Photoinitiation under soft irradiation conditions novel three-component systems

Photoinitiation under soft irradiation conditions novel three-component systems 

In the past 3-4 years, huge efforts have been deployed to develop PISs able to initiate the polymerization of low-viscosity matrices (radical or cationic) under soft irradiation conditions, i.e. visible lights, low intensity (2-30 mW/cm ) and under air [LAL 14a]. They require the design of particularly reactive systems and involve novel strategies for an efficient production of radical or cationic initiating species. Such systems can successfully operate in high-viscosity media or/and under intense light sources. 

As stated above, the low incident light intensity of a given source must be counterbalanced by an initiation quantum yield Oj as high as possible and enhanced absorption properties of the dye in order to achieve high Rp and Cf The most performant new PISs are the recently developed Dye/silane (or NVK)/iodonium salt three-component systems where two significant 

Other efficient three-component systems are based on the Dye/amine AH/alkyl halide R -X combinations. Examples of Dye are hydrocarbons, indanones, thiobarbituric acid, ruthenium or iridium complexes, etc. (see also below). They work according to the sequence [1.40], R and A being the initiating radicals. 

Dyes with red-shifted absorptions and high molar extinction coefficients 

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