Preparation and polymerization analysis of poly-(alkenyl-based di-ionic ionic liquid)

•Alkenyl groups were introduced into the linker groups of di-ionic ionic liquids.•PVDILs were prepared via a one-pot free radical polymerization in aqueous solution.•Alkenyl groups had a significant influence on the molecular weight of the PVDILs.•The PVDILs have alkenyl functional groups. In this study, bis-imidazole-containing ionic liquids (VDILs) featuring halide counteranions and substituted with different numbers of alkenyl groups were designed and synthesized. The VDILs were further subjected to a one-pot free radical polymerization in aqueous solution, forming hydrophobic PVDILs. GPC, FT-IR, XPS, and XRD were performed to determine the influence of the number and position of the alkenyl groups in the VDIL monomers on the molecular weight, molecular weight distribution, and polymeric structure of the PVDILs. The GPC results showed that the position of the alkenyl groups had a significant influence on the molecular weight of the PVDILs. The linker alkenyl group in the VDIL monomer was easier to polymerize than the alkenyl group connected to the N(1) atom of the imidazole ring of the VDIL due to the steric bulk of the counteranions, which mitigated cross-polymerization of the vinyl groups. As the interconnected polymeric network was being formed, the steric bulk of the anions hindered chain growth, resulting in a lower-than-expected molecular weight of PVDIL-3. XPS and FT-IR results indicated that there were still a certain number of alkenyl groups that remained in the PVDIL-1 and PVDIL-3 structures after polymerization, with the PVDIL-3 sample containing 3% more alkenyl groups than PVDIL-2. This study demonstrates a new method for the polymerization of alkenyl-based DILs and provides a foundation for the application of PDILs.