Aggregation-Induced Emission Properties in Fully π-Conjugated Polymers, Dendrimers, and Oligomers

Abstract

Aggregation-Induced Emission (AIE) in organic molecules has recently attracted the attention of the scientific community because of their potential applications in different fields. Compared to small molecules, little attention has been paid to polymers and oligomers that exhibit AIE, despite having excellent properties such as high emission efficiency in aggregate and solid states, signal amplification effect, good processability and the availability of multiple functionalization sites. In addition to these features, if the molecular structure is fully conjugated, intramolecular electronic interactions between the composing chromophores may appear, thus giving rise to a wealth of new photophysical properties. In this review, we focus on selected fully conjugated oligomers, dendrimers and polymers, and briefly summarize their synthetic routes, fluorescence properties and potential applications. An exhaustive comparison between spectroscopic results in solution and aggregates or in solid state has been collected in almost all examples, and an opinion on the future direction of the field is briefly stated.

Molecular Encapsulation of Naphthalene Diimide (NDI) Based π‐Conjugated Polymers: A Tool for Understanding Photoluminescence

“…[49] Crucially however, in virtually every example of conjugated polymers AIEE-specific groups (such as vinylenes or TPEs), that are well known to imbue AIEE-like properties, are introduced for this reason. [50][51][52][53][54][55] There are almost no examples of a "conventional" conjugated polymer undergoing aggregation induced enhanced emission. Moreover, it is remarkable that it has not been previously observed in P(NDI-2OD-T), which have been extensively studied.…”

Review on recent trends and prospects in π‐conjugated luminescent aggregates for biomedical applications

“…In contrast to supramolecular architecture, oligomers are low molecular weight intermediates between the monomers and polymers comprising of a few small or identical number of repeating units, whose molecular properties are proficiently dependent on the chain length. [ 65,66 ] The molecular weight of oligomers should be in the range of <10 kDa. The structure of the oligomers can be linear or star‐shaped based on their appended conjugated chain length substituted into the aromatic core, that is, the repeating units in the continuous form result in linear structure, whereas if the repeating unit is located around the central core, it leads to star‐shaped structure.…”

“…In this section, the structure–property relationships of the AIEgenic oligomers (linear and star‐shaped) (Figure 6A), [ 63–65 ] along with their distinct luminescence properties, supramolecular self‐assembly behaviors in aggregated or solid states are presented. Further, the various design strategies to develop and manipulate potentially novel AIEgenic oligomers from well‐known ACQ fluorophores are also discussed.…”

Fluorescent Polymers Conspectus

“…In comparison with traditional FPs, AIE polymers present the advantages of high PL efficiency in aggregate and solid states, a large Stokes shift, outstanding photostability, etc. Thus, AIE polymers are expected to exhibit unique properties and remarkable advantages in their practical applications [ 51 , 59 , 60 ]. Furthermore, the structure, composition, and morphology of AIE polymers can be fine-tuned to meet the diverse needs of practical applications in chemo/biosensing, imaging, and theranostics.…”