Fused Heterocyclic Polymers with Aggregation-Induced Emission: Synthesis and Applications

Abstract

Fused heterocyclic polymers with aggregation-induced emission (AIE) have attracted much attention due to their unique photoelectric properties, efficient aggregate-state fluorescence, high thermal stability, and superamplification effect as fluorescence sensors as well as multiple functionalities. Among various synthetic methodologies toward fused heterocyclic AIE polymers, polymerization based on triple bond-containing monomers such as alkynes and (iso)­cyanides is a powerful synthesis tool that can in situ generate fused heterocyclic units in polymer backbones in high efficiency. In this Review, we summarize the recent progress in the synthesis of nitrogen-, oxygen-, and multiple heteroatom-containing fused cyclic polymers with AIE features based on polymerizations of triple bond-containing monomers. Furthermore, the high-tech applications of the corresponding fused heterocyclic AIE polymers in the visualization of morphological structures, fluorescence chemo-sensors, stimuli-responsive materials, and photodynamic therapy are illustrated. Finally, perspectives on the challenges and future development directions of this field are discussed.

Tuning Photophysical Properties via Positional Isomerization of the Pyridine Ring in Donor–Acceptor-Structured Aggregation-Induced Emission Luminogens Based on Phenylmethylene Pyridineacetonitrile Derivatives

“…A series of organometallic or coordination AIEgens have been synthesized as mechanochromic luminescence (MCL) materials with better photophysical properties, richer emission colors, and more controllable MCL effects [ 25 ]. AIE polymers characterized by fused heterocyclic building blocks were also developed for the practical application of morphological structure visualization (e.g., microphase separation of polymer blends) and external stimuli response [ 26 ]. These research efforts have paved the way for the development of AIE-based optoelectronic devices, yet the synthetic complexity and material cost (such as the molecules containing noble metals) are currently the limitations for the broader applications of these AIEgens.…”

Aggregation-Induced Emission of Contorted Polycondensed Aromatic Hydrocarbons Made by Edge Extension Using a Palladium-Catalyzed Cyclopentannulation Reaction

“…Such quenching of the emission intensity is known as “aggregation caused quenching (ACQ)” effect, which is an intractable challenge for optoelectronic devices . In 2001, Tang et al reported the synthesis of new organic compounds whose emission is only enhanced upon aggregation coining this photophysical phenomenon as aggregation-induced emission (AIE), thus allowing for the development of various small molecules and polymers for various applications, among others, photonics, nuclear and particle physics, quantum electronics, and medical diagnostics. − While the mechanism behind the AIE phenomenon is still debated, most research focuses on the synthesis of organic molecules with rotation axes and whose restricted intramolecular rotation (RIR) caused by aggregation leads to AIE . Additionally, other materials have been developed revealing AIE behavior but whose mechanisms are based on the restriction of intramolecular charge transfer (ICT), twisted intramolecular charge transfer (TICT), cis – trans isomerization, planarization, J-type aggregates, etc. − …”

1+1>2: Fiber Synergy in Aggregation‐Induced Emission

“…Therefore, it becomes increasingly important to manipulate aggregates for transferring or even amplifying the molecular information to macroscopic properties for advanced applications. [14] At the aggregate state, AIEgens are interacted through diverse intermolecular interactions at the mesoscale, their packing modes, [15] compositional and morphological structures, [16] supramolecular structures [17] and molecular motions [18] could be manipulated for desired optical properties. Due to the molecular flexibility and rotor structure, the aggregate structure of AIEgens is highly sensitive to the surrounding environment (e. g., polarity, [19] viscosity, [20] crystallinity, [15b] rigidity [21] ), resulting in adjustable optical signals.…”