Current Topics in Electrochemistry, (2010) 15: 17-24 1 Solid Polymeric Electrolyte of Poly(Methyl Methacrylate)– 49% Poly(Methyl Methacrylate) Grafted Natural Rubber– Propylene Carbonate–Lithium Tetrafluoroborate A. Ahmad 1,2 , M.Y.A. Rahman 3* , S.P. Low 1 , M.S. Su’ait 1,2 1 School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600, Bangi, Selangor, Malaysia 2 Polymer Research Center, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600, Bangi, Selangor, Malaysia 3 College of Engineering, Universiti Tenaga Nasional, 43009, Kajang, Selangor, Malaysia *Corresponding author: yusri@uniten.edu.my Abstract Effect of propylene carbonate (PC) on a solid polymer electrolyte containing poly(methyl methacrylate) PMMA, 49% of poly(methyl methacrylate)-grafted natural rubber (MG49) and lithium tetrafluoroborate (LiBF 4 ) salt has been studied. Solid polymer electrolyte of PMMA-MG49-PC-LiBF 4 prepared by solution casting technique produced a freestanding film. FTIR analysis confirmed that an interaction occurs between lithium salt and oxygen atoms at carbonyl and ether groups in polymer host with the presence of plasticizer, PC. Morphology studies by SEM show that the addition of PC reduces the particles size of LiBF 4 salts and increases the dark surface of the electrolytes systems. As a consequence, the surface of the electrolytes becomes smoother. This indicates that the addition of PC into PMMA-MG49-LiBF 4 have made the electrolyte system became more amorphous. The addition of PC enhanced the ionic conductivity of the electrolytes. It was observed that the conductivity of the electrolyte increases with PC concentration. The highest conductivity was obtained at 50 wt. % PC with conductivity value at 7.4×10 -6 Scm -1 as compared to the ionic conductivity PMMA-MG49-LiBF 4 without plasticizer was found to be 2.7×10 -8 Scm -1 . Keywords plasticizer, propylene carbonate (PC), poly(methyl methacrylate) (PMMA), 49 % of poly(methyl methacrylate)-grafted natural rubber (MG49), Lithium tetrafluoroborate Introduction A polymer electrolyte consists of an inorganic salt that is dissolved in a polymer host. Conductive polymer-salt complexes were first described in the early 1970’s and were quickly adopted by the electrochemical community, recognizing its potential for being a flexible, plastic, ion transporting medium for vital applications such as energy storage and electrochemical displays [1]. Therefore, modification of polymer electrolyte has been developed drastically to widen its usage [2]. Due to the increasing demand of polymer electrolyte in the market, several types of polymer such as poly(ethylene oxide) (PEO), poly(methyl methacrylate) (PMMA), poly(vinyl chloride) (PVC) and poly(vinylidene fluoride) (PVdF) have been used as polymer host for polymer electrolyte systems [3-7]. The introduction of plasticizers with low molecular weight such as propylene carbonate (PC) and ethylene carbonate (EC) plays an important role in conducting material with sufficient mobility of ionic conduction [8]. This is because these plasticizers reduce the glass transition temperature, T g of the polymer, which helps to increase the segmental motion of the polymer backbone and generate free volume [3,8]. Therefore, the ions can migrate easily through the free space, resulting in ionic conductivity enhancement.