Influence of surfactants on the electrospinnability of lignin‑PVP solutions and subsequent oil structuring properties of nanofiber mats

Abstract

This work focuses on the improvement of the electrospinnability of low-sulfonate lignin (LSL)/polyvinylpyrrolidone (PVP) solutions by the addition of surfactants (SDS, CTAB and Tween-20) as well as on the ability of resulting nanofibers to structure castor oil. Solutions with two LSL/PVP weight ratios (70:30 and 90:10) in DMF were prepared by adding variable surfactant concentrations (0–1 wt.%), and physicochemically characterized. Electrical conductivity, surface tension and rheological measurements were performed. Variations of these physicochemical properties were explained on the basis of surfactant-polymer interactions. The addition of surfactants to LSL/PVP solutions improves electrospinnability, producing more compact and uniform fiber mats in 70:30 LSL/PVP systems, generally reducing the average diameter of the nanofibers and the number of beads. In contrast, nanofiber mats were not obtained with 90:10 LSL/PVP solutions, but different nanostructures composed of particle clusters. Dispersions of nanofiber mats obtained by electrospinning from 70:30 LSL/PVP solutions in castor oil were able to generate physically stable strong oleogels. In general, linear viscoelastic functions of oleogels increased with surfactant concentration. In addition, these oleogels exhibited excellent lubrication performance in a tribological contact, with extremely low values of the friction coefficient and wear diameters, which may lead to potential applications as lubricants.