Luminescent core–shell nanoparticles with crosslinked aggregation‐induced emission core structures: Emission both in solution and solid states

Abstract

Luminescent core–shell nanoparticles (NPs) with crosslinked aggregation‐induced emission (AIE) core structures, which exhibited excellent emission independent of the dispersion state of the NPs, have been developed by a facile one‐pot method based on the self‐assembly of an amphiphilic block copolymer poly(PEGMA)‐b‐poly(DB3VT). Core–shell micelles with a poly(DB3VT) core were formed from poly(PEGMA)‐b‐poly(DB3VT) in tetrahydrofuran (THF)/H2O condition, and the crosslinked AIE‐based structure was selectively incorporated into the core by the Suzuki coupling reaction between poly(DB3VT) blocks and tetraphenylethylene (TPE)‐based coupling monomers at the same time. This method afforded a uniform NP with a crosslinked TPE‐based AIE core structure. The obtained NP exhibited excellent emission both in diluted solution and solid states. This result indicated that the formed TPE‐based AIE core structure was always aggregated regardless of NP dispersion owing to the crosslinking as we expected. The crosslinked TPE‐based AIE core structure, which was related to the emission property, was readily tuned by the selection and combination of coupling monomers in the Suzuki coupling reaction. By incorporating electron‐deficient units into the core, the emission color could be successfully tuned from yellow‐green to orange and red while maintaining the emission property independent of the state of the NP dispersion. These results demonstrated that NPs with the crosslinked AIE core structures are a promising luminescent material design motif to realize emission independent on molecular dispersion.

Aggregation‐induced multicolor luminescent nanoparticles with adaptive and fixed cores derived from brominated tetraphenylethene‐containing block copolymer

“…The obtained product is soluble in common organic solvents such as THF, chloroform, methanol, and water, owing to the presence of long poly(PEGMA) side chains in the amphiphilic block copolymer. In contrast to our previous study which used the Suzuki coupling reaction between the brominated thiophene unit in the assembled block copolymer and TPE‐based diboronic acid, 28 a brominated TPE‐containing amphiphilic block copolymer was developed in this study, which enables us to produce molecular state‐dependent and ‐independent luminescences with adaptive and fixed core structures.…”

“…2,5‐Thiophenediylbisboronic acid (Th‐[BOH 2 ] 2, Aldrich, ≥95.0%), 4,7‐bis(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)‐2,1,3‐benzothiadiazole (BTz‐Bpin 2 , TCI, >95.0%), 9,10‐bis(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)anthracene (An‐Bpin 2 , TCI, >98.0%), 9‐phenyl‐3,6‐bis(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)carbazole (Cz‐Bpin 2 , TCI, >98.0%), 5,10‐bis(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)naphtho[1,2‐c:5,6‐c′]bis([1,2,5]thiadiazole), (NTD‐Bpin 2 , TCI, >98.0%), 2,7‐bis(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)‐9,9‐dimethylfluorene (DFL‐Bpin 2 , TCI, >98.0%), 4,7‐dibromo‐2,1,3‐benzothiadiazole (BTz‐Br 2 , TCI, >98.0%), 2,7‐dibromofluorene (FL‐Br 2 , TCI, >98.0%), 4,4′‐dibromotriphenylamine (TPA‐Br 2 , TCI, >98.0%), 2,7‐dibromo‐9,9‐dimethylfluorene (DFL‐Br 2 , TCI, >98.0%) were used as received. 1,2‐Diphenyl‐1,2‐bis[4‐(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)phenyl]ethane (TPE‐Bpin 2 ) was synthesized as reported previously 28 …”

“…Crosslinking has frequently been applied as a strategy for achieving stable AIE‐active and fluorescent polymeric NPs and assembled materials. For example, we previously reported a facile one‐pot synthesis of NPs with crosslinked TPE cores by the self‐assembly of an amphiphilic block copolymer consisting of a dibromo‐substituted‐vinylthiophene and poly(ethylene glycol) ethyl ester methacrylate (PEGMA), as well as the Suzuki coupling reaction of TPE‐based diboronic acid 28 . Owing to the crosslinked (fixed) core structure, the resulting core–shell NPs displayed excellent emission in solution and solid states, independent of the dispersion state.…”

“…For example, we previously reported a facile one-pot synthesis of NPs with crosslinked TPE cores by the self-assembly of an amphiphilic block copolymer consisting of a dibromosubstituted-vinylthiophene and poly(ethylene glycol) ethyl ester methacrylate (PEGMA), as well as the Suzuki coupling reaction of TPE-based diboronic acid. 28 Owing to the crosslinked (fixed) core structure, the resulting core-shell NPs displayed excellent emission in solution and solid states, independent of the dispersion state. Hadjichristidis et al, synthesized crosslinked multiarm star polymers with an AIE core, exhibiting emission both in solution and solid states, by a so-called arm-first method using a double styrene-functionalized TPE as a crosslinker.…”

“…1,2-Diphenyl-1,2-bis[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl) phenyl]ethane (TPE-Bpin 2 ) was synthesized as reported previously. 28…”