FTIR spectra of plasticized grafted natural rubber–LiCF3SO3 electrolytes

Chemical modification of natural rubber (NR) has frequently been attempted to improve the performance in specific application. 30% poly(methyl metacrylate) (PMMA) grafted into NR (MG30) has been explored as a potential candidate for polymer electrolytes. The complexation effect of salt and plasticizer in polymer host electrolytes had been investigated using FTIR. The carbonyl stretch of MG30 locates at 1729 cm−1, with the addition of lithium trimethanesulfonate (LiCF3SO3) salt, new band evolves at lower frequency region at 1643–1645 cm−1. The nondegenerate vibrational mode of νs(SO3) of salted electrolytes appearing at 1031–1034 cm−1 comes from ‘free’ trimethanesulfonate anions and the 1040–1046 cm−1 absorption from the monodentate ion paired with triflates. These indicate MG30–salt interaction. When MG30 and ethylene carbonate (EC) formed film, the CH3 asymmetric bend of MG30 appearing at 1447 cm−1 is shifted to 1449 cm−1 in the EC–polymer complex. The CO stretching at 1729 cm−1 also shifted to 1728 cm−1. Hence, the EC–MG30 system is complexed to each other. EC–LiCF3SO3 interactions are indicated by the shifting of CO bending band of EC from 718 cm−1 being shifted to 720 cm−1 in the complex. In Li+–EC interaction where the ring breathing region at 897 cm−1 in EC has shifted to 899 cm−1 in EC–salt spectrum. The band appearing at 1643–1645 cm−1 due to the coordination of Li+ ← O–C is still under observation and new peaks at 1779 and 1809 cm−1 are responsible to the carbonyl stretches of EC in plasticized salt–polymer electrolytes.