Modified Lignin with Anionic Surfactant and Its Application in Controlled Release of Avermectin

Alkali lignin (AL), an anionic polymer, is a byproduct of the paper industry. AL was first modified by quaternization to synthesize quaternized alkali lignin (QAL). The aim of the present study is to reveal the effects of sodium dodecyl benzenesulfonate (SDBS) on the microstructure of QAL. The interaction between SDBS and QAL is studied by means of zeta potential, fluorescence spectrophotometer, and static contact angle measurement. The results indicated that there is an electrostatic interaction and a hydrophobic interaction between QAL and SDBS. The SDBS/QAL complex can self-assemble into lignin-based colloidal spheres (LCSs) in an ethanol/water mixture, which have remarkable avermectin (AVM) encapsulation efficiency and antiphotolysis performance. The cumulative release amount of AVM encapsulated by LCS (LCS@AVM) after 72 h was 77%, and the release was still going on. The release behaviors of LCS@AVM can be controlled by adjusting the ratio (w/w) of LCS to AVM. More than 85% of AVM could be preserved even after 96 h of UV irradiation. LCS showed controlled release and UV-blocking performance for AVM.