Mechanical properties articles within Nature Chemistry

Featured

  • Article |

    Light-induced azobenzene cis/trans isomerization has been extensively investigated, but the mechanical strength of its cis/trans structure is not well understood. Now it has been shown that cis azobenzene is mechanically less stable than the trans isomer due to its regiochemical structure, as revealed by single-molecule force spectroscopy.

    • Yiran Li
    • , Bin Xue
    •  & Yi Cao

  • News & Views |

    Scientists have been studying how polymers break in solutions for decades, but the mechanism by which chains are stretched to the point of covalent bond scission is not trivial. Now, an experiment series provides ample support for a dynamic model in which chains uncoil from end to middle, while concurrently relaxing.

    • Charles E. Diesendruck

  • In Your Element |

    Fiona C. Meldrum and Helmut Cölfen chalk up some of the myriad forms and uses of calcium carbonate to burnish a ‘dull’ reputation.

    • Fiona C. Meldrum
    •  & Helmut Cölfen

  • Article |

    Extensive crosslinking in thermosetting polymers provides their desirable durability but makes them difficult to recycle. Now acetal-based monomers containing nucleophilic pendant groups have been incorporated into polyurethanes, which are stable in aqueous acid yet degradable at room temperature under organic acidic conditions. The degradation products were upcycled into higher-value, long-lasting materials.

    • Ephraim G. Morado
    • , Mara L. Paterson
    •  & Steven C. Zimmerman

  • News & Views |

    Mechanical force has recently become a new tool for chemists to create colours, trigger reactions, and develop advanced fabrication techniques not possible using other methods. Force-induced multiple colouring has now been developed as a printing technique in soft lithography, enabling the colouring of polymeric materials without inks.

    • Xiaocun Lu

  • News & Views |

    Innovations in instrumentation together with new strategies of data collection and processing have been shown to solve the problem of data quality for time-resolved in situ X-ray diffraction studies on ball milling, opening new horizons in mechanochemistry.

    • Elena Boldyreva

  • Article |

    Iron-catalysed [2+2] cycloaddition/oligomerization of neat butadiene affords (1,n′-divinyl)oligocyclobutane—a telechelic, crystalline material consisting of 1,3-enchained cyclobutyl units. This oligocyclobutane can be chemically recycled to pure butadiene using the same iron catalyst employed in its synthesis, demonstrating design principles for next-generation plastic materials that can be returned to pristine monomer.

    • Megan Mohadjer Beromi
    • , C. Rose Kennedy
    •  & Paul J. Chirik

  • Article |

    Chemical reactions usually proceed through either a radical, concerted or ionic mechanism; transformations in which all three mechanisms occur are rare. Now, the mechanical dissociation of an N-heterocyclic carbene precursor has been shown to proceed with the rupture of a C–C bond through concomitant heterolytic, concerted and homolytic pathways.

    • Robert Nixon
    •  & Guillaume De Bo

  • Review Article |

    Cyclic polymers have a ring-like architecture and one of the most important consequences of this topology is the absence of any chain ends, which typically have a substantial impact on the physical properties of macromolecules. This Review Article discusses advances in the synthesis, purification and characterization of cyclic polymers and the potential applications they may prove useful for.

    • Farihah M. Haque
    •  & Scott M. Grayson

  • Article |

    Membranes with high selectivity and high permeance that allows rapid passage of solvent molecules are desirable for efficient separation processes. Microporous conjugated-polymer membranes have now been fabricated through surface-initiated polymerization. These membranes are capable of ultrafast organic-solvent nanofiltration because of the high porosity and pore interconnectivity originating from the rigid skeleton.

    • Bin Liang
    • , Hui Wang
    •  & Zhiyong Tang

  • News & Views |

    Molecular crystals have recently started to shake their inflexible reputation. Now, copper(II) acetylacetonate needles have been shown to be very flexible, and their mechanical deformation has been assessed through materials constants using methods customarily reserved for non-molecular materials.

    • Bart Kahr
    •  & Michael D. Ward

  • Article |

    Crystals are typically thought to be brittle and fragile materials, but needles of copper(II) acetylacetonate have now been shown to be flexible enough to be reversibly tied into a knot. Mechanistic investigations using synchrotron X-ray diffraction determined that the elastic bending occurs through rotation of the molecules within the crystal lattice.

    • Anna Worthy
    • , Arnaud Grosjean
    •  & John C. McMurtrie

  • News & Views |

    Gluing materials together underwater is a mighty challenge faced — and overcome — by mussels. It requires good adhesion and cohesion. Molecular-level mechanical measurements have now shown that cation–π interactions provide surprisingly strong cohesive abilities.

    • Henrik Birkedal

  • Article |

    Mechanochemically controlled polymerization is rare in polymer chemistry. Now, it has been shown that mechanical force can initiate and control the polymerization of an acrylate monomer. Piezochemical reduction of a copper(II) precursor using mechanical agitation of piezoelectric nanoparticles generates the polymerization activator required for controlled radical polymerization.

    • Hemakesh Mohapatra
    • , Maya Kleiman
    •  & Aaron Palmer Esser-Kahn

  • Review Article |

    Numerous dynamic molecular crystals whose physical properties can be switched by external stimuli have recently been developed. This Review discusses how the precise control of the electron, proton and molecular movement within the crystals through the application of external stimuli can lead to considerable changes in their properties.

    • Osamu Sato

  • Article |

    Polymers that are both elastic and self-healing are desirable for a variety of applications, but often rely on hydrogen bonding which makes them moisture-sensitive. Now, by incorporating metal–ligand interactions with different bond strengths into flexible polymer backbones, an elastomer has been devised that combines high stretchability and high dielectric strength with autonomous self-healing and mechanical actuation capabilities.

    • Cheng-Hui Li
    • , Chao Wang
    •  & Zhenan Bao

  • Article |

    Highly compressible crystalline materials typically rely on the high compressibility of their chemical bonds. Now, a family of LnFe(CN)6 frameworks (Ln = Ho, Lu or Y) has been shown to exhibit pronounced volumetric and linear compressibilities through a spring-and-gear mechanism instead, in which a torsionally flexible LnN6 unit twists reversibly under pressure.

    • Samuel G. Duyker
    • , Vanessa K. Peterson
    •  & Cameron J. Kepert

  • Article |

    Crystals of hexachlorobenzene easily break when pressed on the (100) face, but bend to 360° without disintegrating when stress is applied on the (001) face. In the latter case this extraordinary malleability arises from the segregation and sliding of layers of molecules in the crystal, a process in which halogen–halogen interactions are broken and reformed.

    • Manas K. Panda
    • , Soumyajit Ghosh
    •  & Panče Naumov

  • Article |

    Transferring molecular motion to macroscopic shape change of a crystal has potential application in actuators, or ‘artificial muscles’. Now, a single crystal of a Ni complex has been shown to exhibit a large, abrupt, temperature-induced crystal expansion/contraction near room temperature. The crystal deformation is induced by a collective 90° rotation of oxalate anions in the complex.

    • Zi-Shuo Yao
    • , Masaki Mito
    •  & Osamu Sato

  • News & Views |

    Force-induced covalent bond changes in mechanophore-linked polymers typically require large, irreversible material deformation, limiting successive activation cycles. Now, repeated force-induced reactions have been achieved by incorporating flex-activated mechanophores into elastomeric networks.

    • Nancy R. Sottos

  • Article |

    Radical polymerization of a metastable lactone intermediate — formed from carbon dioxide and butadiene using a palladium catalyst — produces a high-CO2-content (29 wt%) polymer. This approach circumvents the thermodynamic and kinetic barriers typically associated with direct copolymerization of carbon dioxide and olefins, and can also be applied to one-pot co- and terpolymerization of carbon dioxide and 1,3-butadienes.

    • Ryo Nakano
    • , Shingo Ito
    •  & Kyoko Nozaki

  • Article |

    Materials typically break down in response to the repeated mechanical forces that they experience during use. Now, it has been shown that a mechanochemically active polymer can respond to shear forces by forming more bonds than are broken, leading to improved mechanical properties under conditions that would otherwise be destructive.

    • Ashley L. Black Ramirez
    • , Zachary S. Kean
    •  & Stephen L. Craig

  • News & Views |

    Previous approaches to the development of self-repairing polymeric materials have required either the input of external energy or the use of a healing agent. Now, a new type of elastomer, in which hard/soft phase-separation occurs at the nanoscale, displays efficient and entirely autonomic self-repair through reversible hydrogen bonding.

    • Howard M. Colquhoun

  • Article |

    Polymer materials that could spontaneously heal like tissues in living systems would significantly improve the safety, lifetime, energy efficiency and environmental impact of man-made materials. Now, a general multiphase design of autonomous self-healing elastomeric materials that do not require the input of external energy or healing agents is reported.

    • Yulin Chen
    • , Aaron M. Kushner
    •  & Zhibin Guan

  • Research Highlights |

    The complex pore structures of mesoporous crystals can be elucidated by assessing the curvature of their boundary surface.

    • Neil Withers

  • In Your Element |

    Jean-Marie Tarascon ponders on the value of lithium, an element known for about 200 years, whose importance is now fast increasing in view of the promises it holds for energy storage and electric cars.

    • Jean-Marie Tarascon

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