Application of ftir in the determination of acrylate content in poly(sodium acrylate-CO-acrylamide) superabsorbent hydrogels

Abstract

Hydrogels have been prepared by free-radical solution copolymerization of acrylamide and sodium acrylate (NaAc), with molar ratio ranging from 25/75 to 80/20, respectively, using methylene bisacrylamide as the crosslinking agent. A FTIR spectroscopy procedure to determine the acrylate/acrylamide ratio in these hydrogels was proposed based on absorbance at 1410 cm -1 (nCOO-) and 2940 cm -1 (nCH and nCH 2). A straight line with a good linear correlation coefficient (0.998) was obtained by plotting the acrylate content (Ac%) versus relative absorbance (A rel = A 1410/A 2940). Results were confirmed by the amount of sodium cation released in acid medium determined by atomic absorption spectrometry.