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

• Published in: ACS applied materials & interfaces 2020-04, Vol.12 (17), p.20000-20011
• Main Authors: Christopherson, Cheyenne J, Mayder, Don M, Poisson, Jade, Paisley, Nathan R, Tonge, Christopher M, Hudson, Zachary M
• Format: Article
• Language: English
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.0c05257

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 (λmax = 340 nm in toluene) and red-delayed fluorescence from the charge-transfer process (λmax = 633–711 nm in toluene). This dual emissive property was utilized to create red-to-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.