(33b) Stringiness, Spinnability and Extensional Rheology of Entangled Polymer Solutions

Designing application-ready fibers involves multifaceted challenges related to correlating the formulation properties and processing parameters to the fiber engineering trifecta of spinnability, morphology, and properties. Here, we characterize the influence of macromolecular and solvent properties on the trifecta for polyvinylpyrrolidone (PVP) and poly(ethylene oxide) or PEO fibers produced using a bespoke centrifugal force spinning (CFS) set-up and matched processing parameters. We illustrate the influence of changing solvent on spinnability, morphology, and properties (thermal and mechanical) by varying acetonitrile (AcN) fraction in the spinning dope formulated with PEO dissolved in AcN:H₂O mixtures, and varying ethanol in dope formulated with PVP dissolved in Ethanol:H2O mixtures. We characterize rheology and stringiness using shear and extensional rheology characterization. Furthermore we contrast the numerical values of measured diameter, tensile strength, elongation-at-break, and crystallinity of centrifugally spun fibers with the published datasets for electrospun fibers using the Berry number (or the overlap parameter) as the ordinate. We compile, analyze, and replot ES and CFS spinning datasets obtained for various solvents, polymer (M_w and c), and processing parameters. Even though distinct forces determine the jet trajectory and fiber formation for ES and CFS, we find centrifugally spun fibers emulate electrospun fiber properties, morphology, and spinnability. We present the mechanism underlying volatile-entangled (VE) spinnability, displayed here by PVP and PEO solutions in certain solvent mixtures.