How does counter-cation substitution influence inter- and intramolecular hydrogen bonding and electrospinnability of alginates

Despite numerous applications of nanofibrous alginate (Alg) mat, its facile fabrication via electrospinning is still challenging. The low alginate content compared to the carrier polymer and existence of impurities are the main drawbacks of existing approaches. The purpose of this research is both to study and improve alginate electrospinnability by focusing on the effect of inter- and intramolecular hydrogen bonding. Based on hard and soft acids and bases (HSAB) theory, the Na+ cations (carboxylate counter-cation) were substituted with a harder acid, Li+ cation, to increase the strength of ionic interaction and decrease the density of hydrogen bonding. Viscosity and electrical conductivity measurements as well as FTIR and H-1 NMR revealed a lower intramolecular hydrogen bonding density in Li-Alg. SEM images showed improvement of alginate electrospinnability for Li-Alg compared to the salts of Na-Alg and K-Alg. This study sheds more light on underlying reasons hindering alginate electrospinning and introduces a simple method for fabrication of nanofibers with high alginate content. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This research aims to improve the electrospinnability of alginate by focusing on the effect of inter- and intramolecular hydrogen bonding, using Li+ cation to reduce the hydrogen bonding density. Viscosity, electrical conductivity, FTIR, and H-1 NMR measurements confirmed the lower intramolecular hydrogen bonding density in Li-Alg. SEM images demonstrated the enhanced electrospinnability of Li-Alg compared to Na-Alg and K-Alg salts.