Abstract
Hypothesis: Understanding the rules that control the assembly of nanostructured soft materials at interfaces is central to many applications. We hypothesize that electrolytes can be used to alter the hydration shell of amphiphilic oligomers at the air-aqueous interface of Langmuir films, thereby providing a means to control the formation of emergent nanostructures. Experiments: Three representative salts – (NaF, NaCl, NaSCN) were studied for mediating the self-assembly of oligodimethylsiloxane methylimidazolium (ODMS-MIM+) amphiphiles in Langmuir films. The effects of the different salts on the nanostructure assembly of these films were probed using vibrational sum frequency generation (SFG) spectroscopy and Langmuir trough techniques. Experimental data were supported by atomistic molecular dynamic simulations. Findings: Langmuir trough surface pressure – area isotherms suggested a surprising effect on oligomer assembly, whereby the presence of anions affects the stability of the interfacial layer irrespective of their surface propensities. In contrast, SFG results implied a strong anion effect that parallels the surface activity of anions. These seemingly contradictory trends are explained by anion driven tail dehydration resulting in increasingly heterogeneous systems with entangled ODMS tails and appreciable anion penetration into the complex interfacial layer comprised of headgroups, tails, and interfacial water molecules. These findings provide physical and chemical insight for tuning a wide range of interfacial assemblies.
| Original language | English |
|---|---|
| Pages (from-to) | 552-560 |
| Number of pages | 9 |
| Journal | Journal of Colloid and Interface Science |
| Volume | 669 |
| DOIs | |
| State | Published - Sep 2024 |
Funding
Z. Liu, L. Lin, U. I. Premadasa, Y.-Z. Ma, and B. Doughty performed SFG measurements and analysis. ODMS-MIM+ oligomer synthesis was performed by T. Li and K. Hong. Molecular dynamics simulations were run by J.-M.Y. Carrillo. Z. Liu, C.P. Collier, and J. Katsaras contributed to Langmuir trough measurements and analysis. All authors contributed to manuscript preparation. Funding. L. Lin, U. I. Premadasa, Y.-Z. Ma, and B. Doughty were supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division. J. Katsaras was supported through the Scientific User Facilities Division of the Department of Energy (DOE) Office of Science, sponsored by the Basic Energy Science (BES) Program, DOE Office of Science, under Contract No. DEAC05-00OR22725. T. Li, K. Hong, J.-M.Y. Carrillo, Z. Liu, and C.P. Collier performed work at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility and sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. Langmuir trough measurements were carried out at the Shull Wollan Center, which is associated with the Neutron Scattering Division, Oak Ridge National Laboratory. This research used resources of the Oak Ridge Leadership Computing Facility, which is a DOE Office of Science User Facility supported under Contract DE-AC05-00OR22725. L. Lin, U. I. Premadasa, Y.-Z., Ma, and B. Doughty were supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division. J. Katsaras was supported through the Scientific User Facilities Division of the Department of Energy (DOE) Office of Science , sponsored by the Basic Energy Science (BES) Program, DOE Office of Science, under Contract No. DEAC05-00OR22725 . T. Li, K. Hong, J.-M.Y. Carrillo, Z. Liu, and C.P. Collier performed work at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility and sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. Langmuir trough measurements were carried out at the Shull Wollan Center, which is associated with the Neutron Scattering Division, Oak Ridge National Laboratory. This research used resources of the Oak Ridge Leadership Computing Facility, which is a DOE Office of Science User Facility supported under Contract DE-AC05-00OR22725 .
Keywords
- Langmuir films
- Nanostructure assembly
- Solvation
- Specific ion effects
- Sum frequency generation spectroscopy
- Surface propensity