Development of PEG-grafted-lignosulfonate/cationic-polyelectrolyte/poly(acrylic acid) complex and evaluation of its toughness, self-healing property, and internal physical structure

Abstract

A lignosulfonate-derived material was prepared by complexing polyethylene glycol (PEG)-grafted lignosulfonate (LS-g-PEG) with a cationic polyelectrolyte (PDADMACl). The mechanical property of this LS-g-PEG/PDADMACl complex was similar to those of the conventional unmodified-LS/PDADMACl complex, however, the addition of poly(acrylic acid) (PAAc) improved the toughness of the LS-g-PEG complex more than seven-fold at the optimal composition (from 0.7 to 5.2 MJ/m3). This increase in toughness upon PAAc addition was not observed in the conventional unmodified-LS/PDADMACl complex and it was attributed to the synergistic effect of plasticization by the amorphous PEG component, as well as the formation of a rigid polyelectrolyte complex. In addition to better strain and toughness than other reported lignosulfonate-derived materials, the LS-g-PEG/PDADMACl/PAAc complex displayed a humidity-induced self-healing property; complete healing of mechanical properties was observed under optimal conditions. These good toughness and excellent self-healing properties may broaden the applications of lignin-derived materials as highly durable and damage-resistant materials.