Salt (chemistry)

Engineering

Polymer chemistry

Materials science

Biochemistry

Chemical engineering

Ionic strength

Swelling

Osmotic pressure

Polymer

Organic chemistry

Aqueous solution

Composite material

Ionic bonding

Chemistry

Polyelectrolyte

Soft Matter

Polyelectrolyte gels exhibit intrinsic salt-sensitive swelling behaviour, which causes size instability in ionic environments. Thus, polyelectrolyte gels that show salt-insensitive swelling have been anticipated for applications in ionic environments, such as medical materials used in vivo. We found that double-network (DN) gels consisting of both a polyelectrolyte network and a non-ionic network are resistant to salt-sensitive swelling. This resistance is attributed to their lower osmotic pressure originating from mobile ions relative to the osmotic pressure of mixing at swelling equilibrium. Our investigation indicated that the two contrasting network structures within the DN gels are vital for achieving these properties, where the structures include a highly prestretched and sparse polyelectrolyte network and a coiled and dense non-ionic network. The salt-insensitivity of the DN gels will lead to their unique applications in ionic environments.

Double-network gels as polyelectrolyte gels with salt-insensitive swelling properties