Ionic conductivity and morphology of polymer electrolytes based on a side‐chain liquid‐crystalline polysiloxane containing oligooxyethylene spacers and 6‐cyano‐2‐naphthyl benzyl ether mesogens

Solid polymer electrolytes with different stoichiometries were prepared from solvent‐cast mixtures of alkali metal salts with the side‐chain liquid‐crystalline polysiloxane 2. Differential scanning calorimetry, optical polarizing microscopy, X‐ray diffraction, and conductivity measurements revealed that both morphology and conductivity of the obtained complexes are dependent on the salt content. For the complexes formed from 2 with LiSO3CF3, the formation of a homogeneous phase occurred approximately at the mole ratio LiSO3CF3 to oxyethylene unit of 1/2. The conductivity of the complex gradually increases with increasing mole ratio LiSO3CF3/OCH2CH2. The highest conductivity at ambient temperature achieved was 4,8 · 10−6 S · cm−1, which corresponds to the complex with a mole ratio LiSO3CF3/OCH2CH2 of 1/1. For all complexes obtained the temperature dependence of the conductivity displays an unusual behaviour in the temperature range belonging to the glassy and glass transition states of the polymer and an Arrhenius‐type behaviour in the temperature range belonging to the liquid‐crystalline state of the polymer. For the complexes formed from 2 with various alkali metal salts, the conductivity decreases in the order LiSO3CF3 > LiClO4 > NaClO4 > LiBr > KClO4. This indicates that LiSO3CF3 is more effectively ionized by the oxyethylene units than the other salts.