Sodium tungstate as green cross‐linker to improve water absorbency of superabsorbent polymer

Abstract Superabsorbent polymers (SAPs) are attracting more research interests in many fields mainly due to its distinguished water‐absorbing performance. Among all the factors that severely affecting water absorption of SAPs, cross‐linkers play a non‐negligible role in shaping the stable cross‐linked networks of SAPs. As for cross‐linking agents, previous studies have focused on the chemical cross‐linker as well as functional nanoparticle cross‐linker. Though their corresponding SAPs can achieve high water uptake capacity, the sustainable development of such SAPs was still limited by the natural defects of these cross‐linkers. Herein, we reported small‐molecule sodium tungstate (STD) as one novel cross‐linker to optimize water‐holding capabilities of SAPs. STD shows a high affinity to polymeric chains mainly via multiple hydrogen bonding interactions. The resultant poly(acrylic acid)/STD SAP exhibited a satisfactory water‐absorbing capacities with swelling ratios of 7527 g/g in distilled water, 95 g/g in 0.9 wt% NaCl solution and 2210 g/g in 3 wt% urea solution, respectively. In addition, such high water absorbency was achieved within SAP system just made up of a sole polymer and a sole cross‐linker, implying that STD can be used as novel cross‐linker to promote the green development of SAPs.