Abstract
We investigate the effect of alcohol fraction (isopropanol, IPA) in a binary water-alcohol solvent mixture on the shear and extensional rheological properties, as well as the role of viscoelasticity on fiber formation of poly(acrylic acid) (PAA) in electrospinning. Comparison of the scaling of both specific viscosities ηsp and extensional relaxation times λE of PAA in water–IPA mixtures, showed stronger scaling compared to salt-free aqueous polyelectrolyte solutions, except for the ηsp in the unentangled regime displaying a polyelectrolyte-like scaling ηsp ~ c0.5 for all IPA%. Such deviation suggested IPA induces association/aggregation of PAA. However, the trends between ηsp and λE magnitudes as a function of IPA% differ for concentrations compared in the entangled regime. The ηsp as well as their elastic moduli exhibit a maximum, whereas λE increases monotonically with IPA%, suggesting a complex interplay of various interactions are dictating their structure in water-IPA mixtures, affecting their shear and extensional response differently. Electrospinning experiments showed increasing IPA% reduces the onset of both beaded and uniform fibers. Analysis using dimensionless numbers indicated the enhancement of their elasticity by IPA, and the consequent stabilizing effect on their jets/filaments against break-up during electrospinning, plays a role in the improvement of their fiber formation.
