Among the controlled radical polimerization methods, Atom Transfer Radical Polymerization (ATRP) has been the most-widely used method as it has demonstrated high tolerance towards many functional groups available in the initiator and monomer structure. The major drawback associated with the ATRP process is the requirement of the low oxidation state copper halide catalysts, which are hard to remove from the polymers obtained. The residual inorganic materials in these polymers prevent the application of these materials especially in medical or bioapplications. In addition, these are thermal processes and application of photochemical strategies were sometimes connected with problems. Thus, additional innovative research is required due to the insufficiency of adaptation of light into the present technologies. It is therefore important to realize the syntheses of telechelic polymers, block, graft and star copolymers by light induced approaches as they provide low-energy requirements and simpler experimentation procedures. Recently, it has been demonstrated that some controlled polymerization techniques can be performed in the absence of inorganic catalysts by the use of light being the smallest reagent[1]. We employed NIR-acting photoinitiating system as new metal-free photo-ATRP systems comprising cyanines as sensitizers with the same number of methine groups. For this purpose, we used NIR-LEDs emitting at 790 nm and halogen lamp to initiate photo-ATRP. These sensitizer exhibit either a positive charge (1a), negative charge (1c) or neutral substitution pattern (1b). 1b and 1c resulted in initiation of radical polymerization of methacrylates in combination with an alkyl halide and an amine. However, 1a did not show any action in the polymerization process applying NIR-LED exposure. This may be explained by an oxidation mechanism based on singlet excited states because the electron-rich canines 1b and 1c would follow this route. Our contribution can be seen as a new approach to initiate radical photopolymerization. Furthermore, exposure experiments resulted in polymers which were characterized with GPC.

Visible and NIR light photoinduced metal-free atom transfer radical polymerization

255th National Meeting (2018)

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