Photochromic carbazole photoinitiators for precision visible‐light photopolymerization

Abstract Two carbazole derivatives, each incorporating a naphthopyran unit and an aromatic ketone, were synthesized and evaluated as photoinitiators for radical photopolymerization. Upon visible laser irradiation, these initially colorless photo‐ and thermochromic compounds undergo a reversible ring‐opening reaction to generate colored benzophenone derivatives, which, in the presence of a co‐initiator, efficiently trigger localized radical polymerization of a tetraacrylate monomer. This approach allows the rapid and precise fabrication of thin solid objects with well‐defined geometries using visible light. © 2026 The Author(s). Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.