Investigation on itaconic acid based pH and salt-responsive biopolymeric hydrogels

Hydrogels are water entrapping polymer network with responding to external stimuli (pH, temperature, electric field, chemical environments, etc.) are often denoted to as “intelligent” hydrogels. In this work, an unique pH and salt-responsive polymeric hydrogel was synthesised based on itaconic acid (IA) via condensation followed by free radical polymerization with ethylene glycol with acrylic acid (AA) using ammonium persulfate (APS) as an initiator sequentially. The formation of the synthesized hydrogels was studied using FT-IR spectroscopy. Swelling equilibrium studies in the pH range of 4.0 to 10.0 revealed that the extent of swelling increased with increasing pH due to deprotonation occurred in the hydrogels network. SEM analysis supported the surface morphology and tuning behaviour of pH in different buffer solutions. In addition, salt sensitive behaviour was performed with various chloride salt solutions viz., NaCl, CaCl2, AlCl3. There has been a reciprocal relationship was monitored while increasing charge of ion from monovalent to trivalent, decrease in the swelling behaviour. This could be related to the complexing ability of the hydrogels encouraging the increase in the crosslinking density. Swelling in salt solutions is of chief implication in many practical applications like personal hygiene products and release systems in agriculture.