Toughening Double‐Network Hydrogels by Polyelectrolytes

Abstract

The Hoffmeister effect of inorganic salts is verified as a promising way to toughen hydrogels, however, the high concentration of inorganic salts may be accompanied by poor biocompatibility. In this work, it is found that polyelectrolytes can obviously elevate the mechanical performances of hydrogels through the Hoffmeister effect. The introduction of anionic poly(sodium acrylate) into poly(vinyl alcohol) (PVA) hydrogel induces the aggregation and crystallization of the PVA to boost the mechanical properties of the resulting double-network hydrogel: elevation of 73, 64, 28, 135, and 19 times in the tensile strength, compressive strength, Young's modulus, toughness, and fracture energy compared with poly(acrylic acid), respectively. It is noteworthy that the mechanical performances of the hydrogels can be flexibly tuned by the variation of polyelectrolyte concentration, ionization degree, relative hydrophobicity of the ionic component, and polyelectrolyte type in a wide range. This strategy is verified to work for other Hoffmeister-effect-sensitive polymers and polyelectrolytes. Also, the introduction of urea bonds into the polyelectrolyte can further improve the mechanical properties and antiswelling capability of hydrogels. As a biomedical patch, the advanced hydrogel can efficiently inhibit hernia formation and promote the regeneration of soft tissues in an abdominal wall defect model. IntroductionAs one of the most extensively studied soft and wet materials with adjustable physical and chemical properties, hydrogels have

3D shape morphing of stimuli-responsive composite hydrogels

“…Thus, physical crystallization is the most common way to realize the gelation of PVA. 100 At present, there are three methods that researchers use for generating outnumbered crystallization inside PVA hydrogels: cyclic freezing–thawing, 101–104 solvent exchange, 102,105,106 and salting-out. 105,106 For the cyclic freezing–thawing procedure, the low temperature not only weakens the movement of chains but increases the contact time for PVA chains, resulting in higher crystallinity.…”

Developing conductive hydrogels for biomedical applications

“…Adopting dopants, such as dopamine (DA), phytic acid (PA), tannic acid (TA) or polyelectrolytes, has been proven to be a useful method to solve these problems. [43][44][45] Zhang et al proposed a conductive hydrogel taking advantage of polydopamine@Ppy (PDA@Ppy) nanocomposite which was prepared by the copolymerization of DA and pyrrole. 46 The addition of PDA not only overcame the hydrophobicity of Ppy to avoid the aggregation phenomenon but also provided more reaction sites, further improving the cross-linked degree of the resultant conductive hydrogels.…”

Stable Flexible Electronic Devices under Harsh Conditions Enabled by Double-Network Hydrogels Containing Binary Cations

“…8,11 Given the composition of hydrogels, the on-demand regulation of mechanical properties of hydrogels is mainly achieved by controlling the structures of polymer chains, crosslinking points, and water contents. Most approaches have been developed to construct mechanically robust hydrogels by various network structure designs, such as double network (DN), 12,13 dually cross-linked network, 14 topological network, 15,16 nanocomposite network, 17 etc. From another aspect, rich pores filled with water provide transportation paths for various mobile ions.…”

“…Ionic hydrogels, which are composed of cross-linked polymer networks, with a large amount of water and ions, are increasingly explored in fabricating flexible electronic devices due to their combined soft nature and ion transportation ability. − Mechanical robustness is critical to maintain the stability and integrity of ionic hydrogels under long-term mechanical loading. , Given the composition of hydrogels, the on-demand regulation of mechanical properties of hydrogels is mainly achieved by controlling the structures of polymer chains, cross-linking points, and water contents. Most approaches have been developed to construct mechanically robust hydrogels by various network structure designs, such as double network (DN), , dually cross-linked network, topological network, , nanocomposite network, etc. From another aspect, rich pores filled with water provide transportation paths for various mobile ions.…”