Synthesis of Well-defined Block Copolymer Electrolytes Using Atom Transfer Radical Polymerization

A series of well-defined hydrophobic-hydrophilic di-blocks has been synthesized under environmentally friendly conditions through atom transfer radical polymerization (ATRP). The hydrophilic block is based on methoxy-capped oligo(ethylene glycol) methacrylate (nEGMA, n = 4∼5, 8∼9) and the hydrophobic component is PMMA block. ATRP prepared PMMA-Br (Mn 12000 Mw/Mn 1.37) was applied as a macroinitiator. Two solvent systems, acetone and mixed solvents of toluene/H2O (1/10), were employed. The acetone mediated polymerization gave the copolymer good control of molecular weight distribution (1.2) and rapid conversion. The toulene/H2O mediated polymerization provided the copolymer with a higher molecular weight but a less narrow polydispersity. The maximum conductivity was measured as 4.8 × 10−5 S/cm at 90 °C with di-block coplymer, (PMMA)x-b-(PnEGMA)y (n = 8∼9, x/y ratio 3/1, contained ∼67 wt.% PEGMA), doped with Li salt ([EO:Li+] = 20:1). The conductivity at room temperature was ca 2 × 10−6 S/cm.