Constructive adaptation of 3D-printable polymers in response to typically destructive aquatic environments

Abstract

In response to environmental stressors, biological systems exhibit extraordinary adaptive capacity by turning destructive environmental stressors into constructive factors; however, the traditional engineering materials weaken and fail. Take the response of polymers to an aquatic environment as an example: water molecules typically compromise the mechanical properties of the polymer network in the bulk and on the interface through swelling and lubrication, respectively. Here, we report a class of 3D-printable synthetic polymers that constructively strengthen their bulk and interfacial mechanical properties in response to the aquatic environment. The mechanism relies on a water-assisted additional cross-linking reaction in the polymer matrix and on the interface. As such, the typically destructive water can constructively enhance the polymer's bulk mechanical properties such as stiffness, tensile strength, and fracture toughness by factors of 746–790%, and the interfacial bonding by a factor of 1000%. We show that the invented polymers can be used for soft robotics that self-strengthen matrix and self-heal cracks after training in water and water-healable packaging materials for flexible electronics. This work opens the door for the design of synthetic materials to imitate the constructive adaptation of biological systems in response to environmental stressors, for applications such as artificial muscles, soft robotics, and flexible electronics.

Bone-inspired stress-gaining elastomer enabled by dynamic molecular locking

“…The cross-linking reaction of the pre-reserved reactive groups was used to enhance the storage modulus; however, it embrittled the polymer. Yu et al ( 16 ) used a water-assisted cross-linking reaction mechanism to prepare a self-strengthening polymer, which, however, required aquatic environment. In addition, both SLE and modulus changes after stress loading for all the developed polymers were limited.…”

“…( A ) Schematics of the stress-gaining process of native bone (a) and covalently cross-linked polymers via dynamic molecular locking (b). ( B ) Strength and modulus changes after stress loading of traditional, state-of-the-art self-strengthening polymers and our polymer [( 9 ): traditional materials; ( 15 ): slide-ring hydrogels; ( 12 ): polydomain nematic liquid crystal elastomers; ( 10 ): freeze-thawed polyvinyl alcohol hydrogel; ( 14 ): segmented polyurethane elastomers; ( 11 ): poly(ethylene-propylene-diene monomer) elastomer; ( 13 ): double-network hydrogels; ( 16 ): water-strengthening polyurethane].…”

Self‐Assembled Robust 2D Networks from Magneto‐Elastic Bars

“…Reversible crosslinks and selfhealing have been extensively studied in polymeric materials but not in the context of magneto-elastic materials. [32][33][34][35] By noticing that embedding magnets in a pre-constructed elastic network cannot endow the system with the self-healing feature, we adopt a self-assembly approach to build such a magneto-elastic network from randomly distributed unit elements. Specifically, magnets and magnetic particles are ideal "sticky ends" for self-assembly and self-healing.…”