Kinetic Studies of Photopolymerization of Monomer-Containing Deep Eutectic Solvents

The kinetics of photopolymerization in deep eutectic solvents (DESs) is investigated through real-time Fourier transform-infrared spectrometry (RT-FTIR). The systems of this study are choline chloride (ChCl) DESs made of acrylic acid and methacrylic acid (DES monomers) and a nonreactive analog isobutyric acid (IBA). The DES consisting of the analog also contains the monomer methyl methacrylate (MMA). Analysis of the evolution of conversion indicates dramatic increase in polymerization rate when comparing the polymerization of the DES monomers to pure monomer polymerization. A significant increase in polymerization rate is also seen in the systems that include a methyl ester derivative of the hydrogen bond donor monomer (e.g., MMA) in a nonpolymerizable DES (e.g., IBA-ChCl). It is proposed that the increased solvent viscosity, preorganization due to hydrogen bonding, and the polarity of the DES around the monomers play a role in the enhancement of the polymerization rate.