Coumarinacyl Bromides as Unimolecular Photoinitiators for Conjugated Polymer Synthesis under Visible and NIR Light Irradiation

Abstract

Two coumarinacyl bromides, 3‐(bromoacetyl)coumarin (BAC) and 3‐(bromoacetyl)‐7‐methoxycoumarin (BACO), were developed for the photopolymerization of N‐ethylcarbazole to construct conjugated polymer under visible and near‐infrared light irradiation. BAC outperformed the conventional phenacyl bromide photoinitiator, exhibiting superior photoinitiation performance due to its optimal absorption characteristics and electron transfer efficiency. The obtained poly(N‐ethylcarbazole) was thoroughly characterized, demonstrating the successful synthesis of a conjugated polymer with desired properties. Dedoping led to improved optical properties and film morphology. The polymerization mechanism was elucidated using transient absorption spectroscopy, revealing efficient electron transfer from the excited photoinitiators to N‐ethylcarbazole.