NIR-Sensitized Photoinitiated Radical Polymerization and Proton Generation with Cyanines and LED Arrays

Comparison between NIR and UV-Sensitized Radical and Cationic Reactivity of Iodonium Salts Comprising Anions with Different Coordination Behavior

“…The protonated form of Rhodamine B (RhB-H) formed by protonation of RhB-L was quantified by UV/Vis measurements at 556 nm in a cuvette (d = 2 mm) [8]. This reference also provides more details regarding the correction of spectra obtained before and after exposure.…”

“…Due to the short wavelength absorption of iodoium salts (<300 nm), both radical and/or cation generation has been often pursued by a sensitized mechanism [4,5], where traditional mercury lamps [4,7], LEDs [4,[8][9][10][11] or NIR lasers [12][13][14][15] have been applied to generate initiating species. This requires to use a sensitizer exhibiting a significant absorption in the emission area of the light source.…”

“…Photochemical generation of initiating species occurs by electron transfer. This is tuned from a thermodynamic point of view by the oxidation potential of the sensitizer, the reduction potential of the iodonium cation and the excitation energy of the sensitizer [4,8,[12][13][14][15].…”

“…Alternative anions may be fluorinated phosphates with fluorinated alkyl groups ([PF 6-x (C n F 2n+1 ) x ] -; x>0, x<6) showing from our best knowledge no HF release under conditions where this phenomenon was observed in the case of PF 6 interesting alternative anion in iodonium salts. It exhibited in some cases a giant solubility in many monomers while the reactivity in NIR-photopolymers was remarkable [8,19] --anion as counter ion. Thus, such methides would form an interesting alternative compared to imides since they should exhibit according to their structure a less nucleophilicity [8,19,20].…”

“…It exhibited in some cases a giant solubility in many monomers while the reactivity in NIR-photopolymers was remarkable [8,19] --anion as counter ion. Thus, such methides would form an interesting alternative compared to imides since they should exhibit according to their structure a less nucleophilicity [8,19,20].…”