Stretching-induced ion complexation in physical polyampholyte hydrogels

Abstract

Recently, we have developed a series of charge balanced polyampholytes (PA) physical hydrogels by random copolymerization in water, which show extraordinarily high toughness, self-healing ability and viscoelasticity. The excellent performance of PA hydrogels is ascribed to the dynamic ionic bonds formation through inter-and intra-chain interactions. The randomness makes ionic bonds of a wide strength distribution, the strong bonds, serve as permanent crosslinking, imparting the elasticity, while the weak bonds reversibly break and re-form, dissipating energy. In this work, we developed a simple physical method, named as pre-stretch method, to promote the performance of PA hydrogels.By imposing a pre-stretch on the sample at as-prepared state, the ion complexation during dialysis is prominently accelerated and the final performance is largely promoted. Further analysis suggests that the strong bonds formation induced by pre-stretch is responsible for the change in final performance. Pre-stretch decreases the entropy of system and increases the chain alignment, resulting in an increased possibility for strong bonds formation.

Dual‐Crosslink Physical Hydrogels with High Toughness Based on Synergistic Hydrogen Bonding and Hydrophobic Interactions

“…In all the gels, E increased with f U or f S , due to the increase in crosslinking density. However, to achieve high toughness (usually indicated by extension work, W e , which is the area under the tensile stress–strain curve) needs balanced f U and f S . W e of the gels was in the range of 0.6–8.1 MJ m −3 , with the maximum value in the US‐6‐4 gel (Table ).…”

Mussel‐Inspired Contact‐Active Antibacterial Hydrogel with High Cell Affinity, Toughness, and Recoverability

“…Our AMD‐QCS polyampholyte hydrogels also displayed good recoverability and toughness because of the copolymerized MADA in the backbone. Of note, previously reported polyampholyte hydrogels were generally stiff, but lacked recoverability,[9a,29] because they were mainly composed of positively and negatively charged monomers. Therefore, there were strong electrostatic interactions between the charge groups, thereby restricting movement of the chain.…”

Bulk Energy Dissipation Mechanism for the Fracture of Tough and Self-Healing Hydrogels

“…As a model system, we use a polyampholyte (PA) physical hydrogel, which is strongly viscoelastic and exhibits excellent mechanical properties, such as high strength and extensibility, high fracture energy, self-resilience, and self-healing. 10,13, [29][30][31][32][33] The PA gel is synthesized from the radical copolymerization of cationic monomers and anionic monomers at a very high concentration with balanced charges. The polyampholytes thus obtained are topologically entangled and each polymer chain possesses oppositely charged ionic groups randomly distributed along the chain backbone.…”