Amazing stuff!
"... A pair of proof-of-concept papers out today in Science demonstrates that the same principle could allow material scientists to create and 3D print new types of flexible yet strong protective fabrics and even artificial muscles. ...
They started by coaxing myriad copies of X-shaped molecules to settle into a crystal, so that they lined up in two interpenetrating sheets: In one direction the tips of each molecular X nearly touched those adjacent to it, like XXXXXXX. The same pattern repeated in a perpendicular direction, creating an interlocking fishnet. But these links were held together by weak hydrogen bonds, which meant the meshed material could easily come apart. So, Dichtel and his colleagues added a silicon-based compound that inserted itself at the tips of each pair of Xs, strengthening these attachment points with tougher, more durable covalent bonds and producing a polymer composed of interlocking rings, each of which serves as “mechanical” bond further strengthening the material. ...
They started by coaxing myriad copies of X-shaped molecules to settle into a crystal, so that they lined up in two interpenetrating sheets: In one direction the tips of each molecular X nearly touched those adjacent to it, like XXXXXXX. The same pattern repeated in a perpendicular direction, creating an interlocking fishnet. But these links were held together by weak hydrogen bonds, which meant the meshed material could easily come apart. So, Dichtel and his colleagues added a silicon-based compound that inserted itself at the tips of each pair of Xs, strengthening these attachment points with tougher, more durable covalent bonds and producing a polymer composed of interlocking rings, each of which serves as “mechanical” bond further strengthening the material. ...
When a team ... wove just 2.5% of this new material into Ultem—a material made of high-strength fibers in the same family as Kevlar, the resulting fabric’s stiffness increased by nearly 50%. It’s still early days, but “almost every property we have measured has been exceptional in some way,” ..."
From the editor's summary and abstract:
"Editor’s summary
Architected materials are engineered such that the structure of the base elements affects the mechanical properties. This engineering provides the ability to tune the materials’ response to stresses. Zhou et al. present a new family called polycatenated architected materials that link together wireframe elements into three-dimensional structures (see the Perspective by Tawfick and Arretche). The design strategy allows for tailored mechanical responses that are useful for developing stimuli-responsive or energy-absorbing systems, along with morphing architectures. —Brent Grocholski
Abstract
Architected materials derive their properties from the geometric arrangement of their internal structural elements. Their designs rely on continuous networks of members to control the global mechanical behavior of the bulk.
In this study, we introduce a class of materials that consist of discrete concatenated rings or cage particles interlocked in three-dimensional networks, forming polycatenated architected materials (PAMs). We propose a general design framework that translates arbitrary crystalline networks into particle concatenations and geometries. In response to small external loads, PAMs behave like non-Newtonian fluids, showing both shear-thinning and shear-thickening responses, which can be controlled by their catenation topologies. At larger strains, PAMs behave like lattices and foams, with a nonlinear stress-strain relation.
At microscale, we demonstrate that PAMs can change their shapes in response to applied electrostatic charges. The distinctive properties of PAMs pave the path for developing stimuli-responsive materials, energy-absorbing systems, and morphing architectures."
From the editor's summary and abstract:
"Editor’s summary
A mechanically interlocked two-dimensional polymer forms as a layered solid that can be exfoliated in common organic solvents. Bardot et al. found that a molecule with four extended aromatic groups crystallizes in a layered structure supported by hydrogen bonds between hydroxyl groups. Infiltration of dialkyldichlorosilane was used to form siloxane linkages that created macrocyclic mechanical interlocks at every repeat unit. The addition of 2.5% by weight of this material to poly(ether imide) fibers increased their tensile modulus by 45% and ultimate stress by 22%. ...
Abstract
Mechanical bonds arise between molecules that contain interlocked subunits, such as one macrocycle threaded through another. Within polymers, these linkages will confer distinctive mechanical properties and other emergent behaviors, but polymerizations that form mechanical bonds efficiently and use simple monomeric building blocks are rare.
In this work, we introduce a solid-state polymerization in which one monomer infiltrates crystals of another to form a macrocycle and mechanical bond at each repeat unit of a two-dimensional (2D) polymer. This mechanically interlocked 2D polymer is formed as a layered solid that is readily exfoliated in common organic solvents, enabling spectroscopic characterization and atomic-resolution imaging using advanced electron microscopy techniques. The 2D mechanically interlocked polymer is easily prepared on multigram scales, which, along with its solution processibility, enables the facile fabrication of composite fibers with Ultem that exhibit enhanced stiffness and strength."
3D polycatenated architected materials (no public access)
Mechanically interlocked two-dimensional polymers (no public access)
A novel polymer is made of sheets of interlocking rings, like interpenetrating fishnets.
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