Fluorescent solvent-free lignin ionic complexes with thermostability toward a luminescent hydrophobic coating material

Abstract

Lignin is one of the abundant natural biomass resources. Developing lignin into fluorescent materials is gaining continuous attraction. In this study, a type of fluorescent lignin ionic complexes (LS-TPEA) is developed via the electrostatic complexation between ligninsulfonate and a tetraphenylethene-containing ammonium surfactant. The solvent-free LS-TPEA materials show thermotropic liquid crystal properties, and could exhibit blue luminescence under UV light. The fluorescence emission of LS-TPEA relies on the ordered structure, which could be turned off by forming isotropic liquid. The good thermostability allows LS-TPEA to be recyclable labeling biomaterials suitable for working at high temperatures, and by taking advantage of the water-resistance properties LS-TPEA would also be good hydrophobic fluorescent coating materials. This work provides a designing strategy for fabricating fluorescent lignin materials, facilitating the value-added utilization of lignin resources.