A quasi-periodic two-nanophase structure within starch-based hydrogels containing acetylated starch: An insight of small angle X-ray scattering

The inclusion of acetylated starch (AS) tunes the nanoscale characteristics of starch-based hydrogels, thereby enhancing their performance in biological, pharmaceutical, and material fields. Hence, quantitively analyzing the nanostructures of such hydrogels is conducive to guiding further improvements in their mechanical and functional properties. Through a small angle X-ray scattering (SAXS) analysis, we substantiated a quasi-periodic two-nanophase arrangement in starch-based hydrogels, and accordingly developed a comprehensive model consisting of Debye-Bueche, Teubner-Strey, and Beaucage functions. The result manifested that the incorporation of AS reduced the quasi-period of two-nanophase structure and the radius of gyration (R_g) of supramolecular clusters, augmented the degree of large inhomogeneities, and inhibited the phase segregation. These changes were attributable to the weakened hydrogen bonds and lessened helical ordering, as revealed by the Fourier transform infrared (FTIR) and ¹³C nuclear magnetic resonance (NMR) evaluations. Further, the variations in their nanostructures led to an enhanced water migration and an increased leached amylose content. Especially for the hydrogel containing 10% AS, the quasi-period and correlation length fell by 4.6 nm and 0.8 nm, respectively, with the relaxation time for interstitial water being delayed by 45.9 ms. This study provides a methodological reference to analyze the nanoscale features of bio-based hydrogels.