A universal strategy for preparing tough and smart glassy hydrogels

Hydrogels with ultra-highly additive adjustable toughness under quasi-isochoric conditions

“…1d–f, the P(IBA- co -AAm) gels at 25 °C manifested a tremendously high Young's modulus and an obvious yielding point at low deformation, followed by large-scale plastic deformation, resembling the tensile behavior of typical glassy materials. 25,26 Upon heating, the gel demonstrated remarkable softening performance under uniaxial tensile measurement, with rigidity and fracture stress decreasing more than 3 and 2 decades, respectively, while the extensibility was significantly improved to 3200% at 60 °C. At the same time, the yielding point as well as the yielding plateau disappeared, featuring a rubbery material.…”

Ultra-stiff and tough hydrogels based on small but strong hydrophobic associations via a low-reactive hydrophilic monomer

“…[1][2][3][4] Many strong and tough hydrogels, such as double-network hydrogels, 5,6 nanocomposite hydrogels, 7,8 slide-ring hydrogels, 9,10 and conjoined-network hydrogels, 11,12 have been developed by incorporating energy dissipation mechanisms and tailoring the network structure. In recent years, great progress has been made in stiffening hydrogels, such as increasing polymer or cross-linking density, 13 enhancing association, 14 forming multiple networks, 15 and so on. But, there has only been limited development in simultaneously stiffen-ing and toughening hydrogels because stiffness and toughness are generally mutually exclusive.…”

A double-well potential model for glass transition in a glassy hydrogel undergoing bi-stable interactions with water

“…To improve the mechanical properties of hydrogels, doublenetworks, 3 slide-ring crosslinking 10,11 and physical entanglement 12 have been employed. There were many studies to investigate the effects of gels' condensed states on the mechanical behavior of hydrogels, [13][14][15][16][17] including hydrogen bonds, 13 hydrophobic semi-permeable membranes, 14,15 and p bonds. 16 These condensed states enable water molecules to transit from bound water into free water after interacting with the polymer macromolecules.…”

“…A mechanical modulus of 50 MPa has been reportedly achieved for a glassy hydrogel with a water content of 50% at room temperature. [13][14][15] On the other hand, many studies had also been presented on viscoelastic and dynamic models of the soft matters. [18][19][20][21][22] For example, double-well potential models have been widely used to model the mechanical and thermodynamic behaviors of proteins, 23 hydrogen bonds, 24 soft media, 25 damped structures, 26,27 nanoscale structures 28 and fibrous gels.…”

“…Finally, the effectiveness of the proposed double-well model is verified using both finite element analysis (FEA) and experimental results of glassy hydrogels reported in the literature. [13][14][15]…”