FTIR studies of chitosan acetate based polymer electrolytes

Chitosan is the product when partially deacetylated chitin dissolves in dilute acetic acid. As such, depending on the degree of deacetylation, the carbonyl, CONHR band can be observed at ∼1670 cm−1 and the amine, NH2 band at 1590 cm−1. When lithium triflate is added to chitosan to form a film of chitosan acetate–salt complex, the bands assigned to chitosan in the complex and the spectrum as a whole shift to lower wavenumbers. The carbonyl band is observed to shift to as low as 1645 cm−1 and the amine band to as low as 1560 cm−1. These indicate chitosan–salt interactions. Also present are the bands due to lithium triflate i.e. ∼761, 1033, 1182 and 1263 cm−1. When chitosan and ethylene carbonate (EC) are dissolved in acetic acid to form a film of plasticized chitosan acetate, the bands in the infrared spectrum of the films do not show any significant shift indicating that EC does not interact with chitosan. EC–LiCF3SO3 interactions are indicated by the shifting of the CO bending band from 718 cm−1 in the spectrum of EC to 725 cm−1 in the EC–salt spectrum. The Li+–EC is also evident in the ring breathing region at 893 cm−1 in the pure EC spectrum. This band has shifted to 898 cm−1 in the EC–salt spectrum. CO stretching in the doublet observed at 1774 and 1803 cm−1 in the spectrum of pure EC has shifted to 1777 and 1808 cm−1 in the EC–salt spectrum.