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With the development of high-pressure apparatus, in situ characterization methods and theoretical calculations, high-pressure technology becomes a more and more important method to synthesize new compounds with unusual structures and properties. By compressing compounds containing unsaturated carbon atoms, novel poly-ionic polymers, graphanes and carbon nanothreads were obtained. Their compositions and structures were carefully studied by combining multiple cutting-edge technologies, like the in situ high-pressure X-ray and neutron diffraction, transmission electron microscopy, pair distribution function, solid-state nuclear magnetic resonance and gas chromatography-mass spectroscopy. The reaction mechanisms were investigated based on the crystal structure at the reaction threshold pressure (the pressure just before the reaction taking place), the long-range and short-range structure of the product, molecular structure of the intermediates, as well as the theoretical calculation. In this review, we will summarize the synthesis of carbon materials by compressing the unsaturated compounds and its reaction characteristics under extreme conditions. The topochemical reaction mechanism and related characterization methods of the molecular system will be highlighted. This review will provide a reference for designing chemical reaction and exploring novel carbon materials under high-pressure condition.

The interaction of water within synthetic and natural hydrogel systems is of fundamental importance in biomaterial science. A systematic study is presented on the swelling behavior and states of water for a polyethylene glycol-diacrylate (PEGDA)-based model neutral hydrogel system that goes beyond previous studies reported in the literature. Hydrogels with different network structures are crosslinked and swollen in different combinations of water and phosphate-buffered saline (PBS). Network variables, polyethylene glycol (PEG) molecular weight (MW), and weight fraction are positively correlated with swelling ratio, while “non-freezable bound water” content decreases with PEG MW. The presence of ions has the greatest influence on equilibrium water and “freezable” and “non-freezable” water, with all hydrogel formulations showing a decreased swelling ratio and increased bound water as ionic strength increases. Similarly, the number of “non-freezable bound water” molecules, calculated from DSC data, is greatest—up to six molecules per PEG repeat unit—for gels swollen in PBS. Fundamentally, the balance of osmotic pressure and non-covalent bonding is a major factor within the molecular structure of the hydrogel system. The proposed model explains the dynamic interaction of water within hydrogels in an osmotic environment. This study will point toward a better understanding of the molecular nature of the water interface in hydrogels.

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2,5-Furandicarboxylic acid (FDCA) is one of the top-12 value-added chemicals from sugar. Besides the wide application in chemical industry, here we found that solid FDCA polymerized to form an atomic-scale ordered sp3-carbon nanothread (CNTh) upon compression. With the help of perfectly aligned π–π stacked molecules and strong intermolecular hydrogen bonds, crystalline poly-FDCA CNTh with uniform syn-configuration was obtained above 11 GPa, with the crystal structure determined by Rietveld refinement of the X-ray diffraction (XRD). The in situ XRD and theoretical simulation results show that the FDCA experienced continuous [4 + 2] Diels–Alder reactions along the stacking direction at the threshold C···C distance of ∼2.8 Å. Benefiting from the abundant carbonyl groups, the poly-FDCA shows a high specific capacity of 375 mAh g–1 as an anode material of a lithium battery with excellent Coulombic efficiency and rate performance. This is the first time a three-dimensional crystalline CNTh is obtained, and we demonstrated it is the hydrogen bonds that lead to the formation of the crystalline material with a unique configuration. It also provides a new method to move biomass compounds toward advanced functional carbon materials.

Pressure-induced polymerization of aromatics is an effective method to construct extended carbon materials, including the diamond-like nanothread and graphitic structures, but the reaction pressure of phenyl is typically around 20 GPa and too high to be applied for large-scale preparation. Here by introducing ethynyl to phenyl, we obtained a sp2–sp3 carbon nanoribbon structure by compressing 1,3,5-triethynylbenzene (TEB), and the reaction pressure of phenyl was successfully decreased to 4 GPa, which is the lowest reaction pressure of aromatics at room temperature. Using experimental and theoretical methods, we figured out that the ethynylphenyl of TEB undergoes [4 + 2] dehydro-Diels–Alder (DDA) reaction with phenyl upon compression at an intermolecular C···C distance above 3.3 Å, which is much longer than those of benzene and acetylene. Our research suggested that the DDA reaction between ethynylphenyl and phenyl is a promising route to decrease the reaction pressure of aromatics, which allows the scalable high-pressure synthesis of nanoribbon materials.

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Stereolithography (SL) has several advantages over traditional biomanufacturing techniques such as fused deposition modeling, including increased speed, accuracy, and efficiency. While SL has been broadly used in tissue engineering for the fabrication of three-dimensional scaffolds that can mimic the in vivo environment for cell growth and tissue regeneration, lithographic printing is usually performed on single-component materials cured with ultraviolet light, severely limiting the versatility and cytocompatibility of such systems. In this Color images are available online. study, we report a highly tunable, low-cost photoinitiator system that we used to establish a systematic library of crosslinked materials based on low molecular weight poly(ethylene glycol) diacrylate. We assessed the physicochemical properties, photocrosslinking efficiency, cost performance, and biocompatibility to demonstrate the capability of manufacturing a multimaterial complex tissue scaffold. Stereolithography (SL) has advantages over traditional biomanufacturing techniques, including accuracy and efficiency. While SL has been broadly used for fabricating three-dimensional scaffolds that can mimic the in vivo environment for cell growth and tissue regeneration, lithographic printing is usually performed on single-component materials cured with ultraviolet light, severely limiting the versatility and cytocompatibility of such systems. In this study, we report a highly tunable photoinitiator system and establish a systematic library of crosslinked materials based on poly(ethylene glycol) diacrylate. We assessed the physicochemical properties, photocrosslinking efficiency and biocompatibility to demonstrate the capability of manufacturing a multimaterial complex tissue scaffold.