Poly(acrylic acid) (PAA) is considered as a crosslinking polymer for PVA because it has multiple carboxylic acid groups in its repeating units that can react with the hydroxyl groups in PVA, as well as desirable characteristics such as good water solubility Poly(acrylic acid) (PAA) was selected as a crosslinking agent because each monomer unit has a functional carboxyl group that can react with PVA