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Visible Light Chiral Photoinitiator for Radical Polymerization and Synthesis of Polymeric Films with Strong Chiroptical Activity

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journal contribution
posted on 2018-07-19, 14:58 authored by Assi Al Mousawi, Michael Schmitt, Frederic Dumur, Jiangkun Ouyang, Ludovic Favereau, Vincent Dorcet, Nicolas Vanthuyne, Patxi Garra, Joumana Toufaily, Tayssir Hamieh, Bernadette Graff, Jean Pierre Fouassier, Didier Gigmes, Jeanne Crassous, Jacques Lalevée
3-Methyl-4-aza­[6]­helicene (A6H) enantiomers were synthesized and proposed as high-performance visible light photoinitiators and/or photosensitizers for the free radical polymerization (FRP) of (meth)­acrylates upon visible light exposure using inexpensive and safe light-emitting diodes (LEDs) at 405 nm. Excellent polymerization initiating abilities were found, and high final conversions were obtained. Remarkably, an exceptional strongly enhanced chiral property of the polymer films was observed in the presence of the enantiopure azahelicenes. This is the first example of chiral properties introduced in polymer films by the photoinitiator through photopolymerization processes. It is of high interest as these latter are very fast and inexpensive polymerization techniques. Remarkably, contrary to chiral properties introduced by using a combination of commercial photoinitiator and chiral dopant, a dual behavior is found here for A6H. A full picture of the involved chemical mechanisms is given.

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