Sequential effect and enhanced conductivity of star-shaped diblock liquid-crystalline copolymers for solid electrolytes

Star-shaped polymers are synthesized by atom transfer radical polymerization using poly-(methoxy-poly (ethylene glycol) methacrylate) (PPEGMA) as a hydrophilic segment and poly (10-[(4-cyano-4'-biphenyl) oxyl decatyl methacrylate} (PMALC) as a hydrophobic liquid crystalline segment. Lamellar morphology is also achieved by cooperative assembly of hydrophobic mesogen-containing polymethacrylates and the amorphous hydrophilic PPEGMA nanoscale aggregation, especially after liquid crystal thermal annealing. In addition, the sequential effect, that is, the position difference of the liquid crystalline segments in the copolymer electrolytes causes two quite different morphologies. The liquid crystalline segments arranged in the star polymer inner sphere makes it difficult for the mesogens to interact with each other efficiently, which leads to a discontinuous molecular packing. However highly ordered domains can be formed in the electrolytes with mesogens in the star copolymer exterior, which can provide a more favorable morphology for the ions transportation. As a result, incorporation of the liquid crystalline segments into the copolymer has improved ionic conductivity of electrolytes, especially for the 3PPEGMA-PMALC with the mesogen arranged in the outside of star copolymer sphere. Ionic conductivity of 3PPEGMA-PMALC annealed at liquid crystalline state is 1.0 x 10(-4) S cm(-1) at 25 degrees C, which is higher than that of 3PPEGMA electrolytes without mesogen groups. (C) 2013 Elsevier B.V. All rights reserved.