(91c) Chemically Modified Lignin Surfactant: Synthesis, Characterization and Their O/W Interfacial Properties

Lignin-based surfactant was prepared through chemical modification. This bio-based surfactant demonstrated to be a good emulsifier for W/O emulsion. Herein, grafting of butyric anhydride (BA), 3-(trimethoxysilyl)propyl methacrylate (MPS) and 2-bromoisobutyryl bromide (BIBB) onto kraft lignin to change its amphiphilicity was conducted. The chemical reactions were confirmed by FTIR, ¹H NMR, GPC, TGA analysis, and ³¹P NMR. Lignin modified with MPS and BIBB could only dissolve partially in organic monomer due to the low grafting ratio. In contrast, over 95% of the hydroxyl group conversion was achieved when butyric anhydride was used. The butyric anhydride modified lignin resultant (lignin-B) was found to be completely soluble in oil monomers. According to the interfacial tension measurement, lignin-B was able to decrease the interface energy between water and styrene from 35 J·m^-2 to 15 J·m^-2. As expected, stable water-in-oil emulsion was prepared with lignin-B as emulsifier. The average diameters of emulsion droplets were 499.4 nm and 363.9 nm with a lignin-B content of 0.5 wt % and 5 wt % respectively. No separated aqueous phase was observed for 30 days. These results suggest lignin-B has promising potential to be used as a bio-based surfactant or emulsifier.