Do The Twist: Efficient Heavy‐Atom‐Free Visible Light Polymerization Facilitated by Spin‐Orbit Charge Transfer Inter‐system Crossing

Abstract

AbstractThe 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.