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

Hard–soft–hard triblock copolymers based on poly­(ethylene oxide) (PEO), poly­(2-naphthyl glycidyl ether)-<i>block</i>-poly­[2-(2-(2-methoxy­ethoxy)­ethoxy)­ethyl glycidyl ether]-<i>block</i>-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 (<i>f</i><sub>wt,PNG</sub> = 9.2–28.6 wt %), controlled molecular weights (<i>M</i><sub>n</sub> = 23.9–30.9 kDa), and narrow dispersities (<i>Đ</i> = 1.11–1.14). Most of the PNG-PTG-PNG electrolytes had much higher Li<sup>+</sup> conductivities than that of a PEO electrolyte (6.54 × 10<sup>–7</sup> S cm<sup>–1</sup>) at room temperature. Eespecially, the Li<sup>+</sup> conductivity of PNG<sub>18</sub>-PTG<sub>107</sub>-PNG<sub>18</sub> electrolyte (9.5 × 10<sup>–5</sup> S cm<sup>–1</sup> for <i>f</i><sub>wt,PNG</sub> = 28.6 wt %) was comparable to one of a PTG electrolyte (1.11 × 10<sup>–4</sup> S cm<sup>–1</sup>). The Li<sup>+</sup> conductivities of PNG-PTG-PNG electrolytes were closely correlated to efficient Li<sup>+</sup> transport channels formed by the microphase separation into soft PTG and hard PNG domains.