Synthesis of Hard–Soft–Hard Triblock Copolymers, Poly(2-naphthyl glycidyl ether)-block-poly[2-(2-(2-methoxyethoxy)ethoxy)ethyl glycidyl ether]-block-poly(2-naphthyl glycidyl ether), for Solid Electrolytes

Hard–soft–hard triblock copolymers based on poly­(ethylene oxide) (PEO), poly­(2-naphthyl glycidyl ether)-block-poly­[2-(2-(2-methoxy­ethoxy)­ethoxy)­ethyl glycidyl ether]-block-poly­(2-naphthyl glycidyl ether)­s (PNG-PTG-PNGs), were synthesized by sequential ring-opening polymerization of 2-(2-(2-methoxy­ethoxy)­ethoxy)­ethyl glycidyl ether and 2-naphthyl glycidyl ether using a bidirectional initiator catalyzed by a phosphazene base. Four PNG-PTG-PNGs had different block compositions (f_wt,PNG = 9.2–28.6 wt %), controlled molecular weights (M_n = 23.9–30.9 kDa), and narrow dispersities (Đ = 1.11–1.14). Most of the PNG-PTG-PNG electrolytes had much higher Li⁺ conductivities than that of a PEO electrolyte (6.54 × 10^–7 S cm^–1) at room temperature. Eespecially, the Li⁺ conductivity of PNG₁₈-PTG₁₀₇-PNG₁₈ electrolyte (9.5 × 10^–5 S cm^–1 for f_wt,PNG = 28.6 wt %) was comparable to one of a PTG electrolyte (1.11 × 10^–4 S cm^–1). The Li⁺ conductivities of PNG-PTG-PNG electrolytes were closely correlated to efficient Li⁺ transport channels formed by the microphase separation into soft PTG and hard PNG domains.