Swelling Rate Analysis of Anionic Hydrogels in Distilled Water and Various Solutions with Various Ionic Strengths

Anionic acrylamide-based hydrogels were synthesised through a free radical copolymerisation of acrylamide and acrylic acid co-monomers. The effect of the amount of ionisable monomer change on the network and also the change in ionic strength of swelling environment on the diffusion mechanism, equilibrium swelling, and equilibrium swelling rate of the hydrogels were analysed. Solutions of sodium hydroxide, ammonium nitrate, and ammonium sulphate with concentrations of 0.1, 0.5, and 1 M were chosen as electrolyte solutions. Swelling experiments were carried out byusing common methods of gel weighing and comparing swollen gel weight versus the dried ones. It was observed that as the acrylic acid monomers increase in the 3-dimensional network of hydrogel, the amount of equilibrium swelling and the swelling rate increase. Increasing the ionic strength of the surrounding solution causes decrease in the equilibrium swelling and the swelling rate of ionized gels. In solutions with a high ionic strength (ammonium sulphate 0.1 M) the swelling behaviour of the hydrogel was almost similar to that of neutral hydrogel with a similar composition.

Keywords:

hydrogel , electrolyte solution , acrylamide , swelling rate , diffusion mechanism , acrylic acid