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Interaction between a water-in-oil microemulsion and a linear-dendritic poly(propylene oxide)–polyglycerol block copolymer

Wipf, R. and Kraska, M. and Spehr, T. and Nieberle, J. and Frey, H. and Stühn, B. (2011):
Interaction between a water-in-oil microemulsion and a linear-dendritic poly(propylene oxide)–polyglycerol block copolymer.
In: Soft Matter, The Royal Society of Chemistry, pp. 10879-10888, 7, (22), [Article]

Abstract

We present small angle scattering and dielectric spectroscopy results on the influence of an amphiphilic diblock copolymer on the structure and dynamics of a microemulsion. We use a water-in-oil (w/o) droplet microemulsion based on the anionic surfactant AOT (sodium bis(2-ethylhexyl) sulfosuccinate), that forms spherical water droplets coated by a monolayer of AOT dispersed in the continuous oil matrix. The studied polymer consists of a hydrophobic poly(propylene oxide) (PPO) block and a hydrophilic hyperbranched polyglycerol with 74 glycerol units (NG74). Combining small angle neutron scattering (SANS) and small angle X-ray scattering (SAXS) we find that the droplet structure is preserved upon addition of PPO-NG74 while the interaction distance between droplets increases with increasing polymer content. From SANS we deduce that the NG74 block is located inside the droplets while the PPO extends into the oil matrix. By measuring the dc-conductivity as a function of temperature we study the dynamic percolation of the microemulsion. While the static structure of the droplet phase remains unchanged, both percolation temperature and phase separation temperature increase linearly with increasing polymer concentration. We explain this finding by a stiffening of the AOT layer induced by the polymer. By means of dielectric spectroscopy we observe two relaxations. The slower one can be related to a polarization at the interface of the water core and the AOT shell (core relaxation) and the faster one is due to the ions in the AOT-shell (cluster relaxation). Polymer addition is found to have a significant influence only on the core relaxation. We apply the cluster relaxation model to estimate the cluster size evolution with increasing polymer concentration.

Item Type: Article
Erschienen: 2011
Creators: Wipf, R. and Kraska, M. and Spehr, T. and Nieberle, J. and Frey, H. and Stühn, B.
Title: Interaction between a water-in-oil microemulsion and a linear-dendritic poly(propylene oxide)–polyglycerol block copolymer
Language: English
Abstract:

We present small angle scattering and dielectric spectroscopy results on the influence of an amphiphilic diblock copolymer on the structure and dynamics of a microemulsion. We use a water-in-oil (w/o) droplet microemulsion based on the anionic surfactant AOT (sodium bis(2-ethylhexyl) sulfosuccinate), that forms spherical water droplets coated by a monolayer of AOT dispersed in the continuous oil matrix. The studied polymer consists of a hydrophobic poly(propylene oxide) (PPO) block and a hydrophilic hyperbranched polyglycerol with 74 glycerol units (NG74). Combining small angle neutron scattering (SANS) and small angle X-ray scattering (SAXS) we find that the droplet structure is preserved upon addition of PPO-NG74 while the interaction distance between droplets increases with increasing polymer content. From SANS we deduce that the NG74 block is located inside the droplets while the PPO extends into the oil matrix. By measuring the dc-conductivity as a function of temperature we study the dynamic percolation of the microemulsion. While the static structure of the droplet phase remains unchanged, both percolation temperature and phase separation temperature increase linearly with increasing polymer concentration. We explain this finding by a stiffening of the AOT layer induced by the polymer. By means of dielectric spectroscopy we observe two relaxations. The slower one can be related to a polarization at the interface of the water core and the AOT shell (core relaxation) and the faster one is due to the ions in the AOT-shell (cluster relaxation). Polymer addition is found to have a significant influence only on the core relaxation. We apply the cluster relaxation model to estimate the cluster size evolution with increasing polymer concentration.

Journal or Publication Title: Soft Matter
Volume: 7
Number: 22
Publisher: The Royal Society of Chemistry
Divisions: 05 Department of Physics > Institute for condensed matter physics > Experimental Condensed Matter Physics
05 Department of Physics > Institute for condensed matter physics
05 Department of Physics
Date Deposited: 11 Apr 2012 06:53
Identification Number: doi:10.1039/C1SM06066J
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