Investigation of electrochemical properties of lithium salt/poly(vinylidene fluoride)/polypyrrole blends

Abstract In this study, structural, thermal, morphological, and electrochemical properties of poly(vinylidene fluoride)/polypyrrole (PVDF/PPy) blends are investigated. The investigation revealed phase separation between PPy and PVDF, a phenomenon supported by the thermodynamic interaction parameter. Increasing the PPy content from 10 to 50 wt% led to a significant reduction in the crystallinity of PVDF from 55.1% to 39.6%, and a corresponding decrease in the glass transition temperature ( T g ) from 52.2 to 42.3°C. The enhanced interaction between components in the PVDF/PPy blends leads to an increase in local free volume due to the disruption of the polymer matrix. This disruption allows for greater molecular mobility, which in turn decreases the T g . The increase in local free volume facilitates segmental motion of the polymer chains, thereby reducing the energy required for the transition from a glassy to a rubbery state. Ionic conductivity of the blends decreased with rising temperatures, likely due to interactions between the fluorine groups of PVDF and the NH groups of PPy. Notably, the transference number of lithium ions ( t Li+ ) decreased from 0.30 to 0.14 as the PPy content increased from 10% to 50%, indicating a strong interaction between the cation and the polymer matrix. Highlights Electrochemical properties of poly(vinylidene fluoride)/polypyrrole (PVDF/PPy) blends are investigated. Interaction parameter‐supported phase separation is seen between PPy and PVDF. Intramolecular interactions of PVDF result in increasing local free volume. Ionic conductivity of the blends decreased with rising temperatures. t Li+ decreased with PPy increasing due to strong interaction of cation/matrix.