Do The Twist: Efficient Heavy-Atom-Free Visible Light Polymerization Facilitated by Spin-Orbit Charge Transfer Inter-system Crossing |
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Authors: | Dr Ain Uddin Seth R Allen Adrian K Rylski Connor J O'Dea Dr Jack T Ly Dr Tod A Grusenmeyer Dr Sean T Roberts Dr Zachariah A Page |
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Institution: | 1. Department of Chemistry, The University of Texas at Austin, 78712 Austin, TX, USA;2. Materials and Manufacturing Directorate, Air Force Research Laboratory, 45433 Wright-Patterson AFB, OH, USA |
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Abstract: | The use of visible light to drive polymerizations with spatiotemporal control offers a mild alternative to contemporary UV-light-based production of soft materials. In this spectral region, photoredox catalysis represents the most efficient polymerization method, yet it relies on the use of heavy-atoms, such as precious metals or toxic halogens. Herein, spin-orbit charge transfer intersystem crossing from boron dipyrromethene (BODIPY) dyads bearing twisted aromatic groups is shown to enable efficient visible light polymerizations in the absence of heavy-atoms. A ≈5–15× increase in polymerization rate and improved photostability was achieved for twisted BODIPYs relative to controls. Furthermore, monomer polarity had a distinct effect on polymerization rate, which was attributed to charge transfer stabilization based on ultrafast transient absorption and phosphorescence spectroscopies. Finally, rapid and high-resolution 3D printing with a green LED was demonstrated using the present photosystem. |
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Keywords: | 3D Printing BODIPY Photocatalysis Triplet State Photoredox Visible Photochemistry |
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