Canopy Dynamics in Nanoscale Ionic Materials

Michael L. Jespersen, Peter A. Mirau, Ernst von Meerwall, Richard A. Vaia, Robert Rodriguez, Emmanuel P. Giannelis

Research output: Contribution to journalArticlepeer-review

70 Scopus citations

Abstract

Nanoscale ionic materials (NIMS) are organic - inorganic hybrids in which a core nanostructure is functionalized with a covalently attached corona and an ionically tethered organic canopy. NIMS are engineered to be liquids under ambient conditions in the absence of solvent and are of interest for a variety of applications. We have used nuclear magnetic resonance (NMR) relaxation and pulse-field gradient (PFG) diffusion experiments to measure the canopy dynamics of NIMS prepared from 18-nm silica cores modified by an alkylsilane monolayer possessing terminal sulfonic acid functionality, paired with an amine-terminated ethylene oxide/propylene oxide block copolymer canopy. Carbon NMR studies show that the block copolymer canopy is mobile both in the bulk and in the NIMS and that the fast (ns) dynamics are insensitive to the presence of the silica nanoparticles. Canopy diffusion in the NIMS is slowed relative to the neat canopy, but not to the degree predicted from the diffusion of hard-sphere particles. Canopy diffusion is not restricted to the surface of the nanoparticles and shows unexpected behavior upon addition of excess canopy. Taken together, these data indicate that the liquid-like behavior in NIMS is due to rapid exchange of the block copolymer canopy between the ionically modified nanoparticles. © 2010 American Chemical Society.
Original languageEnglish (US)
Pages (from-to)3735-3742
Number of pages8
JournalACS Nano
Volume4
Issue number7
DOIs
StatePublished - Jun 10 2010
Externally publishedYes

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): KUS-C1-018-02
Acknowledgements: Funding provided by the Air Force Office of Scientific Research is gratefully acknowledged. The diffusion portion of this work was supported by the National Science Foundation under Grant No. DMR 04 55117. This publication is based on work supported by Award No. KUS-C1-018-02, made by King Abdullah University of Science and Technology (KAUST). This research was carried out while M. Jespersen was an NRC Postdoctoral Fellow at the Air Force Research Laboratories. We thank H. Koerner and M. Tchoul for assistance with SAXS experiments and GPC experiments, respectively, as well as for productive discussions regarding this research.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.

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