Molecular clustering in formaldehyde−methanol−water mixtures revealed by high-intensity, high‑Q small-angle neutron scattering

Swarit Dwivedi, Jitendra Mata, Samir H. Mushrif, Alan L. Chaffee, Akshat Tanksale

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Methanol−Water (mw) mixtures, with or without a solute, display a nonideal thermodynamic behavior, typically attributed to the structure of the microphase. However, experimental observation of the microphase structures at the molecular length scale has been a challenge. We report the presence of molecular clusters in mw and formaldehyde−methanol−water (fmw) mixtures using small-angle neutron scattering (SANS) experiments and molecular dynamics (MD) simulations. Hydrophobic clusters of methanol in mw and formaldehyde−methanol in fmw mixtures were observed at low methanol compositions (xm ≤ 0.3). A three-dimensional hydrogen-bonded network of water with the solute is observed at xm = 0.5. Linear chains of methanol surrounding the formaldehyde and water molecules were observed at high methanol compositions (xm ≥ 0.7). The calculated size of the molecular clusters (r ≈ 0.5 nm, spherical) from the SANS data and their volume fraction closely matched the MD simulation results.

Original languageEnglish
Pages (from-to)480-486
Number of pages7
JournalJournal of Physical Chemistry Letters
Issue number1
Publication statusPublished - 2021

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