The structural and electrical properties of flexible PMMAil/LiTf films

Abstract

To date, poly (methyl methacrylate) (PMMA) in film form, exhibited the most mechanical stability towards lithium electrode. Unfortunately, commercial PMMAs even at high molecular weight were not able to produce flexible film. This is due to the presence of oxygen atoms that incline to form interchain crosslinking via hydrogen bonding. Therefore, the opportunity of the PMMA chains to form hydrogen bonding was hindered by encapsulating 1-methyl-3-pentamethyldisiloxymethylimidazolium bis(trifluoromethylsulfonyl)imide, [(SiOSi)C1C1im][NTf2] during free radical polymerization of MMA. It was found that, this newly synthesized PMMA containing IL (PMMAIL) produced flexible and transparent films with ionic conductivity of ~10-7 S cm-1. Though the ionic conductivity obtained is comparable with other doped PMMA film electrolytes that had been studied, it is still considered as low for application in energy storage devices. Thus, in this study, the conductivity of the PMMAIL was further enhanced by the addition of lithium triflate (LiTf) using solvent casting technique. The highest ionic conductivity for this doped PMMAIL achieved ~10-4 S cm-1 which fits the minimum requirement for energy storage devices. As confirmed from Fourier Transform Infrared spectroscopy (FTIR) and Optical Microscope (OM) analyses, the increase in ionic conductivity was due to the suppression of the semicrystalline structure of PMMAIL owing to the added salt.