Recent advances on visible light Thiophene-based photoinitiators of polymerization

Abstract

Visible light photopolymerization has given a revival of interest to photopolymerization due to its recent use in 3D printing. With aim at developing visible light photoinitiating systems, structures disconnected from the traditional photoinitiators are more and more widely examined. Besides, several parameters such as the excited state lifetimes, the redox properties or the molar extinction coefficients of the newly prepared photoinitiators have to be considered in order photoinitiators to efficiently interact with the different additives introduced into the photocurable resins. In this field, thiophene is extensively used in Organic Electronics due to its low oxidation potential, its facile chemical modification and the possibility to design chromophores absorbing all over the visible range. Considering the numerous thiophene derivatives that have been prepared all over the years, thiophene was thus a candidate of choice for the design of visible light photoinitiators of polymerization. Over the years, structures of thiophene-based photoinitiators have greatly evolved and Type I or Type II photoinitiators have notably been developed. In this review, an overview of the recent advances concerning thiophene-based photoinitiators is provided. To evidence the interest of these structures, comparisons with reference photoinitiating systems are provided.