1,8-Naphthalimide-Based Polymers Exhibiting Deep-Red Thermally Activated Delayed Fluorescence and Their Application in Ratiometric Temperature Sensing

Abstract

A series of naphthalimide (NAI)-based red-emissive thermally activated delayed fluorescence (TADF) acrylic monomers has been designed and synthesized. When copolymerized with a host material by Cu(0)-reversible deactivation radical polymerization (Cu(0)-RDRP), polymers exhibiting orange to deep-red TADF were obtained with quantum yields of up to 58% in solution and 31% in the solid state. These emitters exhibit dual emission consisting of high-energy prompt fluorescence from the NAI acceptor (λ max = 340 nm in toluene) and red-delayed fluorescence from the charge-transfer process (λ max = 633−711 nm in toluene). This dual emissive property was utilized to create redto-blue temperature-responsive polymers by copolymerization of NAI−DMAC with N-isopropylacrylamide and a blue fluorescent dopant. These polymers exhibit red TADF at room temperature and blue fluorescence at 70 °C, with a high ratiometric fluorescent thermal response of 32 ± 4% K −1 . Such systems are anticipated to have utility in bioimaging, drug delivery, and temperature sensing, further expanding the range of applications for red TADF materials.

Dual emission in purely organic materials for optoelectronic applications

“…10). 85 Owing to the sensitivity of the RISC process to both thermal energy and oxygen concentration, 32 was demonstrated to be a highly effective sensor for both temperature and molecular oxygen ( Fig. 9(b)).…”

Exploiting trifluoromethyl substituents for tuning orbital character of singlet and triplet states to increase the rate of thermally activated delayed fluorescence

“…10,11 The main application of TADF materials is in organic light-emitting diodes (OLEDs). [12][13][14][15] TADF materials have also been deployed in fluorescence imaging, 16,17 optical temperature sensing 18,19 and catalysis. 20 Specific molecular design features enable fast reverse intersystem crossing (rISC), which can convert up to 100% of triplet excited states to emissive singlet states, leading to TADF.…”

Naphthalimide‐Based Fluorescent Polymers for Molecular Detection

“…[ 30 ] The reported functional materials can respond to a wide array of potential analytes such as protons, [ 31 ] metal cations, [ 32–36 ] anions, [ 37–39 ] organic‐ [ 40–42 ] and biomolecules, [ 43–46 ] water vapor, [ 47 ] and temperature. [ 48 ] The most widely exploited recognition moieties for these analytes are cyclam, calixarenes, cyclodextrins and crown ethers; however, other macrocyclic and non‐macrocyclic receptors were also investigated. [ 49,50 ] Despite this progress in the creation of single‐molecule sensors, examples of fluorescent polymer sensor materials utilizing 1,8‐naphthalimides as a fluorescent reporting unit for various cations and anions are still rare.…”