Amphiphobic meta-aramid nanofiber mat with improved chemical stability and mechanical properties

Abstract

Electrospun meta-aramid nanofibers are typically extremely vulnerable to dipolar aprotic solvents, such as DMAc, DMSO, and DMF. This low chemical stability has made practical application of such nanofibers difficult. In this work, meta-aramid nanofiber mats with a directional nature were electrospun and sequentially post-treated by salt removal and heat treatment to enhance chemical stability. The salt added to dissolve the meta-aramid in the solvent was completely removed from the meta-aramid nanofibers via repetitive washing. The salt removed meta-aramid nanofiber mat displayed a glass transition behavior not observed in the pristine nanofiber mat. The crystalline structure of the salt-removed nanofiber mats was regenerated by heat treatment above its glass transition temperature, whereas heat-treated nanofiber mats with salt remained amorphous. The salt between the meta-aramid chains interrupted their rearrangement, indicating that, in the absence of salt, the chains could be arranged during heat treatment. Additionally, the sequential post-treatment induced the reforming of intermolecular hydrogen bonds between the chains; thus, the post-treated nanofiber mat exhibited enhanced mechanical and chemical stabilities, which was confirmed by survival of the meta-aramid nanofiber in DMAc. Furthermore, a surface-modified meta-aramid nanofiber mat showing hydrophobicity and superoleophobicity was fabricated by silanization with trichloro (1H,1H,2H,2H-perfluorooctyl) silane.