Making Highly Elastic and Tough Hydrogels from Doughs

Abstract

A hydrogel is often fabricated from preexisting polymer chains by covalently crosslinking them into a polymer network. The crosslinks make the hydrogel swell‐resistant but brittle. This conflict is resolved here by making a hydrogel from a dough. The dough is formed by mixing long polymer chains with a small amount of water and photoinitiator. The dough is then homogenized by kneading and annealing at elevated temperatures, during which the crowded polymer chains densely entangle. The polymer chains are then sparsely crosslinked into a polymer network under an ultraviolet lamp, and submerged in water to swell to equilibrium. The resulting hydrogel is both swell‐resistant and tough. The hydrogel also has near‐perfect elasticity, high strength, high fatigue resistance, and low friction. The method is demonstrated with two widely used polymers, poly(ethylene glycol) and cellulose. These hydrogels have never been made swell‐resistant, elastic, and tough before. The method is generally applicable to synthetic and natural polymers, and is compatible with industrial processing technologies, opening doors to the development of sustainable, high‐performance hydrogels.

Ultra-tough self-healing hydrogel via hierarchical energy associative dissipation

“…HEAD gels outperformed the majority of known natural polymers as well as synthetic hydrogels in their comprehensive mechanical performance (Fig. 5b) 3,6,13,14,16,18,[39][40][41][42][43] . For example, HEAD gels could reach a comparable toughness as spider silk, but was 40 times more flexible.…”

Siloxane Molecules: Nonlinear Elastic Behavior and Fracture Characteristics

“…Recent works on tough hydrogels hint at a more complicated picture, in which network characteristics such as entanglements have a crucial effect on fracture. 5,6 Multiple length scales form the basis of the classical fracture mechanics picture. In the ideally brittle limit, dissipation and material failure occur on the scale of the atomistic separation length.…”

“…The resultant fracture energy should thus reflect the elastic energy stored within the entire chain instead of pure single bond scission. Recent works on tough hydrogels hint at a more complicated picture, in which network characteristics such as entanglements have a crucial effect on fracture. , …”

Epidermis-Inspired Porous Polymer Films Grown in situ from Hydrogel Surfaces

“…In the past decades, research towards artificial skin has been intensively carried out to imitate the multilayer structure, mechanical properties (flexibility and softness), sensing properties (pressure and thermal) and selfhealing properties of skin for diverse applications. [10][11][12][13][14][15][16][17][18][19][20][21][22] Diverse materials including 2D materials, 11 elastomers 14,23 and hydrogels [24][25][26][27][28][29][30][31] have been widely used to fabricate mimics. However, research inspired by the permeative and function of the epidermis remains underexplored.…”