Synthesis of high degree of substitution amphiphilic starch by oxalic acid decomposition of starch in aqueous

The potential toxicity of organic solvents and high price of modifiers such as acyl halides limit the synthesis and application of amphiphilic starch. Therefore, it is urgent to develop novel methods for synthesizing highly substituted amphiphilic starch using low-cost modifiers. Herein, we proposed a novel strategy for the synthesis of amphiphilic stearic alcohol starch ester with a high degree of substitution in aqueous via oxalic acid decomposition, carboxylated starch and esterification during drying. Characterization revealed that oxalic acid decomposition and carboxylation play key roles in the synthesis of amphiphilic starch by enhancing the reactivity and complexation ability of starch with the stearic alcohol. Benefiting from this, amphiphilic starch with a degree of substitution of 0.041 was synthesized by reacting carboxylated starch with stearic alcohol during the transition from the liquid to the solid state of the complex. Furthermore, the amphiphilic nature of the synthesized starch allows it to act as an emulsion stabilizer with at least 14 days of anti-delamination stability. Additionally, amphiphilic starch was also used as a waterproof coating and elastic reinforcement agent with enhancing Young's modulus. Our findings contribute to the synthesis of amphiphilic starch and expand its applications due to its high degree of substitution.