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

摘要

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.