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Direct air capture (DAC) technologies that extract carbon dioxide from the atmosphere via chemical processes have the potential to restore the atmospheric CO2 concentration to an optimal level. This study elucidates structure‐property relationships in DAC by crystallization of bis(iminoguanidine) (BIG) carbonate salts. Their crystal structures are analyzed by X‐ray and neutron diffraction to accurately measure key structural parameters including molecular conformations, hydrogen bonding, and π‐stacking. Experimental measurements of key properties, such as aqueous solubilities and regeneration energies and temperatures, are complemented by first‐principles calculations of lattice and hydration free energies, as well as free energies of reactions with CO2, and BIG regenerations. Minor structural modifications in the molecular structure of the BIGs are found to result in major changes in the crystal structures and the aqueous solubilities within the series, leading to enhanced DAC. [ABSTRACT FROM AUTHOR]

Electrodes comprised of organic polymeric materials containing stable radicals have become attractive for incorporation into organic radical batteries. Specifically, the radical polymer poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA) exhibits extremely rapid electron charge transport rates, comparable to traditional transition metal ions. However, the structural reorganization that the polymer undergoes during charging is not well understood. Using small angle neutron scattering, we have investigated the structural changes the PTMA polymer exhibits with variation of radical concentration or oxidation. The results indicate that as the radical concentration is increased, the polymer becomes more inflexible and begins to aggregate with neighboring polymer chains as the radicals on the polymer align with neighboring solvated chains. Additional studies monitor the conformational changes of the PTMA copolymers with oxidation to mimic the structural changes that the polymer undergoes during charging. These results show that polymers with low radical densities are more susceptible to reorientation with charging than a polymer that is fully saturated with radical moieties. This study therefore provides seminal fundamental information that identifies the relationship between radical density and molecular structure providing crucial insight that is needed to improve the performance of organic radical batteries. [ABSTRACT FROM AUTHOR]

The properties of the interfacial layer between the polymer matrix and nanoparticles largely determine the macroscopic properties of polymer nanocomposites (PNCs). Although the static thickness of the interfacial layer was found to increase with the molecular weight (MW), the influence of MW on segmental relaxation and the glass transition in this layer remains to be explored. In this Letter, we show an unexpected MW dependence of the interfacial properties in PNC with attractive polymer-nanoparticle interactions: the thickness of the interfacial layer with hindered segmental relaxation decreases as MW increases, in sharp contrast to theoretical predictions. Further analyses reveal a reduction in mass density of the interfacial layer with increasing MW, which can elucidate these unexpected dynamic effects. Our observations call for a significant revision of the current understandings of PNCs and suggest interesting ways to tailor their properties. [ABSTRACT FROM AUTHOR]