Structure, molecular dynamics, and conduction mechanism of chitosan/[BMIM][TfO] ionic liquid composites

The current study presents a comprehensive investigation into the structural, thermal, and dielectric properties of chitosan (Cs) composite films modified with the ionic liquid (IL) 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([BMIM][TfO]) at concentrations ranging from 10 to 70 wt%. The incorporation of IL induced a significant morphological transition from compact semi-crystalline structures to vertically aligned porous nanostructures as demonstrated by SEM and AFM. XRD and FTIR analyses revealed reduced crystallinity and the formation of new hydrogen bonding interactions between IL and Cs. Thermal analysis (TGA/DTG, DSC) showed a multi-step degradation, reduced glass transition temperatures (T_g), and the emergence of additional thermal events associated with cold crystallization/domain ordering at higher IL contents, reflecting the dual role of IL as plasticizer and structural modulator. Dielectric spectroscopy (DS) exhibited a single β-relaxation attributed to restricted local side-chain dynamics, which speed up with increasing the IL content due to the plasticization effect of IL on polymer chains. DC conductivity (σ_dc) followed Arrhenius temperature dependence with decreasing activation energy (102.08-37.69 kJ/mol), consistent with thermally activated hopping described by the correlated barrier hopping (CBH) model.