Recent advances on phenothiazine-based oxime esters as visible light photoinitiators of polymerization

Visible light photopolymerization is facing numerous challenges with regards to the necessity to develop energy-efficient photoinitiating systems that can be activated under low light intensity. Combined with the recent requirement to drastically simplify the composition of the photocurable resins, the development of monocomponent photoinitiating systems has been the focus of intense research efforts. In this field, Type I photoinitiators and more precisely oxime esters that can generate radicals by homolytic cleavage of a NO bond constitute candidates of choice. Among oxime esters, phenothiazine has been rapidly identified as an excellent chromophore due to its inherent absorption in the visible range, facilitating the design of visible light oxime esters. In this review, on overview of the different phenothiazine-based oxime esters reported to date is provided