Visible light-induced photopolymerization of Deep Eutectic Monomers, based on methacrylic acid and tetrabutylammonium salts with different anion structures
Samuel Wierzbicki, Kacper Mielczarek, Monika Topa-Skwarczyńska, Krystian Mokrzyński, Joanna Ortyl, Szczepan Bednarz
Abstract
Deep Eutectic Monomers were prepared by dissolution of selected tetrabutylammonium salts serving as hydrogen bond acceptors (HBA) in methacrylic acid (MAA) acting both as hydrogen bond donor (HBD) and vinyl monomer. In this study, we systematically investigate the influence of chloride, nitrate, hydrogensulphate and fluoroborate anions on properties of DEMs and the course of radical photopolymerization. By Combining FTIR, 1H and 13C NMR spectroscopy we found the that degree of coordination of MAA in DEMs by anions follows the order: Cl− > NO3– > HSO4− ≫ BF4−. Moreover, the studies indicated that the strength of hydrogen bonds between HBD and HBA in DEMs is lower than in MAA dimers. Real-time FT-IR spectroscopy studies of photopolymerization of DEMs indicate that the mixtures formed from MAA and tetrabutylammonium fluoroborate show significant lower initial photopolymerization rate in comparison with other investigated DEMs, which polymerize with similar rates.