Dual Physical Crosslinking Strategy to Construct Moldable Hydrogels with Ultrahigh Strength and Toughness

Abstract

A dual physical crosslinking (DPC) strategy is used to construct moldable hydrogels with ultrahigh strength and toughness. First, polyelectrolyte complex (PEC) hydrogels are prepared through the in situ polymerization of acrylic acid monomers in the concentrated chitosan (Ch) solutions. Subsequently, Ag + ions are introduced into the PEC hydrogels to form coordination bonds between NH 2 and COOH groups. High-density electrostatic interaction and coordination bonds endow the DPC hydrogels with high strength and toughness. The mechanical properties of the DPC hydrogels strongly depend on the weight ratio of Ch to poly(acrylic acid) and the loading concentration of Ag + ions. When the loading concentration of Ag + ions is in the range of 1.0-1.5 mol L −1 , DPC 0.10-0.25 hydrogels display the maximum tensile strength (24.0 MPa) and toughness (84.7 MJ m −3 ) with a strain of more than 600%. Specially, the DPC hydrogels display an excellent moldable behavior due to the reversible properties of the electrostatic interaction and coordination bonds. The DPC strategy can also be applied in various other systems and opens a new avenue to fabricate hydrogels with outstanding mechanical properties and antibacterial activities.

Chemical unfolding of protein domains induces shape change in programmed protein hydrogels

“…Several approaches have been proposed to improve their stiffness and extensibility. One method is through using a double-network crosslinking strategy, either by secondary polymer network, using multivalent ions, or by nanoparticles [4][5][6][7][8][9][10] . Furthermore, polymer hydrogels are being used in shape-memory field.…”

In situ fabrication of CuO/UHMWPE nanocomposites and their tribological performance

“…When a low content of nano‐CuO is filled into UHMWPE resin, CuO nanoparticles are highly dispersed in the matrix and have a good interaction with the UHMWPE matrix. The rigid CuO with high elastic modulus might act as a physical crosslinking point in the matrix by the interaction between the nanofiller and the matrix . When the nanocomposite is subjected to an external force, the load would be transferred to CuO through the organic–inorganic interface, and the nano‐CuO particles would bear a part of the load, and the hardness, stiffness and strength of the nanocomposites will be improved .…”

High‐Strength and Tough Crystalline Polysaccharide‐Based Materials†

“…Traditional cellulose‐ or chitin‐based materials are formed through hydrogen bonding and hydrophobic interactions as well as chain entanglements, accompanied by a certain degree of crystallization. Various cross‐linking methods have been developed [ 36 ] and are mainly categorized into two kinds: chemical cross‐linking approaches ( i.e ., radical polymerization, [ 37 ] high energy irradiation, [ 38 ] and enzyme cross‐linking [ 39,40 ] ) and physical cross‐linking strategies (such as ionic interactions, [ 41,42 ] hydrogen bonding interactions [ 43 ] and protein interactions [ 44 ] ). However, all these cross‐linked cellulose‐ or chitin‐based materials are brittle, severely constraining their use in practical applications.…”

“…Physical interactions can also be used to construct high‐performance double cross‐linked hydrogels. Cao and co‐workers [ 41 ] proposed moldable chitosan/poly(acrylic acid) double cross‐linked hydrogels with ultrahigh mechanical strength and toughness of 24 MPa and 84.7 MJ m –3 , respectively (Figure 4). The electrostatic interactions and coordination bonds served as two physical cross‐linkers.…”