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

A. Al Mousawi (1, 2) , M. Schmitt (1) , F. Dumur (3) , J. Ouyang (4) , L. Favereau (4) , V. Dorcet (4) , N. Vanthuyne (5) , P. Garra (1) , J. Toufaily (2) , T. Hamieh (2) , B. Graff (1) , J.P. Fouassier (1) , D. Gigmes (3) , Jeanne Crassous (4) , J. Lalevee (1)

1 IS2M - Institut de Science des Matériaux de Mulhouse
2 LU / ULB - الجامعة اللبنانية [بيروت] = Lebanese University [Beirut] = Université libanaise [Beyrouth]
3 ICR - Institut de Chimie Radicalaire
4 ISCR - Institut des Sciences Chimiques de Rennes
5 ISM2 - Institut des Sciences Moléculaires de Marseille

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. © 2018 American Chemical Society.

Mots clés: Photoinitiators; Photosensitizers; Photopolymerization; Light; Light emitting diode (LEDs); Photo-initiator; Polymer films; Semiconducting films; Stereochemistry; Chemical mechanism; Chiral dopant; Chiral properties; Enantiopure; Free radicals; Atom transfer radical polymerization; Visible light; Free radical polymerization

Domaines: Polymères

A. Al Mousawi, M. Schmitt, F. Dumur, J. Ouyang, L. Favereau, et al.. Visible Light Chiral Photoinitiator for Radical Polymerization and Synthesis of Polymeric Films with Strong Chiroptical Activity. Macromolecules, 2018, 51 (15), pp.5628-5637. ⟨10.1021/acs.macromol.8b01085⟩. ⟨hal-01874726⟩