Ultrastretchable, Super Tough, and Rapidly Recoverable Nanocomposite Double‐Network Hydrogels by Dual Physically Hydrogen Bond and Vinyl‐Functionalized Silica Nanoparticles Macro‐Crosslinking

Abstract

It remains a challenge to develop tough hydrogels with recoverable or healable properties after damage. Herein, a new nanocomposite double‐network hydrogel (NC‐DN) consisting of first agar network and a homogeneous vinyl‐functionalized silica nanoparticles (VSNPs) macro‐crosslinked polyacrylamide (PAM) second network is reported. VSNPs are prepared via sol‐gel process using vinyltriethoxysilane as a silicon source. Then, Agar/PAM‐SiO2 NC‐DN hydrogels are fabricated by dual physically hydrogen bonds and VSNPs macro‐crosslinking. Under deformation, the reversible hydrogen bonds in agar network and PAM nanocomposite network successively break to dissipate energy and then recombine to recover the network, while VSNPs in the second network could effectively transfer stress to the network chains grafted on their surfaces and maintain the gel network. As a result, the optimal NC‐DN hydrogels exhibit ultrastretchable (fracture strain 7822%), super tough (fracture toughness 18.22 MJ m‐3, tensile strength 431 kPa), rapidly recoverable (≈92% toughness recovery after 5 min resting at room temperature), and self‐healable (can be stretched to 1331% after healing) properties. The newly designed Agar/PAM‐SiO2 NC‐DN hydrogels with tunable network structure and mechanical properties by multi‐bond crosslinking provide a new avenue to better understand the fundamental structure‐property relationship of DN hydrogels and broaden the current hydrogel research and applications.

Reversibly highly stretchable and self‐healable zwitterion‐containing polyelectrolyte hydrogel with high ionic conductivity for high‐performance flexible and cold‐resistant supercapacitor

“…The VSNPs were first prepared in an aqueous solution using a general sol–gel process. Based on the previous study, the concentration of VSNP in the hydrogel was fixed to 1 wt% relative to AM to obtain good mechanical properties of hydrogel . AM, SBMA, AMPS, VSNPs, and UV‐initiator were first added into water to form a homogeneous solution.…”

“…The highest toughness (2.7 MJ m −3 ) of P(AM‐SBMA‐AMPS)‐SiO 2 hydrogel is 2.4 times higher than that of PAM‐SiO 2 hydrogel (1.1 MJ m −3 ) (Figure 2i). The enhanced mechanical properties of P(AM‐SBMA‐AMPS)‐SiO 2 hydrogels is believed to stem from the dynamic electrostatic interactions by self‐associating of SBMA and between the cationic groups of SBMA and negatively charged AMPS and hydrogen bonding among PAM chains in the zwitterion‐containing polyelectrolyte hydrogels, acting as reversible sacrificial bonds to dissipate energy, and VSNPs multifunctional crosslinkers in the nanocomposite network can effectively transfer stress to the network chains grafted on their surfaces and maintain the gel network, which makes the gels ultratough and stretchable …”

“…Moreover, considering that chemical crosslinking not only largely constrains the mobility of polymer chains and hinders the self‐healing abilities of hydrogels but also causes inhomogeneous network, which is unfavorable for ion transportation in hydrogel GPEs . Vinyl‐functionalized silica nanoparticles (VSNPs) were chosen to function as multifunctional crosslinkers and stress transfer centers . In this way, benefiting from the combined advantage of VSNP crosslinked homogeneous network structure and the polymerizable zwitterionic ion transport enhancers, such kind of zwitterion‐containing polyelectrolyte hydrogels without doping electrolyte can serve as ion conducting GPE with simultaneously enhanced stretchable, self‐healable, cold‐resistant and ionic conductive merits for flexible SCs.…”

Multi-Sacrificial Bonds Enhanced Double Network Hydrogel with High Toughness, Resilience, Damping, and Notch-Insensitivity

“…Figure 1 presents the preparation process and interactions of the CDN-gel. The alkoxy groups are first hydrolyzed into silanol groups in the presence of water, and the silanol groups then condensate to form a siloxane bond [ 24 , 25 ]. The free-radical grafting polymerization mechanism of the PVA/PAA hydrogel triggered by visible light with a CQ initiator was proposed in our previous work [ 20 ].…”

“…In this work, monomer AA not only grafted with VSTO, leading to the formation of nanobrush gelators, but was also polymerized on the PVA backbone, resulting in a polymer network with a grafted structure. Simultaneously, the silanol can be adsorbed to the PVA on its OH-rich chains through hydrogen bonding, further leading to siloxane bridges [ 25 ]. Finally, the visible light-induced hydrogels were exposed to a saturation lithium solution to increase the crosslinking sites between the polymer chains by metal doping.…”