The Acetylation of Alkali Lignin and Its Use for Spherical Micelles Preparation

Acetylized modification with acetyl chloride was carried out on alkali lignin (AL) which comes from pulping and papermaking industry, to obtain the acetylated alkali lignin (ACAL). The structural changes between AL and ACAL were characterized by infrared spectroscopy (IR) and nuclear magnetic resonance (NMR), and the results showed that the hydroxy groups in AL were displaced by the acetyl groups in ACAL. ACAL can form spherical micelles which are in the nonoscale by self-assembly in the mixed solvent of tetrahydrofuran (THF) and water. Static light scattering was used to monitor the forming process of the micelles and to measure the critical water content. The diameter and the polydispersity of the micelles were affected by the initial concentration of ACAL in THF and the dropping speed of water was studied, and were measured by the dynamic light scattering. The scanning electron microscope (SEM) and the atomic force microscope (AFM) were also used to characterize the feature of the micelles. Results show that the acetylized modification is a good method for perparing lignin-based spherical micelles with regular structure, and the structure also has a good rigidity and stability in the drying condition. The diameter and the polydispersity of the micelles can be controlled by the solution initial concentration and the water added speed. According to the analaysis, the pi-pi interaction between the aromatic nucleus in ACAL is stronger than in AL, and the stronger pi-pi interaction is considered to play an important role in the formation of the micelles.