Abstract
Physical properties of pre-electrospinning polymer solutions play a key role in electrospinning as they strongly determine the morphology of the obtained electrospun nanofibers. In this work, an atmospheric-pressure argon plasma directly submerged in the liquid-phase was used to modify the physical properties of poly lactic acid (PLA) spinning solutions in an effort to improve their electrospinnability. The electrical characteristics of the plasma were investigated by two methods; V-I waveforms and Q-V Lissajous plots while the optical emission characteristics of the plasma were also determined using optical emission spectroscopy (OES). To perform a complete physical characterization of the plasma-modified polymer solutions, measurements of viscosity, surface tension, and electrical conductivity were performed for various PLA concentrations, plasma exposure times, gas flow rates, and applied voltages. Moreover, a fast intensified charge-couple device (ICCD) camera was used to image the bubble dynamics during the plasma treatments. In addition, morphological changes of PLA nanofibers generated from plasma-treated PLA solutions were observed by scanning electron microscopy (SEM). The performed plasma treatments were found to induce significant changes to the main physical properties of the PLA solutions, leading to an enhancement of electrospinnability and an improvement of PLA nanofiber formation.
Highlights
Shi et al.[6,21] used a capacitively-coupled helium dielectric barrier discharge to treat polyethylene oxide (PEO) and Ag/polyacrylonitrile (Ag/PAN) solutions and observed that the polymer solution viscosity, conductivity, and surface tension increased after plasma treatment and finer and smoother nanofibers were formed with fewer microbeads and increased crystallinity
The work presented in this paper will be novel as it intends to employ an atmospheric-pressure plasma jet directly submerged into the polymer solution
The argon plasma will be examined in detail making use of optical emission spectroscopy (OES) and electrical measurements while the plasma bubble dynamics will be investigated using an intensified charge-couple device (ICCD) camera system
Summary
Shi et al.[6,21] used a capacitively-coupled helium dielectric barrier discharge to treat polyethylene oxide (PEO) and Ag/polyacrylonitrile (Ag/PAN) solutions and observed that the polymer solution viscosity, conductivity, and surface tension increased after plasma treatment and finer and smoother nanofibers were formed with fewer microbeads and increased crystallinity These authors studied the effects of plasma exposure time and polymer concentration on the final electrospinnability of the solutions. The present work systematically investigate the effects of this directly submerged plasma treatment on the physical properties of the pre-electrospinning polymer solutions and on the final morphology of the produced nanofibers considering various operational parameters including polymer concentrations, applied voltage, gas flow rate, and plasma treatment time. In a final step, untreated and plasma-modified PLA solutions will be electrospun after which the resultant nanofiber morphology will be studied using scanning electron microscopy (SEM)
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