Ionomers from Step-Growth Polymerization: Highly Ordered Ionic Aggregates and Ion Conduction

Abstract

Precisely controlling the position of ionic groups along neutral polymer backbones in ionomers has led to novel nanoscale morphologies and promising properties, although the synthetic routes can be quite demanding. Here, we report a series of Li+-containing ionomers directly synthesized from step-growth polymerization of commercially available diol monomers (x = 6 or 12) and dianhydride monomers followed by neutralization with various amounts of lithium salts. The results are nearly precise linear polymers wherein nonpolar segments have precisely 6 or 12 methylene groups, as determined by the diol. The functional segment has two carboxylic acid pendant groups and 6–8 backbone atoms depending on the dianhydride addition. From X-ray scattering, these segmented ionomers exhibit well-defined nanostructures in contrast to the conventional random ionomers. The nearly precise nature of these segmented ionomers does not compromise the morphological ordering. The temperature-dependent ionic conductivities exhibit ...