Two types of ionicliquids (ILs), 1-(3-hexenyl)-3-methyl imidazoliumiodide and 1-(3-butenyl)-3-methyl imidazoliumiodide, are synthesized by introducing an unsaturated bond into the side alkyl chain of the imidazolium cation. These new ionicliquids exhibit high thermal stability and low viscosity (104 cP and 80 cP, respectively). The molecular dynamics simulation shows that the double bond introduced