Selective localization of lithium trifluoromethanesulfonate in the blend of hexanoyl chitosan and polystyrene

Abstract

The miscibility of hexanoyl chitosan and polystyrene blend at 80:20 composition was investigated using dilute solution viscometry (DSV) and differential scanning calorimetry (DSC) methods. Viscometric and thermal analysis showed that hexanoyl chitosan and polystyrene are immiscible. Polymer electrolytes based on hexanoyl chitosan and polystyrene blend (80:20) were prepared using lithium trifluoromethanesulfonate (LiCF₃SO₃) as the doping salt. Fourier transform infrared (FTIR) study on polystyrene-LiCF₃SO₃ suggested that there is no interaction between polystyrene and LiCF₃SO₃. LiCF₃SO₃ interacted with hexanoyl chitosan to form Li⁺-hexanoyl chitosan complexes. DSC results revealed that the glass transition temperature (T _g) of hexanoyl chitosan in the blend increases with increasing salt concentration, whereas the T _g of polystyrene in the blend remains constant. FTIR and DSC results thus suggested the selective localization of LiCF₃SO₃ in hexanoyl chitosan phase in the blend. The dependence of conductivity with salt concentration is found to be in agreement with the variation of the spectroscopically free form of ${\mathrm{C}\mathrm{F}}_3{\mathrm{S}\mathrm{O}}_3^{-}$ .