| Abstract: | As a source of starch, Pueraria thomsonii Benth. was selected to synthesize carboxymethyl starch (CMS) with monochloroacetic acid (MCA) in the presence of sodium hydroxide for the first time. The influence of the molar ratio of NaOH/AGU and MCA/AGU, reaction time, temperature, and water content of solvent on the degree of substitution and reaction efficiency were studied. IR spectrometry showed bands at 1609, 1420, and 1369 cm−1 due to –COO− symmetric and asymmetric stretching vibration when starch was successfully substituted. The SEM results displayed that the granules were agglomerate, and curly wrinkles appeared upon carboxymethylation. XRD revealed that the crystallinity reduced from 41.45 to 5.91%. Furthermore, the 13C NMR spectra of the CMS showed a broad band at d = 178.85 ppm, which was assigned to the –CO carbon (C‐8) of the carboxymethyl group. |
