A New Highly Efficient Amine-Free and Peroxide-Free Redox System for Free Radical Polymerization under Air with Possible Light Activation

• Published in: Macromolecules 2016-09, Vol.49 (17), p.6296-6309
• Main Authors: Garra, P, Dumur, F, Morlet-Savary, F, Dietlin, C, Fouassier, J. P, Lalevée, J
• Format: Article
• Language: English
• Subjects: Chemical Sciences; Material chemistry
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/acs.macromol.6b01615

Efficient redox initiating systems for radical polymerizations under air usually show some severe drawbacks such as handling and toxicity of the oxidizing agent (peroxides, persulfates, peroxidiphosphates, disulfides, etc.), toxicity of the reducing agent (aromatic amines such as 4-N,N-trimethylaniline), and more generally a low top surface conversion due to high oxygen inhibition. The originality of the proposed paper relies on the development of new redox initiating systems for the polymerization of (meth)­acrylate monomers that does not contain any hazardous compound (no peroxide) and is amine-free (low toxicology issues). And these new systems that possess the advantages of redox-initiated polymerization (possibility to cure thick samples) can also be photoactivated in order to have a faster and better curing of the surface of the sample (advantages of the photopolymerization to overcome the oxygen inhibition). The light activations presented in this work have been done with light-emitting diodes (LEDs) as they have a low energy consumption and are safer to the user than UV light. Two wavelengths have been used: 405 nm (in the blue range of the spectrum) and 780 nm (in the near-infrared) showing the versatility of these new photo/redox initiating systems. In particular, the reactivity in the near-IR (not related to any heating of the sample) is a very original result. In addition with the presentation of the performance of the new systems in polymerization and photoactivated polymerization, a full analysis of the chemical mechanisms and species involved has been performed. Remarkably, the new proposed Cu­(acac)2/2dppba system is also able to overcome the oxygen inhibition for free radical redox (photo)­polymerization.