Aggregation-induced emission polymer systems with circularly polarized luminescence

Functional materials with circularly polarized luminescence(CPL)have attracted tremendous attention due to their promising applications in three-dimensional dis-plays,chiral recognition and catalysis,photoelectronic devices,contrast imaging,information encryption,and otherfields.Among various CPL-active materials,poly-meric systems with aggregation-induced emission(AIE)have emerged as excellent candidates because of their efficient aggregate-statefluorescence,large solid-state dissymmetry factor,excellent processibility,diversified self-assembly behaviors,and readily switchable CPL properties.This review summarizes and discusses the recent progress as well as future perspective of diverse AIE polymer systems with CPL,including CPL-active covalent AIE polymers,CPL-active supramolecular AIE polymers,and AIEgen/polymer composites with CPL.According to the loca-tion or introduction method of AIEgen in polymer structures,this review further divides CPL-active covalent AIE polymers into three categories,including polymers with AIEgen in main chains,polymers with AIEgen in side chains,and CPL-active polymers with clusterization-triggered emission.CPL-active supramolecular AIE polymers are discussed based on the driving force for the formation of supramolecular polymers,including host–guest interactions,metal coordination,and other non-covalent interactions.Moreover,examples on the construction of CPL-active AIEgen/polymer composites by physically mixing AIEgens with chi-ral(supra)polymers are also presented.This review is anticipated to provide readers with an overall view on the design strategies of CPL-active AIE polymers,and facil-itate further research on the development of CPL materials and AIE polymers with advanced applications.

Aggregation-induced Emission of Non-conjugated Poly(amido amine)s:Discovering,Luminescent Mechanism Understanding and Bioapplication

It is found that the fluorescence of aliphatic poly（amido amine）s including linear and hyperbranched ones can be dramatically enhanced by simple aggregation of polymer chains, attributing to the formation of a variety of intra- and interchain clusters with shared lone-pair electrons and the restriction of intramolecular motions. Thanks to the combination of strong solid fluorescence and excellent biocompatibility, these non-conjugated polymers become promising candidates for bioimaging such as bacterial detection. This finding not only extends the aggregation-induced emission（AIE） systems from conjugated compounds to non-conjugated materials, which expands the bioapplication range of AIE systems, but also sheds light on the exploration of novel unconventional luminogens.

Multistimuli-Responsive Luminescent Porous Organic Polymers with Chiroptical Properties and Acid-Induced Degradation

Porous organic polymers(POPs)have attracted great attention in past decades.Although diverse functional POPs have been developed,multistimuli-responsive POPs with excellent aggregate-state luminescence together with good chiroptical properties have rarely been reported.Herein,two pairs of Salen-type enantiomeric PoPs with multistimuli-responsive luminescence and chiral features were designed and synthesized by facile polycondensation reactions between polyfunctional aggregation-induced emission luminogen(AlEgen)-containing salicylaldehyde derivatives and chiral diamines.With Salen units in polymer backbones as tetradentate ligands,a series of POP-metal complexes were further prepared.The obtained POPs and metal complexes show good porosity,high thermal stability,and obvious circular dichroism signals.Moreover,benefiting from the coexistence of AlEgen and Salen units in polymer structures,these POPs exhibit excellent luminescence performance in aggregate states and tunable fluorescence behaviors in response to external stimuli of Zn^(2+)ion,mechanical forces,organic solvent,and acids.Due to the dynamic feature of Schiff base C=N bonds,the present POPs can efficiently undergo hydrolysis reactions under strong acidic conditions to reproduce the AlEgencontaining monomers,and such an acid-induced degradation process can be directly visualized and dynamically monitored via fluorescence variation.These properties collectively make the POPs candidate materials for applications in heterogeneous asymmetric catalysis,fluorescence sensing,biomedicine,etc.

Highly emissive coordination polymer derived from tetraphenylethylene-tetrazole chromophore:Synthesis,characterization and piezochromic luminescent behavior

Solid-state materials that exhibit pressure stimulus-response characteristics in a manner of emission signal,known as piezochromic luminescence(PCL),demonstrate great potential in photoelectric devices.The weakened luminescence and insignificant color change in the aggregation state,however,hampers their practical applications.Herein,a highly emissive coordination polymer,[Zn2(H4TTPE)(H2O)4]·H2O(CUST-805),is successfully constructed by employing an AIE-active chromophore as the building block.The structural characterization and photophysical properties are systematically studied.Owing to intrinsic twisted conformation and AIE feature of tetraphenylethylene-tetrazole ligand,CUST-805 achieves the visible and reversible PCL from blue to green switched by different external stimuli.The transformation between crystalline and amorphous states is proved to be the origin of present PCL behavior.Moreover,on basis of electron and energy transfer quenching mechanism,the highly selective and sensitive sensor based on CUST-805 is realized,showing the low detection limit of 0.29 ppm towards 2,4,6-trinitrophenol.

Photoresponsive aggregation-induced emission polymer film for anti-counterfeiting

The development of solid-state smart materials, in particular those showing photoresponsive luminescence, is highly desirable for their cutting edge applications in displays, sensors, data-storage, and anticounterfeiting. However, to achieve both excellent photoresponsive performance and bright luminescence in solid state remains challenge. Herein, we integrate a novel photochromic fluorophore YL into flexible polymer chains, thereby enabling the resultant polymer PYL with reversible photoisomerization upon aggregation. Remarkably, the polymer PYL possesses excellent photochromic properties and aggregationinduced emission(AIE) activity, which can be attributed to the photoactive YL moiety. Upon light exposure, its film exhibits reversibly off-to-on fluorescent modulation with quick response, high emission efficiency and signal contrast, sharply different from the weak emission in solution. The novel photoresponsive AIE polymer with invisible/visible color and fluorescence transformation allows for advanced anti-counterfeiting applications. This work provides an efficient platform for constructing solid-state photocontrollable luminescent materials.

Photodegradation-Induced Turn-On Luminescence of Tetraphenylethylene-Based Trithiocarbonate Polymers

Main observation and conclusion Fluorescent intelligent materials have attracted wide attention because of their great potential applications.One major hurdle for the development and application of fluorescent intelligent materials is the aggregation-caused quenching effect in the solid state.Herein,tetraphenylethylene-based trithiocarbonate polymers with satisfactory molecular weights(Mw up to 24900)were synthesized through a one-pot polymerization route under mild conditions.The polymers were non-emissive due to the quenching effect of the trithiocarbonate group.However,upon UV irradiation,the polymers degraded and strong emission from the tetraphenylethylene unit was observed.Such a unique property endows them with great potential applications,such as photopatterning,anti-counterfeit labels,and UV detection.

Aggregation and luminescence in carbonized polymer dots

The aggregate luminescence behavior of organic luminescent materials has been studied extensively.As a new kind of luminescent nanomaterials,carbonized polymer dots(CPDs)not only inherit the stability and biocompatibility of carbon materials,but also possess the luminescence tunability,water solubility,and high photoluminescence quantum yield of organic luminescent materials,rendering them a strong candidate for the next generation of light-emitting materials.Previously,people mainly understood its luminescence from the perspective of carbon materials,but some luminescence mechanisms are still unclear.In this review,we discuss the luminescence mechanism by referring to organic luminescent materials with emphasis on their aggregation behavior.Firstly,three representative aggregate luminescence phenomena of organic luminescent materials are briefly introduced.Chromophores present in CPDs are elaborated to further discuss the potential interactions between them,with emphasis on the role of crosslinked polymer networks.On this basis,some special luminescence phenomena of CPDs in the aggregate state are summarized,and relevant mechanisms are discussed in detail to consolidate relevant statements.

Nonconventional aggregation-induced emission polysiloxanes:Structures,characteristics,and applications

Nonconventional luminescent materials have been rising stars in organic luminophores due to their intrinsic characteristics,including water-solubility,biocompatibility,and environmental friendliness and have shown potential applications in diverse fields.As an indispensable branch of nonconventional luminescent materials,polysiloxanes,which consist of electron-rich auxochromic groups,have exhibited outstanding photophysical properties due to the unique silicon atoms.The flexible Si-O bonds benefit the aggregation,and the empty 3d orbitals of Si atoms can generate coordination bonds including N→Si and O→Si,altering the electron delocalization of the material and improving the luminescent purity.Herein,we review the recent progress in luminescent polysiloxanes with different topologies and discuss the challenges and perspectives.With an emphasis on the driving force for the aggregation and the mechanism of tuned emissions,the role of Si atoms played in the nonconventional luminophores is highlighted.This review may provide new insights into the design of nonconventional luminescent materials and expand their further applications in sensing,biomedicine,lighting devices,etc.