Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy
FTIR spectra of plasticized grafted natural rubber–LiCF3SO3 electrolytes
Introduction
The discovery of ionic conductivity in polymer based on hosts complexed with salts [1], [2], [3], [4] has generated research activities that lead to significant advances in lithium batteries. Studies [5], [6] have sought to investigate on the factors governing ionic conduction, such as ion pairing and ion aggregation. The introduction of plasticizers with low molecular weight such as propylene carbonate (PC), ethylene carbonate (EC), dibuthyl phthalate (DBP) and diocthyl adipate (DOA) plays an important role in conducting material with sufficient mobility of ionic conduction. In most cases the role of plasticizer is as a conductivity enhancer, but its mode of operation is complex [7].
Polymers such as poly-vinyl chloride (PVC), poly-methylmethacrylate (PMMA), poly-ethylene oxide (PEO) and poly-vinylidene fluoride (PVdF) have been used as matrices for plasticized polymer electrolytes. Blending of different polymers is the most promising and feasible approach [8], [9] and has become technically important material. Although a large number of combinations of polymers are possible, there are a few that lead to a totally miscible systems [10], [11], [12], [13], [14], [15].
Razali Idris et al. [16], [17] explored 25% epoxidised NR, 50% epoxidised NR and PMMA grafted NR as a potential candidate for polymer electrolytes in lithium batteries. NRs various chemical modifications have been attempted to modify its properties and extend its use [18], [19], [20], [21]. One such modification is the graft polymerization with methyl methacrylate monomer. The polar PMMA provided the path for ion conduction and the nonpolar NR gave the desired properties in its lightweight [14] and elasticity. MG30 gives good retention at elevated temperatures and good electrical properties [22]. Owing to their interesting properties, MG30 is employed in this work.
FTIR spectroscopy studies were done to establish the interactions between the polymer and salt which identify any changes in the electronic levels of the atoms and to investigate the influence of the plasticizer (EC), on the salted polymer electrolyte. The studies of polymers FTIR consist of analyzing and identifying polymeric compositions and subtle structural variations such as tacticity and neighboring group interactions.
Section snippets
Experimental
MG30 was obtained commercially and LiCF3SO3 was obtained from Aldrich. Prior to the preparation of polymer electrolytes, LiCF3SO3 were dried at 100 °C for 2 h in order to eliminate any trace amount of water. All the electrolyte samples were prepared by solvent cast method. MG30 was cast on glass to obtain a dry rubber film. The dried rubber film was sliced into grain size to ease the dissolution process. The required amounts of grafted polymer were prepared by dissolving it in stoppered flask
Results and discussion
FTIR spectroscopy is a powerful tool to monitor the vibrational energy levels in the region of different molecules. The IR spectra of PMMA, MG30 and polyisoprene are shown in Fig. 1. In this study, interests have been shown on oxygen atoms, which acted as electron donor atoms in the structure of the polymer host. When salt is added to the polymer, the oxygen atoms with lone pair of electron form a dative bond with Li+ ion from the salt and hence a polymer–salt complex would be formed. In the
Conclusions
The complex formations in MG30–LiCF3SO3 and LiCF3SO3–EC systems had been confirmed from the FTIR studies. There is no interaction between MG30 and EC at the CO bending and stretching modes and the ring breathing region. It was also concluded that the plasticizer molecules had penetrated the salted polymer matrix in MG30–LiCF3SO3–EC complex.
Acknowledgements
The authors would like to thank the government of Malaysia for the PJP grant and vote F0185/2004A and F0710/2004D that enable this work to be carried out.
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2017, Energy Conversion and ManagementCitation Excerpt :Functional groups corresponding to the major absorption peaks of the FTIR spectra are listed in Table 8. It should be noted that the absorption peaks 2924 and 2852 cm−1 are typical of EPDM rubber arising from the saturated hydrocarbon chain backbone of aliphatic alkyl symmetric/asymmetric CH2 stretching vibration [59–61]. The absorption bands 1461 and 1380 cm−1 are assigned to CH2 scissoring vibration and CH bending vibration of CH3 from the propylene and ethylene unit, respectively [60,61].