The effect of the solvent employed in the synthesis of hydrogels of poly (acrylamide-co-methyl methacrylate) on their structure, properties and possible biomedical applications

Abstract Polyacrylamide and poly(acrylamide-co-methyl methacrylate) hydrogels were synthesized in three different solvents: water, aqueous dioxane 50 vol% and aqueous ethanol 80 vol%. The obtained hydrogels were characterized by swelling behavior, FTIR, SEM, optical microscopy (OM) and DSC. The hydrogels showed a significant dependence of their microstructure and other properties with the solvent used during the synthesis. Hydrogels synthesized in water showed a poor incorporation of methyl methacrylate (MMA) units as evidenced by FTIR, while those synthesized in aqueous ethanol 80 vol% exhibited a higher incorporation of MMA as compared to the hydrogels obtained in aqueous dioxane 50 vol%. Although the incorporation of MMA is higher for the hydrogels synthesized in aqueous ethanol 80 vol%, these hydrogels displayed the highest swelling values (e.g., 6500% for the polyacrylamide hydrogel). These values are approximately 7-times higher than the swelling of equivalent hydrogels synthesized in water (900%). DSC results are consistent with swelling behavior, since the difference in the content of free water was 70, 9 and 6 mg of free water/mg of xerogel for the hydrogels of acrylamide synthesized in aqueous ethanol 80 vol%, water and aqueous dioxane 50 vol%, respectively. OM and SEM results reveal highly porous microstructures characteristic of superabsorbent materials. Only hydrogels synthesized in aqueous dioxane 50 vol% were studied as potential carriers for ciprofloxacin. Results demonstrated that most of the drug load is released during the first 6 h.