Effect of triple modification on structure and properties of sesbania gum

Sesbania gum (SG), as a natural polymer, was modified by combining acidolysis, hydroxypropylation and esterification of chlorosulfonic acid to well adjust its properties. The acidolysis and esterification lowered the swelling capacity of SG; while, the hydroxypropylation increased the swelling capacity of SG. The peak intensity of CH₂ groups was evidently influenced by the esterification, but was hardly affected by the acidolysis and hydroxypropylation. SG was a strip-shaped semi-crystalline polymer. The acidolysis and esterification were mainly accomplished on large particles. The effect of acidolysis and esterification on the key thermodynamic parameters was contrary to that of hydroxypropylation. The hydroxypropylation decreased the thermal stability of SG; while, the acidolysis and esterification raised its thermal stability. The onset decomposition temperature and melting enthalpy were distinctly reduced by the esterification. The removal rate of Zn²⁺ by sulfonated hydroxypropyl acidolysis sesbania gum (SHASG) could reach 75.5%.