Robust,Ultrafast and Reversible Photoswitching in Bulk Polymers Enabled by Octupolar Molecule Design |
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| Authors: | Long Fang Ziwei Lin Yang Zhang Bin Ye Jing Li Qishan Ran Xiaotong Wang Meijia Yang Prof Zhongke Yuan Prof Xiaofeng Lin Prof Dingshan Yu Prof Xudong Chen Prof Quan Li |
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| Institution: | 1. Key Laboratory for Polymeric Composite and Functional Materials of Ministry of Education, Key Laboratory of High Performance Polymer-based Composites of Guangdong Province, GBRCE for Functional Molecular Engineering, School of Chemistry, Sun Yat-sen University, Guangzhou, 510006 China;2. School of Computer Science and Engineering, Sun Yat-sen University, Guangzhou, 510275 China;3. Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macao SAR, 999078 China;4. School of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou, 510006 China
Guangdong Laboratory of Chemistry and Fine Chemical Industry Jieyang Center, Jieyang, 515200 China;5. School of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou, 510006 China;6. Institute of Advanced Materials and School of Chemistry and Chemical Engineering, Southeast University, Nanjing, 211189 China |
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| Abstract: | Improving the photoswitching rate and robustness of photochromic molecules in bulk solids is paramount for practical applications but remains an on-going challenge. Here, we introduce an octupolar design paradigm to develop a new family of visible light organic photoswitches, namely multi-branched octupolar Stenhouse Adducts (MOPSAs) featuring a C3-symmetrical A3-(D-core) architecture with a dipolar donor–acceptor (D–A) photochrome in each branch. Our design couples multi-dimensional geometric and electronic effects of MOPSAs to enable robust ultrafast reversible photoswitching in bulk polymers. Specifically, the optimal MOPSA (4 wt %) in commercial polyurethane films accomplishes nearly 100 % discoloration in 6 s under visible light with ∼ 100 % thermal-recovery in 17.4 s at 60 °C, while the acquired kinetics constants are 3∼7 times that of dipolar DASA counterpart and 1∼2 orders of magnitude higher than those of reported DASAs in polymers. Importantly, the MOPSA-doped polymer films sustain 500 discoloration/recovery cycles with slow degradation, superior to the existing DASAs in polymers (≤30 cycles). We discover that multi-dipolar coupling in MOPSA enables enhanced polarization and electron delocalization, promoting the rate-determining thermal cyclization, while the branched and non-planar geometry of MOPSA induces large free volume to facilitate the isomerization. This design can be extended to develop spiropyran or azobenzene-based ultrafast photochromic films. The superior photoswitching performance of MOPSAs together with their high-yield and scalable synthesis and facile film processing inspires us to explore their versatile uses as smart inks or labels for time-temperature indicators, optical logic encryption and multi-levelled data encryption. |
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| Keywords: | Photochromic films octupole donor–acceptor Stenhouse Adducts time-temperature indicators information encryption |
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