Fully Reversible pH-Triggered Network Formation of Amphoteric Polyelectrolyte Hydrogels

Hydrogels are prepared through free radical copolymerization of MAA and DMAEMA employing only non-covalent interactions. The formation of hydrogels is dependent on pH as well as copolymer composition as a consequence of balance of predominantly attractive and repulsive ionic interactions and hydrogen bonding. The hydrogels are stable between pH 3 and 8 and for MAA to DMAEMA ratios of 62:38 to 68:32. Elastic and loss moduli are characterized as a function of pH. Hydrogels can reform from swollen microgel particles and offer the opportunity of recyclability. In model experiments it is shown that the flow through porous media can be controlled by varying the pH, which offers new possibilities such as controlling the supply of growth factors in tissue engineering scaffolds or as degradable fluid loss control agents for enhanced oil recovery.