Fluidic lignin with ultra-low glass transition temperature (Tg < −57 °C): a versatile polyelectrolyte solvent platform

Abstract

Polyelectrolytes with ultra-low glass transition temperatures (T_g) are still a rarity. Herein, we report a series of free-flowing lignin polyelectrolytes with ultra-low T_g in the range of −57–9 °C, namely, deep eutectic supramolecular lignin (DESL). The enabling key principle is to couple the eutectic strategy with supramolecular polymerization, bypassing the exclusive reliance on the large size and flexible cation/anion pairs for flowable polyelectrolytes. Following this principle, various sugars have been successfully integrated with lignosulfonic acid via multiple hydrogen bondings, allowing for bulk yet free-flowing supramolecular materials. These DESLs are processible, adaptive, and compatible to serve as macromolecular solvents and are distinct from traditional polyelectrolyte solutions or chemical modification derivatives. The robustness and versatility of our approach provide a fresh opportunity for booming polyelectrolyte utilization, opening access to a yet unknown fluidic material class.