Computational Study of Microhydration in Sulfonated Diels–Alder Poly(phenylene) Polymers

Journal Article · Wed Mar 28 00:00:00 EDT 2018 · Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory

DOI:https://doi.org/10.1021/acs.jpca.8b01354· OSTI ID:1469631

Alam, Todd M.  ^[1]

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1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Dept. of Organic Material Science

In this paper, the nature of microhydration in sulfonated Diels–Alder poly(phenylene) (SDAPP) polymer membranes is explored using ab initio and density functional theory (DFT) electronic structure calculations. The impact of the aromatic poly(phenylene) structure, including cooperative effects between multiple spatially adjacent sulfonic groups, on the hydration environment is addressed using a series of DFT B3LYP/6-311**-optimized structures for different SDAPP·nH₂O clusters. In addition, larger SDAPP polymer fragments, along with selected hydrophilic domain structures extracted from molecular dynamic (MD) simulations, are also evaluated using ONIOM HF/PM6 semiempirical calculations. The SDAPP clusters reveal that spontaneous proton dissociation occurs at low levels of hydration to form sulfonic-acid-associated H₃O⁺ contact ion pairs (CIPs), which then evolve into solvated CIPs at higher hydration levels. For multiple sulfonic acid groups located on the poly(phenylene) side chains, the hydration energies are a function of the relative acid location and backbone configuration. Variations in the phenylene backbone torsional angles allow remote sulfonic acids to adopt an optimal separation to produce an extended hydrogen bonded network of waters between the SDAPP acids groups. Finally, these calculations provide a baseline to help describe the proton transport and hydration behavior of SDAPP membranes.

• Research Organization: Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA); SNL Laboratory Directed Research and Development (LDRD) Program
• Grant/Contract Number: NA0003525
• OSTI ID: 1469631
• Report Number(s): SAND2018-1994J; 660911
• Journal Information: Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory, Vol. 122, Issue 15; ISSN 1089-5639
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: English

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