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11. Dialing in Direct Air Capture of CO2 by Crystal Engineering of Bisiminoguanidines.

Author

Custelcean, Radu, Williams, Neil J., Wang, Xiaoping, Garrabrant, Kathleen A., Martin, Halie J., Kidder, Michelle K., Ivanov, Alexander S., and Bryantsev, Vyacheslav S.

Subjects
MOLECULAR structure, X-ray diffraction, MOLECULAR conformation, CHEMICAL processes, ATMOSPHERIC carbon dioxide, CARBON dioxide, CRYSTAL structure
Abstract

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]

Published
2020
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14. Interfacial Properties of Polymer Nanocomposites: Role of Chain Rigidity and Dynamic Heterogeneity Length Scale

Author

Cheng, Shiwang, primary, Carroll, Bobby, additional, Lu, Wei, additional, Fan, Fei, additional, Carrillo, Jan-Michael Y., additional, Martin, Halie, additional, Holt, Adam P., additional, Kang, Nam-Goo, additional, Bocharova, Vera, additional, Mays, Jimmy W., additional, Sumpter, Bobby G., additional, Dadmun, Mark, additional, and Sokolov, Alexei P., additional

Published
2017
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19. Controlling Interfacial Dynamics: Covalent Bonding versus Physical Adsorption in Polymer Nanocomposites

Author

Holt, Adam P., primary, Bocharova, Vera, additional, Cheng, Shiwang, additional, Kisliuk, Alexander M., additional, White, B. Tyler, additional, Saito, Tomonori, additional, Uhrig, David, additional, Mahalik, J. P., additional, Kumar, Rajeev, additional, Imel, Adam E., additional, Etampawala, Thusitha, additional, Martin, Halie, additional, Sikes, Nicole, additional, Sumpter, Bobby G., additional, Dadmun, Mark D., additional, and Sokolov, Alexei P., additional

Published
2016
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20. Unraveling the Mechanism of Nanoscale Mechanical Reinforcement in Glassy Polymer Nanocomposites

Author

Cheng, Shiwang, primary, Bocharova, Vera, additional, Belianinov, Alex, additional, Xiong, Shaomin, additional, Kisliuk, Alexander, additional, Somnath, Suhas, additional, Holt, Adam P., additional, Ovchinnikova, Olga S., additional, Jesse, Stephen, additional, Martin, Halie, additional, Etampawala, Thusitha, additional, Dadmun, Mark, additional, and Sokolov, Alexei P., additional

Published
2016
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21. Unexpected Molecular Weight Effect in Polymer Nanocomposites

Author

Cheng, Shiwang, primary, Holt, Adam P., additional, Wang, Huiqun, additional, Fan, Fei, additional, Bocharova, Vera, additional, Martin, Halie, additional, Etampawala, Thusitha, additional, White, B. Tyler, additional, Saito, Tomonori, additional, Kang, Nam-Goo, additional, Dadmun, Mark D., additional, Mays, Jimmy W., additional, and Sokolov, Alexei P., additional

Published
2016
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22. Direct Air Capture of CO2with Aqueous Amino Acids and Solid Bis-iminoguanidines (BIGs)

Author

Custelcean, Radu, Williams, Neil J., Garrabrant, Kathleen A., Agullo, Pierrick, Brethomé, Flavien M., Martin, Halie J., and Kidder, Michelle K.

Abstract

We report a bench-scale direct air capture (DAC) process comprising CO2absorption with aqueous amino acid salts (i.e., potassium glycinate, potassium sarcosinate), followed by room-temperature regeneration of the amino acids by reaction with solid meta-benzene-bis(iminoguanidine) (m-BBIG), resulting in crystallization of the hydrated m-BBIG carbonate salt, (m-BBIGH2)(CO3)(H2O)n(n= 3–4). The CO2is subsequently released by mild heating (60–120 °C) of the carbonate crystals, which regenerates the m-BBIG solid quantitatively. This low-temperature crystallization-based DAC process circumvents the need to heat the aqueous amino acid sorbents, thereby minimizing their loss through thermal and oxidative degradation. The CO2cyclic capacity for the sarcosine/m-BBIG system, measured over three consecutive absorption/regeneration cycles, is in the range of 0.12–0.20 mol/mol. The regeneration energy of m-BBIG, comprising the enthalpy of CO2and water release, and the sensible heat, is 360 kJ/mol (8.2 GJ/ton CO2). Alternatively, the aqueous amino acids can be regenerated by boiling under reflux, with measured cyclic capacities of up to 0.64 mol/mol.

Published
2019
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25. Controlling Interfacial Dynamics: Covalent Bonding versusPhysical Adsorption in Polymer Nanocomposites

Author

Holt, Adam P., Bocharova, Vera, Cheng, Shiwang, Kisliuk, Alexander M., White, B. Tyler, Saito, Tomonori, Uhrig, David, Mahalik, J. P., Kumar, Rajeev, Imel, Adam E., Etampawala, Thusitha, Martin, Halie, Sikes, Nicole, Sumpter, Bobby G., Dadmun, Mark D., and Sokolov, Alexei P.

Abstract

It is generally believed that the strength of the polymer–nanoparticle interaction controls the modification of near-interface segmental mobility in polymer nanocomposites (PNCs). However, little is known about the effect of covalent bonding on the segmental dynamics and glass transition of matrix-free polymer-grafted nanoparticles (PGNs), especially when compared to PNCs. In this article, we directly compare the static and dynamic properties of poly(2-vinylpyridine)/silica-based nanocomposites with polymer chains either physically adsorbed (PNCs) or covalently bonded (PGNs) to identical silica nanoparticles (RNP= 12.5 nm) for three different molecular weight (MW) systems. Interestingly, when the MW of the matrix is as low as 6 kg/mol (RNP/Rg= 5.4) or as high as 140 kg/mol (RNP/Rg= 1.13), both small-angle X-ray scattering and broadband dielectric spectroscopy show similar static and dynamic properties for PNCs and PGNs. However, for the intermediate MW of 18 kg/mol (RNP/Rg= 3.16), the difference between physical adsorption and covalent bonding can be clearly identified in the static and dynamic properties of the interfacial layer. We ascribe the differences in the interfacial properties of PNCs and PGNs to changes in chain stretching, as quantified by self-consistent field theory calculations. These results demonstrate that the dynamic suppression at the interface is affected by the chain stretching; that is, it depends on the anisotropy of the segmental conformations, more so than the strength of the interaction, which suggests that the interfacial dynamics can be effectively tuned by the degree of stretchinga parameter accessible from the MW or grafting density.

Published
2016
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26. Neutron Scattering Studies of Nanoscale in Functional Polymeric Materials

Author

Martin, Halie Jill

Abstract

This dissertation presents work that expands our understanding of the relationship between structure, conformation, and topology and the properties and dynamics of polymeric materials. These studies focus on novel soft polystyrene and poly (butyl acrylate) nanoparticles and the polyradical poly (2,2,6,6-tetramethylpeperidinyloxy-4-yl methacrylate) (PTMA). Small angle neutron scattering characterizes the structural features of these polymeric materials. These studies provide integral insight that may be used to improve the performance of functional polymers by elucidating a molecular structure:property relationship.The first two projects of this dissertation examined the correlation of synthetic conditions to the structural characteristics of soft nanoparticles. The precise structure of the soft nanoparticles can be tailored by utilizing monomer-starved semi batch nanoemulsion polymerizations. The results correlate synthetic conditions to the individual soft nanoparticle size, internal structure, and overall topology. The correlation between the size and morphology of soft nanoparticles and solvent quality was also emphasized. This research provides a pathway to investigate the effect of nanoscale structural features of the nanoparticle on their individual properties and those of nanocomposites that contain these soft nanoparticles.The dynamics of all-polymer polystyrene nanocomposites through in-situ neutron scattering were also investigated. The addition of soft nanoparticles slowed the diffusion of the matrix polymer chains when the nanoparticles were larger than the polymer and had no significant effect when the nanoparticles were of similar size to the linear polymer. When the soft nanoparticles were smaller than the polymer chains, the nanoparticles enhanced the overall polymer diffusion.Finally, the effect of radical concentration on the conformation of PTMA was examined. In this study, the radical concentration was determined to influence the reorientation of polymer chains in order to increase the amount of radical interactions between neighboring chains. However, when the radical concentration was low, the oxidation of the stable radical groups results in a greater structural reorganization. This structure reorientation knowledge may be utilized to optimize redox active radical polymers for organic radical battery device applications.

Published
2018

27. Unexpected Molecular Weight Effect in Polymer Nanocomposites.

Author

Shiwang Cheng, Holt, Adam P., Huiqun Wang, Fei Fan, Bocharova, Vera, Martin, Halie, Etampawala, Thusitha, White, B. Tyler, Tomonori Saito, Nam-Goo Kang, Dadmun, Mark D., Mays, Jimmy W., and Sokolov, Alexei P.

Subjects
*POLYMERIC nanocomposites, *INTERFACES (Physical sciences), *MOLECULAR weights
Abstract

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]

Published
2016
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28. Dialing in Direct Air Capture of CO 2 by Crystal Engineering of Bisiminoguanidines.

Author

Custelcean R, Williams NJ, Wang X, Garrabrant KA, Martin HJ, Kidder MK, Ivanov AS, and Bryantsev VS

Abstract

Direct air capture (DAC) technologies that extract carbon dioxide from the atmosphere via chemical processes have the potential to restore the atmospheric CO 2 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 CO 2 , 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., (© 2020 Wiley‐VCH GmbH.)

Published
2020
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