Imidazole-based ionic liquids for free radical photopolymerization

Ionic liquid (IL) monomers are receiving increased attention due to their versatile range of application, especially in the electrochemical and electromechanical fields. Within this study, imidazole-based ILs containing a polymerizable methacrylate (MA) group were synthesized to examine their influence on the viscosity and reactivity of typical (meth)acrylates. The IL-MAs were prepared from 1-butylimidazole and bromo methacrylates with different spacer lengths (C2–C6). The best results with respect to physicochemical properties and double bond conversions could be obtained for ILs with C3 and C6 spacers. Bulk polymerizations exhibited unusually high reactivity and double-bond conversion compared with typical mono-methacrylates. Addition of 10 wt% IL-MA to reactive diluents like hexane-1,6-diol diacrylate caused only minor reduction in reaction rate but increased final double bond conversion compared with the pure diacrylate.