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

Abstract

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.

Regulation of Photophysical Behaviors in Hyperbranched Aggregation-Induced Emission Polymers for Reactive Oxygen Species Scavenging

“…Clusteroluminescence (CL) materials with nonconjugated structures and visible luminescence have aroused wide attention in sensing, biomedicine, bioimaging, etc. − Differing from traditional π-conjugated aromatic structures, CL materials that contain clustered electron-rich atoms have outstanding biocompatibility and processability and have been considered as an indispensable part of aggregation-induced emission (AIE) materials. − The CL performance of these materials can be well regulated by the clusterization-triggered emission (CTE) mechanism, which drives the formation of clustered electron-rich groups and the generation of electron delocalization. , Up to now, several CL materials have been discovered or synthesized, such as cellulose, polyester, poly­(amido amine) (PAMAM), etc. However, most of the reported CL materials suffer from small Stokes shifts, with limited emissions in the blue region.…”

Silicone-Enhanced Polyvinyl Alcohol Hydrogels with Intrinsic Photoluminescence and High Mechanical Intensity

“…Fluorescent hydrogels have traditionally been prepared by coupling or doping a hydrogel matrix with fluorescent units, such as semiconductor quantum dots, metal–ligand complexes, lanthanide ions, and organic dyes. − However, these conventional fluorescent hydrogels have inherent drawbacks, including poor photostability, high cytotoxicity, and low mechanical strength, which limit their application. Recently, the nontraditional intrinsic luminescence (NTIL) materials, which achieves fluorescence in the absence of conventional fluorescent groups, have emerged. , For example, molecules containing only amide groups, carbonyl groups, or aliphatic amines are fluorescent. − Importantly, these special luminescent materials also exhibit high photostability, biosafety, good water solubility, and degradability and can potentially be used in biomedical applications. , However, attempts to prepare fluorescent polymer hydrogels using intrinsic luminophores have been unsuccessful, which is ascribable to the lack of functional cross-linking molecules. , Furthermore, much research has also focused on improving the mechanical properties of hydrogels, including their tensile strength, toughness, and elongation at break, because these properties are critical for multidisciplinary and multifunctional applications. Several strategies have been developed to improve the mechanical properties of hydrogels, including the use of free-radical polymerized hydrogels, , nanocomposite hydrogels, , ionically cross-linked hydrogels, , polymer microsphere composite hydrogels, , and dual-network hydrogels. ,, Among them, dual-network hydrogels have received considerable attention because they can be dynamically tuned and exhibit excellent mechanical properties.…”