Superabsorbent Hydrogels That Are Robust and Highly Stretchable

Abstract

Polymer hydrogels synthesized by chemical crosslinking of acrylate or acrylamide monomers can absorb more than 100 times their weight in water. However, such gels are usually fragile and rupture when stretched to moderate strains (∼50%). Many strategies have been developed to create tougher gels, including double-networking, incorporation of nanoparticles as cross-linkers, etc., but these strategies typically retard the water absorbency of the gel. Here, we present a new approach that gives rise to superabsorbent hydrogels having superior mechanical properties. The key to our approach is the self-cross-linking ability of N,Ndimethylacrylamide (DMAA). That is, we conduct a free-radical polymerization of DMAA (along with an ionic comonomer such as sodium acrylate) but without any multifunctional monomers. A hydrogel still forms due to interchain covalent bonds between the growing linear polymer chains. Gels formed by this route can be stretched up to 1350% strain in the unswollen state. The same gels are also superabsorbent and can imbibe up to 3000 times their weight in water (which is believed to be a record). Even in the swollen state, these gels can be stretched up to strains ∼400% before rupture, which substantially exceeds that of conventional superabsorbent gels. The superior properties of DMAAbased gels are attributed to a more uniform distribution of cross-links within their networks.

Characterization and Properties of Hydrogels Made from Neutral Soluble Chitosans

“…In contrast to super-swelling gels [28,29], the swelling of ViscoGel is modest. The magnitude of the swelling/shrinking of ViscoGel in different buffers was ±20%, even after 91 h exposure to the buffers in the range of pH 4-8.…”

A skin-like stretchable colorimetric temperature sensor

“…5d, various transparent soft materials were compared in terms of their strength and elasticity [53]. Hydrogels constitute another type of transparent soft films [54][55][56]. However, different from the mechanically tough PDMS, the hydrogels are usually mechanically weak owing to their "wet" components (hygrophilic gel).…”

Flexible Hydrogel Capacitive Pressure Sensor for Underwater Applications

“…The self-crosslinking ability of DMAA was used for thin film hydrogel synthesis as described previously [8]. Briefly, 33 wt % DMAA was dissolved in deionized (DI) water and nitrogen (N2) gas was bubbled through this solution for 45 min to remove dissolved oxygen.…”

“…Dimethylacrylamide (DMAA) based hydrogels have been widely investigated for biomedical and pharmaceutical applications because of its hydrophilic and biocompatible nature with associative properties [7,8]. These hydrogels, when synthesized by self-crosslinking in the presence of free radical initiators, exhibit excellent toughness and extensibility while having high swelling.…”