In this study, 1-n-tetradecyl-3-methylimidazolium bromide ([C(14)mim]Br), one kind of imidazolium ionic liquids (imi-IL), was incorporated into polypropylene (PP) via melting blend. The structure and properties of PP/[C(14)mim]Br blend were investigated by differential scanning calorimetry (DSC), dynamical mechanical analysis (DMA), and thermogravimetric analysis (TGA). DSC results show that the [C(14)mim]Br has effects on the melting and crystallization process so that PP and PP/[C(14)mim]Br blends (weight ratio is 100/3) have different melting and crystallization temperature. Results of DMA show that the [C(14)mim]Br has the effects on the plasticization and crystallization of PP, and the glass transition temperature (T.) of PP decreases around 11 degrees C when 3 weight shares of [C(14)mim]Br were incorporated into 100 weight shares of PP. Moreover, both tensile strength and impact strength of PP have been improved reasonably in this situation. TGA also shows the thermal stability of PP is not affected by the [C(14)mim]Br, which was incorporated into it though its molecule is small. (c) 2008 Wiley Periodicals, Inc.