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.