The Influence of Polyampholytes on the Phase Behavior of Microemulsion Used as Template for the Nanoparticle Formation

Abstract

A series of hydrophobically modified polyampholytes has been synthesized by the copolymerization of the cationic monomer (N,N′‐diallyl‐N,N′‐dimethylammonium chloride) and the anionic monomers maleamic acid or butylmaleamic acid, and their influence on the inverse micellar region of the quaternary system sodium dodecylsulfate/toluene‐pentanol (1:1)/water has been investigated. The polymers increase the water solubilization capacity of the microemulsion at a polymer concentration ≥5%. However, the polyampholyte‐modified inverse microemulsions show a temperature dependent behavior, by the formation at 40°C of a narrow bicontinuous channel between the L₂ (w/o) and the L₁ (o/w) microemulsion phases. In this case, hydrophobic interactions between the surfactant alkyl tails and the hydrophobic side chains of the copolymer play an important role, too. The reverse microemulsion droplets were used as a template for the synthesis of BaSO₄ nanoparticles. The polymers, which are involved in the redispersion process, influence the size and the stability of the nanoparticles formed by preventing their aggregation. Finally, monodisperse BaSO₄ nanoparticles with an average size of 5 nm, thus, can be recovered and characterized by dynamic light scattering, zeta potential measurements, and transmission electron microscopy.

Keywords:

• Polyelectrolytes
• microemulsion
• nanoparticles

The authors thank Prof. A. Laschewsky, University of Potsdam & Fraunhofer Institut für Angewandte Polymerforschung (Golm), for providing access to his synthesis laboratories and for fruitful discussions on polymer synthesis. Dr. B. Tiersch and Frau S. Rüstig,University of Potsdam, are acknowledged for the TEM and Cryo‐SEM micrographs.