Papers by Author: Norazlin Zainal

Abstract: In this work, electrolyte films based on epoxidized natural rubber-50 (ENR-50) and lithium imide (LiN(SO₂CF₃)₂) salt were prepared using solution casting method. X-ray diffraction pattern for undoped ENR-50 shows a broad peak which indicated amorphous nature of the film. The intensity of ENR-50 peak decreases with increase in salt concentration. Thermal property study was carried out using Differential Scanning Calorimetry (DSC) to determine glass transition temperature, Tg. The DSC result displays an increasing trend of Tg with increase in salt concentration and opposite to the trend of variation of conductivity with salt concentration. This indicates that the increase in Tg dose not give adverse effect on ionic conductivity. The increase in Tg with concentration of salt may be due to formation of transient cross-linking between ENR-50 chains via the coordinated interaction between ENR-50 chains and LiN(SO₂CF₃)₂. The highest room temperature ionic conductivity obtained is in the order of 10^-5 S cm^-1 for the film containing 50 wt.% of LiN(SO₂CF₃)₂. The ionic conductivity of this electrolyte system increases with increase in temperature and obeys the Vogel-Tammam-Fulcher (VTF) relation in the temperature range of 303–373 K. The increase in ionic conductivity of the electrolyte system could be correlated to increase in number of charge carriers and the migration rate of charge carriers.

Abstract: Free standing polymer electrolyte films comprising of ammonium trifluoromethane sulfonate in poly(ethyl methacrylate) were prepared and characterized. The structural and electrical properties of the polymer electrolytes were investigated by X-ray diffraction and a.c. impedance spectroscopy, respectively. The formation of polymer-salt complex has been confirmed by Fourier transform infrared spectroscopy study. Conductivity of the polymer electrolytes increased with salt content. The highest ionic conductivity in the order of 10-5 S cm-1 at room temperature was achieved for the system with 35 wt% of ammonium salt. The temperature dependence of conductivity obeyed the Vogel-Tammam-Fulcher relation. The activation energy has been calculated from the VTF formalism. The ionic transference number of the mobile ions estimated by Wagner’s polarization method was close to unity for the highest conducting sample implying that the conductivity was contributed by ions which was expected to be protons.

Abstract: Ionic liquid based on imidazolium cation; 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMITFSI) has been incorporated with epoxidized natural rubber-50 (ENR-50) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to obtain electrolyte material. Fourier transform infrared spectroscopy (FTIR) spectra showed evidence of complexation between ENR-50, EMITFSI and LiTFSI. Glass transition temperature, T_g displayed an increasing trend with increase in salt concentration. The incorporation of EMITFSI resulted in an increase in ionic conductivity. The increase in ionic conductivity was attributed to the role of ionic liquid which reduced T_g, thus, facilitated ion conduction in the system. The highest ionic conductivity at room temperature was 5.72 ´ 10^-4 S cm^-1 for sample containing 20 wt% of EMITFSI and 50 wt% of LiTFSI.