The synthesis and incorporation of a star-shaped bio-based modifier in the acrylic acid based superabsorbent: a strategy to enhance the absorbency under load

ABSTRACT The mechanical strength of superabsorbents is an important practical factor that can be characterized by measuring the absorbency of the superabsorbent under load. In the last decades, many efforts have been devoted to enhancing the mechanical strength of superabsorbents. Herein, as an attempt to increase the superabsorbent mechanical strength, two types of star-shaped bio-based modifiers were designed and synthesized via condensation reaction between acids and alcohols. The chemical structures of the bio-based modifiers were characterized via FT-IR and 1H NMR analysis. Glycerin, lactic acid, succinic acid, and itaconic acid used for the synthesis of the star-shaped modifier, which further used in different ratios in the bulk of the superabsorbent. Moreover, another modifier was synthesized from glycerin, lactic acid, and methacrylic anhydride, and successfully used as a surface modifier for superabsorbents in different ratios. The absorption analysis showed that the employment of the optimum amount of the bulk modifier (4.75 wt.%) increases the AUL almost 4 units, without significant impacts on the water and NaCl solution absorbencies. Also, the incorporation of the optimum amount of the surface modifier increases the AUL about 3 units. As a result, the AUL value of the acrylic acid- sodium acrylate superabsorbent enhanced ~7 units by the incorporation of these bio-based modifiers-from 17.3 for the pristine superabsorbent to 24.2. Graphical Abstract