC 4 grafted to the side chain and showed reversible color tuning of fluorescence emission. [ 10 ] As PTPEC 4 content decreased, the emission color of the polymer in the solid state showed a red shift from 510 nm to 551 nm (Figure 1C and 1D). This phenomenon was attributed to the less restricted conformation of PTPEC 4 when less hydrogen bonds were formed within the polymer.…”

“…[9] Copyright 2019, Royal Society of Chemistry; Reproduced with permission. [10] Copyright 2019, American Chemical Society to the dynamic and directional nature of the noncovalent driving forces, supramolecular assemblies are endowed with intriguing properties, such as good reversibility and stimuli-responsiveness, whereby the assembling processes can be adjusted by varying the basic molecular modules and/or exerting external actuations. Till today, a large number of AIEgen-containing supramolecular assemblies have been reported varying from simple complexes to sophisticated supramolecular ensembles, demonstrating adjustable features in various aspects including luminescence intensities, emission colors, and assembly morphologies, which relate closely to the altered strength or binding modes of supramolecular complexation.…”

Functional Polymer Systems with Aggregation-Induced Emission and Stimuli Responses

“…The detection of gas like CO 2 and volatile organic chemicals (VOCs) such as NH 3 and acid vapor is fundamentally important for a diverse array of real-world applications. In the past years, various AIE-based polymer systems with gas/vapor responsiveness have been reported [100][101][102][103]. They are promising for use as selective CO 2 detection, monitoring of morphology transformations of nanoassemblies, detection of biogenic amines and seafood spoilage, multi-scale humidity sensing, etc.…”