Influence of polymer I–polymer II compatibility on conductivity in low-dimensional polymer electrolyte blends

The preparation of polymer electrolyte blends of the amphiphilic helical poly[2,5,8,11,14-pentaoxapentadecarnethylene(5-a1kyloxy-1,3-phenylene)] (polymer I), a copolymer of tetrarnethylene oxide with –(CH2)12– segments (polymer II) and lithium salts, either Li(CF3SO3)2N (Li TFSI) or a 50/50 mixture of LiBF4 and LiCIO4 is described. The DC polarisation of cells Li|I:II:LiX|Li gives polymer electrolyte conductivities σ=10−4 S cm−1 at 20 °C for TFSI anions, slightly higher than complex impedance measurements (4×10−5 S cm−1) for the same system. However, conductivities ca. 10−2 S cm−1 at 30 °C are observed for the LiBF4–LiClO4 mixture. The higher results for the latter are attributed to more extensive ionic pathways. Furthermore, the use of polymer II incorporating –(CH2)12– segments gives higher results than in their absence. This is attributed to improved blending by interactions between the –(CH2)12– segments and the alkyl sidechains of I.