Uncovering the Polydisperse Characteristics of Modification Inhomogeneity for Starch during Oxidation by Sodium Periodate

Revealing the modification inhomogeneity at the molecular level is important to understand the structure–property relationship for polysaccharide derivatives. Herein, we report a study to uncover the polydisperse characteristics of inhomogeneity in both the chemical composition and molecular structure of dialdehyde starch (DA-starch) prepared by heterogeneous oxidation. Based on the difference in the ratio (r) of refractive and absorbance index increments or absorbance index increments at two different wavelengths for modified and intact units, we have developed a universal theoretical method to analyze the microscopic chemical composition of each fraction, which has been proved to show high accuracy (relative deviation within ±2%) by analyzing the experimental data using quadruple-detection size-exclusion chromatography. In particular, the result has demonstrated that the degree of modification is much lower for DA-starch chains with larger molecular sizes and higher molar masses. In addition, by analyzing the polydisperse characteristics of inhomogeneity in the molecular structure, we have revealed the slight change of size-mass scaling relation; to be specific, starch macromolecules are oxidized and degraded to less branched DA-starch fragments. We believe that the present study provides a fresh perspective regarding the modification inhomogeneity of polysaccharide derivatives, which is useful for practical industry applications.