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Aqueous RAFT Photopolymerization with Oxygen Tolerance

Shanmugam, Sivaprakash, Xu, Jiangtao, Boyer, Cyrille
Macromolecules 2016 v.49 no.24 pp. 9345-9357
air, ascorbic acid, molecular weight, oxygen, photocatalysts, polymerization, polymers, porphyrins, singlet oxygen, solvents, water solubility, zinc
The emergence of light regulated controlled/living radical polymerization adds a new layer of control over polymerization. Light mediated polymerizations afford simple and facile route to modulate polymerization rate through manipulation of light intensity and by switching on/off the light source. Such mediation has resulted in the synthesis of 3D surfaces with both spatial and temporal control. However, these techniques present a major limitation in terms of oxygen tolerance and require the use of organic solvent. In this contribution, we report an efficient aqueous polymerization system capable of being activated under visible light in the presence of oxygen. We perform aqueous photopolymerization in the presence of water-soluble zinc porphyrin photocatalyst (Zn(II) meso-tetra(4-sulfonatophenyl)porphyrin, ZnTPPS⁴–) with ascorbic acid as singlet oxygen quencher in both open and closed vessels. Polymers could be prepared without prior deoxygenation with good control over the molecular weight and polydispersity. In addition, polymerization in the presence of air could be achieved with a short inhibition period.