Synthesis of crown ether polymers incorporating 12- and 13-membered tetraoxa rings linked to poly(propylene oxide) and poly(phosphazene) backbones and behaviour of the lithium-doped materials

Abstract

The synthesis of a set of 12- and 13-membered crown ether polymers is reported. An oxyethylene chain separates the macrocyclic ring from either a poly(propylene oxide) or a poly(phosphazene) backbone. Addition of Li⁺ ions to these amorphous polymers and the related poly(methacrylate) polymers results in increases in T_g and the 12-O₄ polymers show the largest increases. This behaviour is correlated with changes in the ¹³C NMR spectra of the polymers as Li⁺ is added, and the relative sensitivity of the 12-O₄ polymers is related to their enhanced tendency to form 2 : 1 complexes (ring : Li⁺). Parallel observations were found on examination of the ionic conductivities of the lithium-doped materials with the 13-O₄ polymers showing lower conductivities and in the polypropylene oxide-based polymers the backbone did not contribute significantly to the overall charge transport.