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초록

A green and efficient strategy for enhancing the aqueous solubility of chitosan (Chi) was developed by coupling ultrasonication with extremely mild acetic acid (AcA, 0.2–1.0 %). A comprehensive set of characterization techniques, including dynamic light scattering, pH, zeta potential analysis, UV–visible spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and thermogravimetric analyses, was employed to elucidate the physicochemical changes induced by this treatment. Mild AcA primarily facilitated protonation and increased accessibility of amino groups, while ultrasonication generated cavitation forces that disrupted hydrogen bonding and partially relaxed crystalline domains. These combined effects produced Chi with reduced particle size, enhanced amorphous character, increased optical clarity, and improved colloidal stability. Systematic evaluation of AcA concentration and sonication duration revealed an optimal processing window in which structural relaxation and controlled fragmentation enhanced solubility, whereas excessive sonication resulted in over-fragmentation and lower recovery yields. This study provides mechanistic insight into how cavitation-driven disruption synergizes with mild protonation to produce water-dispersible Chi under environmentally benign conditions, offering a sustainable alternative to conventional high-acid or energy-intensive dissolution approaches.

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