Supercritical Fluid-Assisted Electrospinning of Polymers

In this talk we describe the application of near-critical and supercritical CO$_{2}$ as an electrospinning processing aid to create fibers with novel morphology readily varied by adjusting the operating pressure and temperature. We demonstrate the application of CO$_{2}$ to electrospin poly(vinyl pyrrolidone) (PVP) from PVP-dichloromethane (DCM) solutions. The formation of PVP fibers is directly related to the DCM-CO$_{2}$ phase behavior since the electrospinning operating pressures are well below those needed to dissolve neat PVP in CO$_{2}$. In addition, when spinning into a CO$_{2}$-rich bath, an open-cell fiber morphology is created with features that correlate with the operating pressure. We emphasize in the talk that extreme pressures are not needed to tailor a specific morphology when using CO$_{2}$. The effective removal of the solvent from the polymer solution depends on the partitioning of the liquid solvent between the PVP-rich phase and the CO$_{2}$-rich phase so the thermodynamics of polymer-SCF solvent phase behavior plays a significant role in this process.