Poly(acrylic acid)/gum arabic/ZnO semi-IPN hydrogels: synthesis, characterization and their optimizations by response surface methodology

Synthesis of novel semi-interpenetrating poly(acrylic acid) (PAA)/gum arabic (AG)/ZnO hydrogels by in situ free radical polymerization was optimized using response surface methodology (RSM). The reaction variables were the molar ratio of the cross-linking agent (X-1), the weight percentage of gum arabic (AG) (X-2) as the reaction medium, and the amount of ZnO (X-3), each of which was considered at five levels. The evaluated responses in RSM based on the central composite design (CCD) were the formation of samples (Y-1), swelling ratio (Y-2), conversion (Y-3), and percentage of networking (Y-4). Zinc oxide particles (ZnO) were prepared through a cost-effective and safe method based on the mixing of zinc acetate solution, ammonia solution, and sodium hydroxide into a microwave oven. The synthesized ZnO particles and prepared semi-interpenetrating polymer network (semi-IPNs) were evaluated by energy dispersive X-ray analyzer (EDX) and scanning electron microscopy (SEM), respectively. Synthesized samples based on RSM showed that hydrogels with less than 0.75 g of gum do not have suitable desirability. Also, the confirmation of the appropriate amount of cross-linking agent in hydrogels is between 10 and 16 (mol %), and more than this amount, the desirability of the responses decreases sharply. The results showed that increasing the amount of GA, as a biological macromolecule, significantly improves hydrogel formation, swelling rate, conversion, and networking of semi-IPNs which for the sample proposed by RSM were 1, 245%, 86%, and 94.5%, respectively. [GRAPHICS] .