Hybrid Polymer-Network Hydrogels with Tunable Mechanical Response

Abstract

Hybrid polymer-network gels built by both physical and covalent polymer crosslinking combine the advantages of both these crosslinking types: they exhibit high mechanical strength along with excellent fracture toughness and extensibility. If these materials are extensively deformed, their physical crosslinks can break such that strain energy is dissipated and irreversible fracturing is restricted to high strain only. This mechanism of energy dissipation is determined by the kinetics and thermodynamics of the physical crosslinking contribution. In this paper, we present a poly(ethylene glycol) (PEG) based material toolkit to control these contributions in a rational and custom fashion. We form well-defined covalent polymer-network gels with regularly distributed additional supramolecular mechanical fuse links, whose strength of connectivity can be tuned without affecting the primary polymer-network composition. This is possible because the supramolecular fuse links are based on terpyridine-metal complexation, such that the mere choice of the fuse-linking metal ion adjusts their kinetics and thermodynamics of complexation-decomplexation, which directly affects the mechanical properties of the hybrid gels. We use oscillatory shear rheology to demonstrate this rational control and enhancement of the mechanical properties of the hybrid gels. In addition, static light scattering reveals their highly regular and well-defined polymer-network structures. As a result of both, the present approach provides an easy and reliable concept for preparing hybrid polymer-network gels with rationally designed properties.

Calcium‐Modified Silk as a Biocompatible and Strong Adhesive for Epidermal Electronics

“…Furthermore, the metal chelation for random coil chains offers suitable cohesion (Figure c‐ii), which endows the viscoelastic property to the film. In addition, the metal chelation allows for large energy dissipation at the interface with proper flowability (Figure c‐iii) . Therefore, the high adhesion by large energy dissipation with the good contact at the interface and appropriate cohesion enhances the peel strength of the Ca‐modified silk .…”

Dynamic Model Metallo‐Supramolecular Dual‐Network Hydrogels with Independently Tunable Network Crosslinks

“…Then, the gap is opened, and the required amount of metal ion solution is added to the polymer solution. Finally, the upper plate is lowered again to reach the desired gap, and the measurement is started . The standard Anton Paar solvent trap system is used to prevent solvent evaporation, which includes a solvent reservoir and a sealed chamber around the sample.…”

“…To address this challenge, following the introduction of tetra‐PEG networks, we develop a model dually crosslinked hydrogel with a homogeneous network structure . We use the versatile complexation of different metal ions with terpyridine ligands as the physical linkage.…”

New Developments in Medical Applications of Hybrid Hydrogels Containing Natural Polymers

“…The physical cross-links are also formed by crystallization, [56] between amphiphilic block and graft copolymers [57], and protein interactions [58]. Physically crosslinked hydrogels show stimuli-responsiveness and self-healing properties, but their mechanical strength is low and they often exhibit plastic flow [59].…”