Facile Multicomponent Polymerizations toward Unconventional Luminescent Polymers with Readily Openable Small Heterocycles

Abstract

Heterocyclic polymers have gained enormous attention for their unique functionalities and wide applications. In contrast with the well-studied polymer systems with five- or six-membered heterocycles, functional polymers with readily openable small-ring heterocycles have rarely been explored due to their large synthetic difficulty. Herein, a facile one-pot multicomponent polymerization to such polymers is developed. A series of functional polymers with multisubstituted and heteroatom-rich azetidine frameworks are efficiently generated at room temperature in high atom economy from handy monomers. The four-membered azetidine rings in the polymer skeletons can be easily transformed into amide and amidine moieties via a fast and efficient acid-mediated ring-opening reaction, producing brand-new polymeric materials with distinctive properties. All the as-prepared azetidine-containing polymers exhibit intrinsic visible luminescence in the solid state under long-wavelength UV irradiation even without conventionally conjugated structures. Such unconventional luminescence is attributed to the clusteroluminogens formed by through-space electronic interactions of heteroatoms and phenyl rings. All the obtained polymers show excellent optical transparency, high and tunable refractive indices, low optical dispersions and good photopatternability, which make them promising materials in various advanced electronic and optoelectronic devices. The ring-opened polymers can also function as a lysosome-specific fluorescent probe in biological imaging.

Aggregate Science: From Structures to Properties

“…Nonconjugated luminogens that exhibit a clusterization-triggered emission (CTE) effect, known as clusteroluminogens, have recently emerged as new frontier of photonics. [188][189][190][191][192][193][194][195][196][197][198] Clusteroluminogens, including nonconjugated polymers, small molecules and metal clusters, are often nonluminescent as molecular species. [199] As shown in Figure 11A, the isolated molecules possess a large energy gap (∆E 1 ) due to the lack of through-bond conjugation resulting in ∆E 1 always corresponding to an ultraviolet emission that is weak in intensity, and invisible in wavelength to the eye, and may even be below the detection limit of spectrophotometers.…”

Through-Space Conjugation: A Thriving Alternative for Optoelectronic Materials

“…The efficient through-space conjugation formed among closelyaligned, electron-rich aromatic rings and heteroatoms in crystals is rationalized to account for the interesting AIE effect and strong solid-state emission. Along with these interesting discoveries, a new concept of clusteroluminogen 28,29 is proposed and has drawn considerable attention. As illustrated in Figure 2b, strong through-space conjugation and multiple lone-pair electronic interactions within a single molecule enable formation of a through-space conjugated luminescent material.…”

The Marriage of Aggregation‐Induced Emission with Polymer Science

“…D) Confocal images of HeLa cells stained with ring‐opened polymer. Reproduced with permission . Copyright 2018, American Chemical Society.…”

“…Recently, a facile one‐pot three‐component polymerization of diynes, disulfonyl azides, and carbodiimides was developed to synthesize functional polymers with readily openable small‐ring heterocycles (Figure C) . When TPE‐containing diyne was used as monomer, AIE polymers with multisubstituted and heteroatom‐rich azetidine frameworks could be obtained at room temperature in high atom economy.…”