Ion States and Transport in Styrenesulfonate Methacrylic PEO9 Random Copolymer Ionomers

Abstract

Random ionomers based on methacryl poly(ethylene oxide) with nine ethylene oxide units on the side chain and sodium sulfonated styrene (NaSS) are synthesized by reversible addition–fragmentation chain transfer polymerization. The glass transition temperature increases gradually as ions are incorporated at low ion content then more strongly as the ion content reaches 51 mol % NaSS comonomer (1:9 ion to ether oxygen (EO) ratio), exceeding the polarizability volume overlap for contact pairs at 35 mol % NaSS comonomer. Ionomers with 51 and 70 mol % NaSS comonomer show microphase separation, as determined by X-ray scattering, where ion-rich microphases have glass transition temperature Tg = 165 °C excluding many of the PEO side chains, which primarily reside in a dilute ion-pair microphase. Fourier transform infrared spectroscopy was used to characterize the fraction of sulfonates in three different association states that can be related to the static dielectric constant from dielectric relaxation spectroscopy...