No abstract

Carboxylic acids of various carbon chain lengths (Cn); i.e. butanoic acid (C4), octanoic acid (C8), dodecanoic acid (C12) and hexadecanoic acid (C16) have been used to organically modify silicon dioxide (SiO2). The acid modification involve replacing the hydrogen atom of the silanol group (Si-OH) of SiO2 with the RnCOO-of the acid via esterification technique. SiO2 and acid modified SiO2 (MoCn-SiO2) were used as filler in preparation of polymethyl methacrylate/50% epoxidized natural rubber electrolytes containing SiO2 (PEL-SiO2) and MoCn-SiO2 (PEL-MoCn-SiO2) via solvent casting method with lithium tetrafluoroborate (LiBF4) as dopant salt. Field-emission scanning electron microscopy (FESEM) analysis of PEL-SiO2 and PEL-MoCn-SiO2 films show LiBF4 accumulated to the fillers. Fourier-transform infrared spectroscopy (FTIR) analysis confirmed formation of hydrogen bonding between LiBF4 with fillers and polymers in the polymer electrolyte films. Interestingly, the ionic conductivity of PEL-MoCn-SiO2 films increases as the Cn of acids increased with the highest ionic conductivity of 5.56 x 10-7 Scm-1 was achieved in PEL-MoC12-SiO2 film.

Previously, it was found that the brittle properties of polymehyl methacrylate (PMMA) film has been improved when blended with epoxidised natural rubber 50 % (ENR 50) hence enhanced the ionic conductivity of PMMA electrolytes. However, the PMMA and ENR 50 blend was not homogeneous thus limits the overall performance of the blend. Therefore, in this study, silicon dioxide (SiO2) filler was incorporated into the polymer blend film to improve the homogeneity and the ionic conductivity of the system. It was found that the addition of SiO2 has succesfully improve the homogeneity of the blend by assisting the dispersion of ENR 50 in the blend and hence provide better conducting path for the lithium ion. This was confirmed from its differential scanning calorimetry (DSC), fourier transform infrared (FT-IR) and optical microscopic (OM) analyses.