Conductivities and Spectroscopic Studies of Polymer Electrolytes Based on Linear Polyurethane and Hybrid and Copolymer of Linear and Hyperbranched Polyurethanes

Three polyurethane electrolytes, linear polyurethane (LPU), hybrid of linear and hyperbranched polyurethane (MHPU), and low cross-linked copolymer of linear and hyperbranched polyurethane (CHPU) complex with LiClO 4, were studied using conductivity, FTIR, Raman, and 13 C, 1 H, and 7 Li solid-state NMR measurements. The best conductivity value measured at 25 °C was 2.7 × 10 -7 S cm -1 at about a EO/Li ratio of 8 for the LPU electrolytes. At a higher salt concentration (EO/Li = 4), the MHPU and CHPU electrolytes reached its maximum conductivity, 1.35 × 10 -6 and 1.51 × 10 -5 S cm -1, respectively. FTIR, Raman, and 13 C NMR analysis showed that hyperbranched polymer could function as a “solvent” for the lithium salt. Correlation times and the activation energies for the polymer segmental and the lithium hopping motions were determined from the temperature dependence of the spin−lattice relaxation of the polymer ( 1 H) and lithium ( 7 Li). The correlation time and activation energy for the lithium hopping motions in the CHPU electrolytes had a relatively low value. This indicated that lithium ion transport was easier in such a system.