Superabsorbent Hydrogels From Rice Starches With Different Amylose Contents

Bio‐based superabsorbent hydrogels from rice starches are prepared and characterized. Three rice starches with different amylose contents are carboxymethylated to obtain carboxymethyl rice starches (CMRS) with similar degrees of substitution. The hydrogels are then prepared from CMRS using citric acid as a cross‐linker. The chemical structure of CMRS and the formation of ester linkages in the hydrogels are confirmed by Fourier transform infrared spectroscopy (FTIR). Scanning electron microscope (SEM) reveal that rice starch hydrogels had a three‐dimensional interconnected porous structure. Free swelling capacity and absorbency under load (AUL) of the hydrogels are investigated. The results suggest that regardless of amylose content, the three rice starches yield hydrogels with similar characteristics. Amylose content appears to have a certain effect on mechanical strength but not on the free swelling capacity of the hydrogels.