High-pressure conductivity studies of blends of poly(p-phenylene)s with oxyethylene side-chains and lithium salts

High-pressure electrical conductivity studies have been carried out with poly(p-phenylene)s with oxyethylene side-chains (PPP(EO)_x/y), which were blended with LiCF₃SO₃. Measurements were performed at pressures up to 280 MPa and at different temperatures. The influences of salt concentration, side-chain length, temperature, and plasticizer content on the relative conductance and activation volume are investigated. The temperature-dependent conductivity of the sample is non-Arrhenius and exhibits Williams–Landel–Ferry (WLF) behavior. The logarithm of relative conductance for PPP(EO)_x/y/LiCF₃SO₃ decreases almost linearly with increasing pressure but increases with salt concentration and side-chain length. As temperature increases, the activation volume becomes smaller but remains positive for PPP(EO)_x/y/LiCF₃SO₃. At higher salt concentrations and longer side-chain lengths, a smaller activation volume for the ion motion is found. These results can be interpreted such that PPP(EO)_x/y/LiCF₃SO₃ behaves like a true polymer electrolyte where ion transport is mediated by segmental motions of the EO side-chains. The addition of tetraethylene glycol dimethyl ether (TEGDME) as a plasticizer increases the activation volume but reduces the conductance.