Dynamics and nanolevel structure in an ionomer blend of two polymers with widely separated glass transitions

A new ionomer blend of zinc-neutralized sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) and an amino silicone copolymer was prepared. The blend precipitates as a gel from dilute solution and forms a coherent film. Magic angle spinning carbon-13 spectra indicated coordination of the amine of the amino silicone copolymer by the zinc ion. Differential scanning calorimetry and dynamic mechanical spectra show a smearing out of the glass transition over the more than 300 deg temperature separation of the glass transitions of the component polymers. Solid-state proton NMR line shapes indicate narrowing commences at -115 degrees C, but then the line remains a composite of a narrow Lorentzian line and a broad Gaussian line for at least the next 200 deg, in agreement with the dynamic mechanical data. Goldman-Shen proton spin diffusion measurements give a domain size of the order of 30 Angstrom, corresponding to the more mobile protons contributing to the Lorentzian line shape component. Silicon-29 chemical shift anisotropy line shapes demonstrate the onset of mobility for some of the siloxane units beginning at -115 degrees C, but complete line shape collapse does not occur even after a 200 deg temperature rise. This again indicates an extended glass transition process even when considering just one component of the blend.