Enhancement of ionic conductivity and structural properties by 1-butyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid in poly(vinylidene fluoride-hexafluoropropylene)-based polymer electrolytes

Polymer electrolytes (PEs) with poly(vinylidene fluoridehexafluoropropylene) [P(VdFHFP)] as the polymer host and doped with lithium trifluoromethanesulfonate (LiTf) and 1-butyl-3-methylimidazolium trifluoromethanesulfonate (BMIMTf) were synthesized via a solution casting method. This P(VdFHFP)/LiTf/BMIMTf-based PE achieved about 1.8 x10-3 S/cm at room temperature with 100 parts by weight (pbw) of BMIMTf. A discrepancy was observed when 25 pbw of BMIMTf was doped into the system and was related to the reactivity of Li+ and 1-butyl-3-methylimidazolium cation (BMIM+), which could be corroborated with differential scanning calorimetry scans. Fourier transform infrared spectroscopy and X-ray diffraction revealed the role of P(VdFHFP) as merely a mechanical support with no direct interaction with BMIMTf. Photoluminescence was also used to detect structural alterations in the local environment of PE. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2012