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Title: From aggregative adsorption to surface depletion: Aqueous systems of C nE m amphiphiles at hydrophilic surfaces

Adsorption of a short-chain nonionic amphiphile (C 6E 3) at the surface of mesoporous silica glass (CPG-10) was studied by a combination of adsorption measurements and mesoscale simulations. Adsorption measurements covering a wide composition range of the C 6E 3 + water system show that no adsorption occurs up to the critical micelle concentration (cmc), at which a sharp increase of adsorption is observed that is attributed to ad-micelle formation at the pore walls. Intriguingly, as the concentration is increased further, the surface excess of the amphiphile begins to decrease and eventually becomes negative, which corresponds to preferential adsorption of water rather than amphiphile at high amphiphile concentrations. The existence of such a surface-azeotropic point has not previously been reported in the surfactant adsorption field. Dissipative particle dynamics (DPD) simulations were performed to reveal the structural origin of this transition from aggregative adsorption to surface depletion. Finally, the simulations indicate that this transition can be attributed to the repulsive interaction between head groups, causing amphiphilic depletion in the region around the corona of the surface micelles.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [4]
  1. Technische Univ. Berlin, Berlin (Germany); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Univ. of Copenhagen, Copenhagen (Denmark)
  3. Heriot-Watt Univ., Edinburgh (United Kingdom)
  4. Technische Univ. Berlin, Berlin (Germany)
Publication Date:
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Molecular Physics
Additional Journal Information:
Journal Volume: 1; Journal Issue: 1; Journal ID: ISSN 0026-8976
Publisher:
Taylor & Francis
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; adsorption; ad-micelles; surface azeotrope; surfactant; mesoscale simulations; nanopores
OSTI Identifier:
1349616