Decoupled Cation Transport within Layered Assemblies in Sulfonated and Crystalline Telechelic Polyethylenes br

We present a set of sulfonated monodisperse telechelic polyethylene ionomers that demonstrate ion transport of metal cations in layered ionic assemblies. These semicrystallineionomers have precisely 48 backbone carbons with a sulfonatedgroup at each end and are fully neutralized by a counterion,C48(SO3X)2(X = Li+or Na+). The morphology of these polymersis characterized by using X-ray scattering, and ionic conductivity is probed by using electrochemical impedance spectroscopy. Thesetelechelic polyethylenes exhibit well-defined ionic layers at alltemperatures below the melting point, and the crystal packing ofthe backbone varies with temperature. The polyethylene backbone packs in hexagonal crystals at high temperatures in bothC48(SO3Li)2and C48(SO3Na)2, with Arrhenius activation energies (Ea) for ion transport of 120 and 53 kJ mol-1, respectively,indicating that decoupled ion transport is possible through these layered ionic assemblies. TheEain this hexagonal regime issignificantly lower thanEaat room temperature where C48(SO3Li)2exhibits disordered crystals and C48(SO3Na)2exhibitsorthorhombic crystallites, highlighting the impact of polymer packing between the ionic layers. At intermediate temperatures (120-160 degrees C) the hexagonal crystal structure in C48(SO3Na)2coexists with an unidentified crystal phase that appears to have superior iontransport properties. When compared to other single ion conductors of the same functionality, C48(SO3Na)2also demonstrates the importance of ionic assembly shape and identifies ionic layers as a promising strategy relative to assemblies with less order