Effect of Polymer Architecture on the Ionic Conductivity. Densely Grafted Poly(ethylene oxide) Brushes Doped with LiTf

Densely grafted poly­(ethylene oxide) (PEO) brushes on a poly­(hydroxyl­styrene) (PHOS) backbone (PHOS-g-PEO) as well as block copolymers with polystyrene (PS) (PS-b-(PHOS-g-PEO)) are designed as model systems for Li ion transport. This macromolecular design suppresses the propensity of PEO chains for complex crystal formation with LiTf as well as for crystallization. Li ion conductivities similar or even exceeding those in the archetypal electrolyte poly­(ethylene oxide)/lithium triflate (PEO/LiCF₃SO₃ (LiTf)) are obtained for a range of temperatures and LiTf compositions. At the same time, PHOS-g-PEO and PS-b-(PHOS-g-PEO) show improved mechanical stability. Typically, at 333 K, the ionic conductivity is ∼6 × 10^–5 S/cm and the modulus at ∼2 × 10⁶ Pa for a [EO]:[Li⁺] = 8:1 composition. In the endeavor for suitable solid polymer electrolytes macromolecular architecture seems to play a decisive role.