Polymeric Emissive Materials Based on Dynamic Covalent Bonds

Abstract

Dynamic covalent polymers, composed of dynamic covalent bonds (DCBs), have received increasing attention in the last decade due to their adaptive and reversible nature compared with common covalent linked polymers. Incorporating the DCBs into the polymeric material endows it with advanced performance including self-healing, shape memory property, and so forth. However, the emissive ability of such dynamic covalent polymeric materials has been rarely reviewed. Herein, this review has summarized DCBs-based emissive polymeric materials which are classified according to the different types of DCBs, including imine bond, acylhydrazone bond, boronic ester bond, dynamic C-C bond, as well as the reversible bonds based on Diels-Alder reaction and transesterification. The mechanism of chemical reactions and various stimuli-responsive behaviors of DCBs are introduced, followed by typical emissive polymers resulting from these DCBs. By taking advantage of the reversible nature of DCBs under chemical/physical stimuli, the constructed emissive polymeric materials show controllable and switchable emission. Finally, challenges and future trends in this field are briefly discussed in this review.

Keywords: dynamic covalent bond; dynamic covalent chemistry; polymeric emissive material; stimuli polymer.

Scheme 1

Dynamic covalent bond introduced in polymeric emissive materials.

Scheme 2

The three types of imine reactions: (a) imine condensation, (b) exchange, and (c) metathesis.

Figure 1

The formation of the emissive self-healing gel based on dynamic imine bonds and the luminescence mechanism in Ref. [29]. Reproduced with permission from Ref. [29]. Copyright 2019, American Chemical Society.

Figure 2

Imine-based 2D-COFs with high photoluminescence quantum yield in Ref. [38]. Reproduced with permission from Ref. [38]. Copyright 2018, Royal Society of Chemistry.

Scheme 3

The formation of acylhydrazone via reversible condensation reaction.

Figure 3

(a) Schematic diagram of chemical Rubik’s Cube (RC) preparation. (b) Chemical structures and representations of the hydrogels used in Ref. [44]. (c) Chemical structures of the AIEgens used in Ref. [44]. Reprinted with permission from Ref. [44]. Copyright 2019, Wiley-VCH.

Figure 4

Synthetic scheme for accessing the emissive COFs based on acylhydrazone bond. The photoluminescent emission maxima and bandwidths are shown for each COF from Ref. [52]. Reprinted with permission from Ref. [52]. Copyright 2018, Nature Publishing Group.

Scheme 4

Reversible break and reform of the boronic esters between boronic acids and diols.

Figure 5

(a) The formation of flower like assembly in Ref. [59]. Reproduced with permission from Ref. [59]. Copyright 2012, Royal Society of Chemistry. (b) Preparation of white-light emitting boronate assembly. Reproduced with permission from Ref. [60]. Copyright 2013, Royal Society of Chemistry. (c) A plausible partial structure where fluorescence resonance energy transfer occurs in tetraphenylethylene and rhodamine B-based assembly. (d) The fluorescence microscopic image of white-light emissive assembly in Ref. [61]. Reproduced with permission from Ref. [61]. Copyright 2015, Royal Society of Chemistry.

Figure 6

The chemical structure of (a) Py-DBA-COF 1, (b) Py-MV-DBA-COF, and (c) Py-DBA-COF 2. (d) Normalized emission spectra and photographs of Py-DBACOF 1 (orange line), Py-DBA-COF 2 (green line), and Py-MV-DBA-COF (orange dashed line), respectively. Reproduced with permission from Ref. [63]. Copyright 2016, American Chemical Society.

Scheme 5

The representative reaction formula of transesterification.

Figure 7

Schematic image of the color change mechanism of the folding fluorescent probe in (a) molecule and (c) polymer state. (b,d) are the molecular structures of the folding fluorescent probe in molecular and polymer state. Reproduced with permission from Ref. [69]. Copyright 2021, Royal Society of Chemistry.

Scheme 6

(a) The general formula of reversible Diels–Alder reaction. (b) Elevated temperature-induced reversible DA reaction between furan and maleimide derivatives. (c) Force-induced retro DA reaction between π-extended anthracene and maleimide derivatives.

Figure 8

The structures of three organic room-temperature phosphorescence polymers in Ref. [81]. Reprinted with permission from Ref. [81]. Copyright 2020, Wiley-VCH.

Figure 9

(a) Retro Diels–Alder reaction of PMA-substituted anthracene–maleimide to yield the PMA-substituted induced by mechanical force. (b) Triplet sensitizer octaethylporphyrin (PtOEP) used in Ref. [89]. (c) Jablonski diagram of the TTA-UC process in which 1 served as annihilator and emitter and 3 as the triplet photosensitizer. (d) The blue UC emission of the PHMA in solid state when swelled in a PtOEP solution. Reproduced with permission from Ref. [89]. Copyright 2019, Wiley-VCH.

Scheme 7

(a) Schematic representation of reversible dynamic C-C bond. The typical central radicals derived from (b) DABBF and (c) TASN.

Figure 10

(a) Photographs of PS-TASN-PS before and after grinding, and the ground sample under UV irradiation. (b) EPR spectra of PS-TASN-PS before and after grinding. (c) Chemical structure of radical species derived from PS-TASN-PS. Reproduced with permission from Ref. [95]. Copyright 2022, Royal Society of Chemistry.