AbstractNafion, an ionomer composed of perfluorocarbon backbone and vinyl ether side chains terminated with -SO3 - groups, has dual solubility parameters, i.e. δ1= 9.7 (cal/cm3)1/2 relating to perfluorocarbon backbones and δ2 = 17.3 (cal/cm3)1/2 relating to sulfonated vinyl ether side chains. It had been reported that Nafion molecules aggregated in dilute and semi-dilute water and alcohol solutions. In this study, we report static light scattering (SLS) measurements of dilute Nafion in N,N’- dimethyl formamide (DMF, solubility parameter δ =12.2 (cal/cm3)1/2, dielectric constant ε=36.7) and N,N’-dimethyl acetamide (DMAc, δ =10.8 (cal/cm3)1/2, ε=37.8) solutions with Nafion concentrations ranging from 0.2 mg/ml to 1.0 mg/ml. The DMF and DMAc solvents have δ closing to δ1 of Nafion perfluorocarbon backbones and ε much lower than water (ε =78). Thus DMF and DMAc are compatible with Nafion perfluorocarbon and few Nafion molecules aggregate in DMF and DMAc solvents when [Nafion]< 1.0 mg/ml. The lower ε of DMF and DMAc led to low polyelectrolyte effect of Nafion in these two solvents. The obtained Mws of present work were in good agreement with the Mw obtained from Nafion in dilute dimethyl sulfoxide (DMSO, δ =12.0 (cal/cm3)1/2, ε=46.6) solutions, reported by Lousenberg, using size exclusion chromatography incorporating static light scattering detection. The <RG> data obtained from SLS measurements were compared with the particles sizes of transmission electron microscope (TEM) observations of freeze dried Nafion thin films prepared on copper grids with 0.6 mg/ml Nafion solutions. Comparable results were obtained from these two observations.
Gas Permeability of Star-Shaped Diblock Copoly(vinyl ether)s with Oxyethylene Side Chains