Synergistic effects in cross-linked blends of ion-conducting PEO-/PPO-based unsaturated polyesters
AbstractIon-conductive unsaturated polyesters (UP) were synthesised from poly(ethylene oxide) (Xn = 9, 13, 22, 90) or poly(propylene oxide) (Xn = 7, 13, 20, 34, 68) and maleic anhydride. Subsequently, the polyesters were doped with LiClO4 and cross-linked with styrene using a redox initiator. For PEO-based polyesters, the minimum resistivity is found at an O/Li+ molar ratio of 50/1. In contrast, more lithium is required to reach the minimum when using PPO (O/Li+ = 10/1). Unlike the PEO-based polyesters, cross-linking of the PPO types gives rise to decreasing resistivities at increasing molecular weight. This correlates well with the transverse proton relaxation time determined by single-sided NMR, which is an indicator of the chain mobility. The cross-linking reaction of these UP with styrene exactly follows the predictions based on the copolymerisation parameters and is, therefore, not dependent on the ratio of styrene to UP double bonds as previously reported. Due to the opposing effects of the molecular weight on the ion conductivity of PEO- and PPO-based UP, 1:1 blends of short-chain PPO and long-chain PEO polyesters were cross-linked with styrene. The resulting networks showed a resistivity of 4 kΩ m (σ = 2.5∙10−4 S∙m−1), which is 5 times lower than the pure PEO and 3 times lower than the pure PPO materials.
