The Impact Of Ionic Liquid On Morphology And Structure Of Electrospun Fibers

Ionic liquid (IL), comprised of an organic anion and an organic or inorganic anion, aresalts that exist in the liquid state at or close to room temperature. Due to their low vaporpressure, chemical stability, thermal stability, and high ionic conductivity properties, they arewidely used in environmental, chemical, biological and other fields. Additionally,excellent dissolution properties and environmental friendliness of IL can broadenthe range of spinning polymer in electrospinning, hence, it has great value toeffectively promote the development of electrospinning by introducing IL.The impact of IL on properties of PAN/DMF solutions was investigated. Wedemonstrated that with the amount of IL increased from0.1%(g/ml) to1%mol/L, electricconductivity of PAN/DMF solutions significantly increased, while surface tension andviscosity did not correlate directly to it. The electric conductivity decreases with the reductionin the size of inorganic anions or with the increase in the carbon chainlength of the organic cation. The electric conductivity of PAN/DMF solutions with differentIL down as follows:(EMIM)3PO4>EMIMBr>C4MIMCl>C12MIMCl.We found IL have a significant effect on morphology of the electrospun PAN fibers, thatis, crystallization of IL makes the smooth surface of fibers into a rough structure.With the amount of IL increased, the diameter of fibers oscillatory decreased to the minimumthat has a correlation with the structure of IL, and then increased. The diameter of PAN/(EMIM)3PO4composite fiber produced from high ionic conductivity solution decreased to theminimum at a relative low amount of IL (2.5%mol/L), while PAN/DMF/EMIMBr at8mol/L.Due to the similarity of ion mobility, both PAN/EMIMBr and PAN/C4MIMCl compositefiber decreased to the minimum at5mol/L. And thinner fibers have more uniform distribution.The impact of ionic liquid (C4MIMCl) on structure of electrospun PVDF/PANcomposite fibers was also investigated. With the addition of C4MIMCl, the structure ofPVDF/PAN bicomponent fibers changed from core-sheath structure to eccentric structure andeven to side-by-side structure in high voltage electric field. With the concentration ofC4MIMCl and voltage increased, much more apparent phenomenon can be observed.