Design and optimization of superabsorbent hydrogels based on acrylic acid/2‐acrylamido‐2‐methylpropane sulfonic acid copolymers

Although acrylic acid‐based superabsorbent hydrogels (SAHs) are widely used in hygiene and personal care applications, the low degrees of true ionization in such SAHs under practical application places a limit on the degree of superabsorbency that can be achieved. Herein, the preparation and optimization of SAHs based on copolymers of acrylic acid (AA) with 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS), a strong acid comonomer that remains ionized at all relevant physiological pH values, is described. AA‐AMPS recipes optimized using a central composite design response surface method demonstrate significantly enhanced absorbance under load (AUL) values (>15–20% increase) and comparable centrifuge retention capacity (CRC) values compared to the corresponding AA‐only controls while maintaining strong mechanics even in the swollen state (as much as twice the modulus of the commercial AA‐based superabsorbent). The simplicity of this recipe, coupled with the reproducible achievement of the improved superabsorbency properties using a small adaptation of the commercial SAH synthesis protocol, makes AA‐AMPS superabsorbent hydrogels potential candidates for use in commercial hygiene products. Superabsorbent hydrogels based on copolymers of acrylic acid and 2‐methylpropane sulfonic acid (AA/AMPS) are optimized via a design of experiments approach to swell faster and to significantly higher water contents than conventional superabsorbents.