Ion-Specific Confined Water Dynamics in Convex Nanopores of Gemini Surfactant Lyotropic Liquid Crystals

Grayson L. Jackson, Sriteja Mantha, Sung A. Kim, Souleymane O. Diallo, Kenneth W. Herwig, Arun Yethiraj, Mahesh Mahanthappa

Research output: Contribution to journalArticle

2 Scopus citations

Abstract

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.

Original languageEnglish (US)
Pages (from-to)10031-10043
Number of pages13
JournalJournal of Physical Chemistry B
Volume122
Issue number43
DOIs
StatePublished - Nov 1 2018

How much support was provided by MRSEC?

  • Shared

Reporting period for MRSEC

  • Period 5

PubMed: MeSH publication types

  • Journal Article
  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

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  • Projects

    MRSEC SEED Projects

    11/1/14 → …

    Project: Research project

    University of Minnesota MRSEC (DMR-1420013)

    Lodge, T. P.

    11/1/1410/31/20

    Project: Research project

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