Naphthoquinone-based imidazolyl esters as blue-light-sensitive Type I photoinitiators

In this work, a series of Type I photoinitiators (PIs), based on the naphthoquinone scaffold, were designed and synthesized for the first time in order to induce photopolymerization under visible light. As a result, these PIs exhibit excellent photoinitiation abilities in the presence of acrylate monomers upon LED@405 or @455 nm irradiation. Interestingly, some compounds have better photoinitiation performance than the benchmark Type I phosphine-oxide, i.e. diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) upon exposure to LED@455 nm. Chemical mechanisms supporting the photopolymerization process were investigated through different techniques as well as theoretical calculations. In addition, the newly proposed structures were also investigated in two-component photoinitiating systems and exhibited a higher efficiency in free radical photopolymerization. Finally, a direct laser writing approach was successfully used to fabricate 3D objects.

Automated summary

A series of Type I photoinitiators based on the naphthoquinone scaffold were designed and synthesized for the first time to induce photopolymerization under visible light. These photoinitiators exhibited excellent photoinitiation abilities and some even outperformed the benchmark Type I phosphine-oxide. The chemical mechanisms supporting the photopolymerization process were investigated, and the newly proposed structures showed higher efficiency in free radical photopolymerization. Additionally, 3D objects were successfully fabricated using a direct laser writing approach.