Local Free Volume and Structure of Polymer Gel Electrolytes on the Basis of Alternating Copolymers

The relationship between the structure of the polymer and the charge carrier mobility and the ionic conductivity has been studied for a new class of gel electrolytes on the basis of alternating copolymers. These gel electrolytes were prepared by photopolymerization of maleic anhydride and oligo(ethylene glycol)4 divinyl ether in the presence of various oligo(ethylene glycol)n dimethyl ethers with molar masses between 134 and 2000 g/mol, and LiCF3SO3. Thermal properties of the materials were studied by differential scanning calorimetry and dynamic mechanical analysis, which additionally gives structural information. Changes in the free volume as a function of the content of the plasticizer and the salt were studied by positron annihilation lifetime (PAL) spectroscopy. The self-diffusivity of charge carriers and plasticizer in the gel electrolytes was investigated by pulsed field gradient NMR. The ionic conductivity and its pressure dependence were determined by the impedance technique. The gel electrolytes...