We studied the conducting and mesomorphic behavior of a dendritic-linear copolymer on adding hydrophilic additives and lithium salts. For the preparation of the pristine block copolymer (A), a click reaction of a hydrophobic Y-shaped dendron block and a hydrophilic linear poly(ethylene oxide) coil with M(n) = 750 g mol(-1) was performed. For ionic block copolymer samples (1-3), a hydrophilic compound (B) bearing two tri(ethylene oxide) chains was used as the additive. In all ionic samples, the lithium concentration per ethylene oxide was chosen to be 0.05. As characterized by polarized optical microscopy and small angle X-ray scattering techniques, copolymer A showed a hexagonal columnar mesophase. On addition of lithium-doped additives, ionic samples 1 and 2 with the additive weight fractions (f(w)) of 10 and 20%, columnar and bicontinuous structures coexisted in the liquid crystalline phase. On the other hand, ionic sample 3 with f(w) = 30% displayed only a bicontinuous cubic mesophase. Based on the impedance results, with increasing the amount of additives, the conductivity value increased from 3.80 x 10(-6) to 2.34 x 10(-5) S cm(-1) at 35 degrees C. The conductivity growth could be explained by the interplay of the plasticization effect of the mobile additive and the morphological transformation from 1D to 3D of the ion-conducting cylindrical cores. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 24682473, 2011