Visible Light Chiral Photoinitiator for Radical Polymerization and Synthesis of Polymeric Films with Strong Chiroptical Activity
Résumé
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
PolymèresOrigine | Fichiers produits par l'(les) auteur(s) |
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