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Polymer-induced transient networks in water-in-oil microemulsions studied by small-angle x-ray and dynamic light scattering

Blochowicz, T. and Goegelein, C. and Spehr, T. and Müller, M. and Stühn, B. (2007):
Polymer-induced transient networks in water-in-oil microemulsions studied by small-angle x-ray and dynamic light scattering.
In: Physical Review E, 76, (4, Par), [Article]

Abstract

We study water-in-oil microemulsions, in particular dispersions of water droplets coated with a monolayer of the anionic surfactant AOT in a continuous phase of n-decane. Upon addition of the amphiphilic triblock copolymer PEO(polyethylenoxide)-PI(polyisoprene)-PEO, a transient network is formed. At constant droplet size we vary the polymer concentration and there is clear evidence for an increasing crosslinking of the droplets from structural investigations with small-angle x-ray scattering. The dynamics of concentration fluctuations consisting of the translational diffusion of the droplets and the relaxation of the network are monitored with photon correlation spectroscopy. We mainly focus on the variation of the dynamic behavior as a function of the number of polymer molecules per droplet and the droplet volume fraction, which may be taken as a measure for the interdroplet distance. With increasing polymer content the dynamics of the system slows down and three different relaxation processes may be distinguished. We discuss the origin of the different relaxation modes. In particular, it turns out that the intermediate relaxation mode may be suppressed by index matching the oil matrix and the PI block and that it is effectively slowed down by an additional loading of the emulsion droplets with polyethylene glycol of increasing molecular weight.

Item Type: Article
Erschienen: 2007
Creators: Blochowicz, T. and Goegelein, C. and Spehr, T. and Müller, M. and Stühn, B.
Title: Polymer-induced transient networks in water-in-oil microemulsions studied by small-angle x-ray and dynamic light scattering
Language: English
Abstract:

We study water-in-oil microemulsions, in particular dispersions of water droplets coated with a monolayer of the anionic surfactant AOT in a continuous phase of n-decane. Upon addition of the amphiphilic triblock copolymer PEO(polyethylenoxide)-PI(polyisoprene)-PEO, a transient network is formed. At constant droplet size we vary the polymer concentration and there is clear evidence for an increasing crosslinking of the droplets from structural investigations with small-angle x-ray scattering. The dynamics of concentration fluctuations consisting of the translational diffusion of the droplets and the relaxation of the network are monitored with photon correlation spectroscopy. We mainly focus on the variation of the dynamic behavior as a function of the number of polymer molecules per droplet and the droplet volume fraction, which may be taken as a measure for the interdroplet distance. With increasing polymer content the dynamics of the system slows down and three different relaxation processes may be distinguished. We discuss the origin of the different relaxation modes. In particular, it turns out that the intermediate relaxation mode may be suppressed by index matching the oil matrix and the PI block and that it is effectively slowed down by an additional loading of the emulsion droplets with polyethylene glycol of increasing molecular weight.

Journal or Publication Title: Physical Review E
Volume: 76
Number: 4, Par
Divisions: 05 Department of Physics > Institute for condensed matter physics
05 Department of Physics
Date Deposited: 27 Feb 2010 13:39
Identification Number: doi:10.1103/PhysRevE.76.041505
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