Completely Miscible Polymer Blend Electrolyte Studied by Small-Angle Neutron Scattering

We studied blend electrolytes comprising poly(ethylene oxide) (PEO), poly(pentyl malonate) (PPM), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). Ion transport in the blend electrolytes resembles transport in PEO/LiTFSI and PPM/LiTFSI systems. The thermodynamic properties of the PEO/PPM/LiTFSI blend electrolytes were studied by small-angle neutron scattering (SANS). The effect of added salt on polymer blend thermodynamics is quantified by an effective Flory–Huggins interaction parameter, χeff. The blend electrolytes exhibit one-phase, and χeff is negative at all salt concentrations. This is noteworthy because the addition of salt generally leads to macrophase-separation in polymer blends.