Nanofiber engineering of microporous polyimides through electrospinning: Influence of electrospinning parameters and salt addition

Abstract
The electrospinning of high-performance polyimides (PI) has recently sparked great interest. In this study, we explore the effect of the electrospinning parameters — namely polymer concentration, voltage, tip-to-collector distance and flow rate — and salt addition on the diameter, morphology, and spinnability of electrospun PI nanofibers. Three different polyimides of intrinsic microporosity (PIM-PIs) with high Brunauer–Emmett–Teller (BET) ranging from 270 to 506 m2 g−1, and two microporous polyimides, were synthesized through the polycondensation of 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and aromatic diamines. The addition of tetraethylammonium bromide (TEAB) salt considerably increased the conductivity of all the PI solutions, significantly improved spinability, and resulted in thinner fibers. We also used molecular dynamic simulations to investigate the macromolecular mechanism of improved spinnability and fiber morphology in the presence of an ammonium salt. The small droplets detached from the parent droplet, followed by the rapid evaporation of the ions through the hydration effect, which facilitated the electrospinning. The resulting uniform nanofibers have great potential in environmental applications due to the presence of microporosity and hydrophobic pendant trifluoromethyl groups, which enhance the sorption performance of the fibers for hydrophobic species.

Citation
Topuz, F., Abdulhamid, M. A., Holtzl, T., & Szekely, G. (2021). Nanofiber engineering of microporous polyimides through electrospinning: Influence of electrospinning parameters and salt addition. Materials & Design, 198, 109280. doi:10.1016/j.matdes.2020.109280

Acknowledgements
The postdoctoral fellowship from King Abdullah University of Science and Technology (KAUST) is gratefully acknowledged (FT). The research reported in this publication was supported by funding from KAUST. This work was supported by the VEKOP-2.1.1-15-2016-00114 project, which is co-financed by the Hungarian Government and the European Union.

Publisher
Elsevier BV

Journal
Materials & Design

DOI
10.1016/j.matdes.2020.109280

Additional Links
https://linkinghub.elsevier.com/retrieve/pii/S0264127520308157

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