Study on water-absorbing behaviors of superabsorbent polymer enhanced by 1,2,3,4-butane tetracarboxylic acid cross-linker

superabsorbent polymers (SAPs) are famous for their excellent water absorption capability. In this work, poly (acrylic acid)-based superabsorbent polymer was developed via free radical polymerization by innovatively using 1,2,3,4-butane tetracarboxylic acid (BTA) as one unique physical cross-linker. Water-soluble BTA molecules contain four carboxyl groups that can interact with poly(acrylic acid) (PAA) polymeric chains through hydrogen bonds. Such force made the products swell but not dissolve in water, determining that BTA took a great role of cross-links. The effects of initiator, catalyzer, neutralizer and cross-linking agent on water-absorbing capacities of as-obtained PAA/BTA-SAP products were explored. The results revealed that swelling ratios of such PAA/BTA-SAP in distilled water was 4480 g/g, in 0.9 wt% NaCl solution was 55 g/g and in 5 wt% urea solution was 1890 g/g. Swelling kinetics indicated that polymer chains of the product in distilled water underwent relaxation and stretching in the swelling stage. The excellent water uptake was attributed to the formation of a well-structured three-dimensional network for SAPs via multiple hydrogen bonds between PAA polymer and BTA molecule. Therefore, the present work provides a new horizon to explore BTA as one unique cross-linker to prepare SAPs with the enhanced water uptake.