Solid-State Polymer Electrolytes Based on AB₃-Type Miktoarm Star Copolymers

Miktoarm star copolymers composed of three poly(ethylene oxide) (PEO) arms connected to one polystyrene (PS) chain, i.e., PS-(PEO)₃, demonstrated synergistic improvements in the ionic conductivity and mechanical strength by factors of 2-30 compared to those shown by PS-PEO diblock copolymers. Entropic constraints for the chain stretching of (PEO)₃ gave rise to notably reduced domain sizes of PS-(PEO)₃ electrolytes, compared with the values of PS-PEO analogues. Further, the melting transition of PS-(PEO)₃ with PEO molecular weight of Mn = 2 kg mol⁻¹ was vanished with lithium salt doping at [Li]/[EO] = 0.06 under such confinements, resulting in an order of magnitude increase in the room temperature conductivity. The fact that lithium ion transport in PEO-based copolymers can be tunable by the way PEO chains are connected to hard polymers can lead to innovative designs for solid-state polymer electrolytes.