Lamp vs. Laser: A Visible Light Photoinitiator that Promotes Radical Polymerization at Low Intensities and Cationic Polymerization at High Intensities

Abstract

A visible light absorbing, anthraquinone derivative 1-tosyloxy-2-methoxy-9,10-anthraquinone (QT) mediates both cationic and radical polymerizations depending on the intensity of visible light used. A previous study showed that this initiator generates para-toluenesulfonic acid through a stepwise, two-photon excitation mechanism. Thus, under high intensity irradiation, QT generates acid in sufficient quantities to catalyze the cationic ring opening polymerization of lactones. However, under low intensity (lamp) conditions, the two-photon process is negligible, and QT photooxidizes DMSO, generating methyl radicals which initiate the RAFT polymerization of acrylates. This dual capability was utilized to switch between radical and cationic polymerizations to synthesize a copolymer using a one-pot procedure.

Lamp vs Laser: A Visible Light Photoinitiator That Promotes Radical Polymerization at Low Intensities and Cationic Polymerization at High Intensities

“…A preliminary version of this work was deposited on ChemRxiv on Jan 17, 2023. 47 ■ RESULTS AND DISCUSSION Cationic ROP. The ROP of lactones is a prominent technique for preparing polyesters; however, only in recent years, it has been mediated by light.…”

“…Having a photosensitizer that is capable of mediating more than one type of polymerization allows for the preparation of more complex materials while maintaining simplicity of the reaction mixture. A preliminary version of this work was deposited on ChemRxiv on Jan 17, 2023 …”