Manufacturing of Starch Nanocrystals Graft Polycaprolactone Catalyzed by Natural Clay: Synthesis, Characterizations, and Thermal and Antioxidant Properties

This study presents an innovative approach for the production of starch nanocrystals (SNCs) grafted with polycaprolactone (PCL). Corn starch was subjected to hydrolysis using sulfuric acid (H2SO4), resulting in the formation of SNCs. These SNCs were subsequently grafted with polycaprolactone using Maghnite-H+ (an Algerian modified montmorillonite clay) as a solid acid catalyst. The resulting nanomaterial, denoted as SNCs-g-PCL, exhibited improved hydrophobic properties. Fourier-transform infrared spectroscopy (FTIR) revealed the presence of a distinctive carbonyl C = O band at 1726 cm−1 in the SNCs-g-PCL, indicating successful grafting. Nuclear Magnetic Resonance of protons (1H-NMR) exhibited new signals from the protons of PCL in the SNCs-g-PCL. Dynamic light scattering (DLS) measurements demonstrated an increase in the diameter of the starch nanocrystals after PCL grafting. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis revealed a reduction in crystallinity and a transition from well-defined SNCs nanocrystals to a disordered structure upon PCL grafting. Furthermore, the antioxidant properties of the SNCs, both before and after grafting, were evaluated using 1,1-diphenyl-2-phenyl hydrazine radical scavenging assays and ferric reducing antioxidant power assays. Nonetheless, the observed antioxidant activity was found to be comparable to that of ascorbic acid (vitamin C) with an EC50 (Half maximal effective concentration) of around 100 mg/ml. This study highlights the potential of SNCs-g-PCL nanocrystals as a promising nanomaterial with antioxidant properties, making them suitable for various applications in the fields of materials science.