Synthesis and Characterization of Superabsorbent Hydrogels From Carboxymethyl Starch and Starch Blends by Gamma Irradiation

ABSTRACT Superabsorbent polymers (SAPs) are three‐dimensional polymer networks that can absorb and keep tens to hundreds of times their initial weight of distilled water. Using natural polymers with promising properties such as biocompatibility and biodegradability has received more attention for SAPs production. In this study, SAPs were synthesized from a blend of carboxymethyl starch (CMS) and starch by the gamma irradiation method as a cross‐linker. The effect of the preparation conditions such as total solute concentration, CMS to starch ratio, and gamma irradiation doses on hydrogel properties, was investigated. The gel fraction and swelling ratio of samples were in the range of 14%–75% and 7–80 g/g, depending on preparation conditions. Moreover, results showed that the gel fraction and swelling ratio of CMS/starch hydrogels with increasing concentration, starch ratio, and gamma irradiation doses increased and decreased, respectively. As diffusion coefficients for samples increased, swelling ratios increased as well. The water retention capacity of hydrogels at high temperatures and under centrifugal force offered the appropriate properties of hydrogels as SAPs. A Fourier transform infrared spectroscopy (FTIR) analysis proved crosslinking after gamma irradiation. The scanning electron microscope (SEM) illustrated a porous structure. This study effectively synthesized SAPs from a blend of CMS and starch using gamma irradiation. The preparation conditions significantly influenced the hydrogel properties, with higher concentrations and starch ratios increasing the gel fraction and swelling ratio, while higher gamma irradiation doses had the opposite effect. The hydrogels demonstrated excellent water retention capacity, making them suitable for SAP applications.