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-alkyloxy-1,3-phenylene)] (polymer I), a copolymer of tetrarnethylene oxide with -(CH2)(12)- segments (polymer II) and lithium salts, either Li(CF3SO3)(2)N (Li TFSI) or a 50150 mixture of LiBF4 and LiCIO4 is described. The DC polarisation of cells Li \I:II:LiX\ Li gives polymer electrolyte conductivities sigma = 10(-4) S cm(-1) at 20 degreesC for TFSI anions, slightly higher than complex impedance measurements (4 x 10(-5) S cm(-1)) for the same system. However, conductivities ca. 10(-2) S cm(-1) at 30 degreesC 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. (C) 2002 Elsevier Science B.V. All rights reserved.