Acrylic Acid/Methyl Methacrylate Hydrogels. I. Effect of Composition on Mechanical and Thermodynamic Properties

The mechanical and thermodynamic properties of poly(acrylic acid-co-methyl methacrylate) hydrogels with varying ratios of AA/MMA are reported. Swelling capacity increases but elasticity decreases as the content of AA in the hydrogels increases. Thermodynamic analysis indicates that swelling is an unfavorable Δ[Gbar]1 > 0) and endothermic Δ[Hbar]1 > 0) process. Both thermodynamic quantities increase with increasing hydrophobic nature of the hydrogel. The amount of freezing and non-freezing water in the hydrogels was determined by DSC. The ratio of non freezing to total water content increases with the increasing hydrophobic nature of the hydrogels.