On the preparation of thin nanofibers of polysulfone polyelectrolyte for improving conductivity of proton-exchange membranes by electrospinning: Taguchi design, response surface methodology, and genetic algorithm

Nanofiber-based ion-exchange membranes display distinctive features in energy applications. Bead formation and diameter of nanofibers determine the characteristics of these structures, which can be controlled by the electrospinning process. However, the electrospinning of polyelectrolytes is challenging due to the existence of ionic groups in the polymer structure. To this end, firstly, synthesis and characterization of hydroquinone-based sulfonated polysulfone with a 40% degree of sulfonation as a characteristic model are performed. To investigate the effect of electrospinning parameters on the morphology and diameter of the nanofiber, the appropriate numbers of experiments are designed using the Taguchi method; polymer solution concentration, voltage, feed rate, and needle to collector distance are considered as the design parameters. The proposed levels by the designed experiment are examined by scanning electron microscopy images. In the next step, the response surface method and the analysis of variance are employed to study the effect of each variable and the effectiveness of the final model. Finally, the parameters are optimized by the Genetic algorithm to gain the possible minimum diameter. Accordingly, the polymer solution concentration is the most effective parameter. Moreover, the electrospun thin bead-free nanofibers with an average diameter of about 97.5 nm are attained. The conductivity measurement (in water and temperature range of 20-100 degrees C) of the nanofibrous mat shows superior values of 0.1105-0.2851 S/cm compared to the dense membrane with a conductivity of 0.0791-0.2201 S/cm. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.