Electrospinning and solution properties of Nafion and poly(acrylic acid)

In this study, the electrospinning performance and solution properties of Nafion and its blend with another polyelectrolyte, poly(acrylic acid) (PAA), were investigated. Attempts to electrospin pure Nafion at various polymer concentrations (5-35 wt %), solvents, neutralization, and electrospinning conditions resulted in electrospraying rather than electrospinning. However, a polymer solution blend (5 wt %) of Nafion and PAA resulted in beaded fibers at 8 wt % PAA and smooth electrospinning above 12% PAA. Fiber sizes of the blend increased from 90 to 600 nm with increasing PAA content. Dynamic light scattering on pure Nafion solutions in various solvents reveals large aggregates (i.e., dispersion) of various sizes due to polymer backbone and ionic interactions. The lack of sufficient polymer chain entanglement evidenced by low viscosity and aggregate formation in Nafion solutions prohibits fiber formation during electrospinning. The addition of PAA to Nafion modifies the ionic strength of the solvent resulting in suppressed aggregate formation, increased viscosity, and subsequently enhanced polymer chain entanglement. Coincidentally, the onset of suppressed aggregate formation in the blend solution coincides with the electrospraying-electrospinning- transition (8% PAA). In addition, thermal treatment enhances water stability of the electrospun blend fibers.