Dynamics of amphiphilic surfactants confined in montmorillonite slits with different cation exchange capacities

Georgios Polizos, Richard A. Vaia, Hilmar Koerner, Evangelos Manias

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Alkylammonium surfactants were nanoscopically confined between montmorillonite layers of varied negative surface charge, i.e., of varied cation exchange capacities. Dielectric relaxation spectroscopy was employed to probe the interfacial dynamics, arising from the mobility of the cations on the silicate surfaces, as a function of the confining walls' surface charge. Standard methods to dry the organo-silicates were employed; however, water was still detected physisorbed in the galleries; the dynamics of these water molecules were also detected and were found to be coupled with the dynamics of the ammoniums at high temperatures. A transition in the mobility of the cations, approximately at 75 C (which is in good agreement with the conformational changes of the alkyl groups, reported in the literature), is observed, and a model is proposed on the basis of the dynamics of the confined water. Entropic contributions arising from variation in the surface charge density are also discussed in detail. The existence of water in the interlayer - in spite of drying the nanofillers in accordance to industrial practices - and the interrelated surfactant/water dynamics bring forward important implications for the design and processing of polymer-based nanocomposites based on these fillers.

Original languageEnglish (US)
Pages (from-to)13667-13678
Number of pages12
JournalJournal of Physical Chemistry B
Volume117
Issue number43
DOIs
StatePublished - Oct 31 2013

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Bentonite
montmorillonite
Clay minerals
Surface-Active Agents
slits
Cations
Ion exchange
Surface active agents
Positive ions
surfactants
cations
Surface charge
Water
Silicates
water
silicates
Dielectric relaxation
Charge density
fillers
confining

All Science Journal Classification (ASJC) codes

  • Surfaces, Coatings and Films
  • Physical and Theoretical Chemistry
  • Materials Chemistry

Cite this

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abstract = "Alkylammonium surfactants were nanoscopically confined between montmorillonite layers of varied negative surface charge, i.e., of varied cation exchange capacities. Dielectric relaxation spectroscopy was employed to probe the interfacial dynamics, arising from the mobility of the cations on the silicate surfaces, as a function of the confining walls' surface charge. Standard methods to dry the organo-silicates were employed; however, water was still detected physisorbed in the galleries; the dynamics of these water molecules were also detected and were found to be coupled with the dynamics of the ammoniums at high temperatures. A transition in the mobility of the cations, approximately at 75 C (which is in good agreement with the conformational changes of the alkyl groups, reported in the literature), is observed, and a model is proposed on the basis of the dynamics of the confined water. Entropic contributions arising from variation in the surface charge density are also discussed in detail. The existence of water in the interlayer - in spite of drying the nanofillers in accordance to industrial practices - and the interrelated surfactant/water dynamics bring forward important implications for the design and processing of polymer-based nanocomposites based on these fillers.",
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Dynamics of amphiphilic surfactants confined in montmorillonite slits with different cation exchange capacities. / Polizos, Georgios; Vaia, Richard A.; Koerner, Hilmar; Manias, Evangelos.

In: Journal of Physical Chemistry B, Vol. 117, No. 43, 31.10.2013, p. 13667-13678.

Research output: Contribution to journalArticle

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