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1. Quadruple Hydrogen Bond-Containing A-AB-A Triblock Copolymers: Probing the Influence of Hydrogen Bonding in the Central Block

   https://doi.org/10.3390/molecules26154705  

   Liu, Boer; Chen, Xi; Spiering, Glenn A.; Moore, Robert B.; Long, Timothy E. (August 2021, Molecules)

   This work reveals the influence of pendant hydrogen bonding strength and distribution on self-assembly and the resulting thermomechanical properties of A-AB-A triblock copolymers. Reversible addition-fragmentation chain transfer polymerization afforded a library of A-AB-A acrylic triblock copolymers, wherein the A unit contained cytosine acrylate (CyA) or post-functionalized ureido cytosine acrylate (UCyA) and the B unit consisted of n-butyl acrylate (nBA). Differential scanning calorimetry revealed two glass transition temperatures, suggesting microphase-separation in the A-AB-A triblock copolymers. Thermomechanical and morphological analysis revealed the effects of hydrogen bonding distribution and strength on the self-assembly and microphase-separated morphology. Dynamic mechanical analysis showed multiple tan delta (δ) transitions that correlated to chain relaxation and hydrogen bonding dissociation, further confirming the microphase-separated structure. In addition, UCyA triblock copolymers possessed an extended modulus plateau versus temperature compared to the CyA analogs due to the stronger association of quadruple hydrogen bonding. CyA triblock copolymers exhibited a cylindrical microphase-separated morphology according to small-angle X-ray scattering. In contrast, UCyA triblock copolymers lacked long-range ordering due to hydrogen bonding induced phase mixing. The incorporation of UCyA into the soft central block resulted in improved tensile strength, extensibility, and toughness compared to the AB random copolymer and A-B-A triblock copolymer comparisons. This study provides insight into the structure-property relationships of A-AB-A supramolecular triblock copolymers that result from tunable association strengths. 

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2. Phases of the hydrogen isotopes under pressure: metallic hydrogen

   https://doi.org/10.1080/23746149.2021.1961607  

   Silvera, Isaac F.; Dias, Ranga (January 2021, Advances in Physics: X)

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3. A multi-model assessment of the Global Warming Potential of hydrogen

   https://doi.org/10.1038/s43247-023-00857-8  

   Sand, Maria; Skeie, Ragnhild Bieltvedt; Sandstad, Marit; Krishnan, Srinath; Myhre, Gunnar; Bryant, Hannah; Derwent, Richard; Hauglustaine, Didier; Paulot, Fabien; Prather, Michael; et al (December 2023, Communications Earth & Environment)

   Abstract With increasing global interest in molecular hydrogen to replace fossil fuels, more attention is being paid to potential leakages of hydrogen into the atmosphere and its environmental consequences. Hydrogen is not directly a greenhouse gas, but its chemical reactions change the abundances of the greenhouse gases methane, ozone, and stratospheric water vapor, as well as aerosols. Here, we use a model ensemble of five global atmospheric chemistry models to estimate the 100-year time-horizon Global Warming Potential (GWP100) of hydrogen. We estimate a hydrogen GWP100 of 11.6 ± 2.8 (one standard deviation). The uncertainty range covers soil uptake, photochemical production of hydrogen, the lifetimes of hydrogen and methane, and the hydroxyl radical feedback on methane and hydrogen. The hydrogen-induced changes are robust across the different models. It will be important to keep hydrogen leakages at a minimum to accomplish the benefits of switching to a hydrogen economy. 

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4. Controlling the Reactivity of a Metal-Hydroxo Adduct with a Hydrogen Bond

   https://doi.org/10.1021/jacs.1c06199  

   Opalade, Adedamola A.; Hessefort, Logan; Day, Victor W.; Jackson, Timothy A. (September 2021, Journal of the American Chemical Society)
5. Pushing the limits of the hydrogen bond enhanced halogen bond—the case of the C–H hydrogen bond

   https://doi.org/10.1039/d2sc03792k  

   Decato, Daniel A.; Sun, Jiyu; Boller, Madeleine R.; Berryman, Orion B. (September 2022, Chemical Science)

   C–H hydrogen bonds to iodine halogen bond donors are shown to improve halogen bonding and molecular preorganization. 

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