Ion-Specific Confined Water Dynamics in Convex Nanopores of Gemini Surfactant Lyotropic Liquid Crystals
| Autor: | Arun Yethiraj, Mahesh K. Mahanthappa, Sung A Kim, Kenneth W. Herwig, Grayson L. Jackson, Souleymane Diallo, Sriteja Mantha |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
Materials science
02 engineering and technology 010402 general chemistry 01 natural sciences Micelle Nanopores Surface-Active Agents X-Ray Diffraction Pulmonary surfactant Scattering Small Angle Materials Chemistry Deuterium Oxide Physical and Theoretical Chemistry chemistry.chemical_classification Small-angle X-ray scattering Sodium Water 021001 nanoscience & nanotechnology Liquid Crystals 0104 chemical sciences Surfaces Coatings and Films Nanopore chemistry Chemical physics Lyotropic liquid crystal Quasielastic neutron scattering Potassium Counterion 0210 nano-technology Porous medium |
| Zdroj: | The Journal of Physical Chemistry B. 122:10031-10043 |
| ISSN: | 1520-5207 1520-6106 |
| DOI: | 10.1021/acs.jpcb.8b05942 |
| Popis: | The impact of pore geometry and functionality on the dynamics of water nanoconfined in porous media are the subject of some debate. We report the synthesis and small-angle X-ray scattering (SAXS) characterization of a series of perdeuterated gemini surfactant lyotropic liquid crystals (LLCs), in which convex, water-filled nanopores of well-defined dimensions are lined with carboxylate functionalities. Quasielastic neutron scattering (QENS) measurements of the translational water dynamics in these dicarboxylate LLC nanopores as functions of the surfactant hydration state and the charge compensating counterion (Na+, K+, NMe4+) reveal that the measured dynamics depend primarily on surfactant hydration, with an unexpected counterion dependence that varies with hydration number. We rationalize these trends in terms of a balance between counterion-water attractions and the nanopore volume excluded by the counterions. On the basis of electron density maps derived from SAXS analyses of these LLCs, we directly show that the volume excluded by the counterions depends on both their size and spatial distribution in the water-filled channels. The translational water dynamics in the convex pores of these LLCs are also slower than those reported in the concave pores of AOT reverse micelles, implying that water dynamics also depend on the nanopore curvature. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|