Rheologica Acta

, Volume 38, Issue 6, pp 486–494 | Cite as

Rheo-optical investigations of lyotropic mesophases of polymeric surfactants

  • Gudrun Schmidt
  • Stefan Müller
  • Claudia Schmidt
  • Walter Richtering
ORIGINAL CONTRIBUTION

Abstract

The shear orientation of hexagonal and lamellar liquid crystalline phases of polymeric surfactants was investigated by rheo-optical techniques (flow birefringence (Δn), small-angle light scattering) as well as by nuclear magnetic resonance and optical microscopy. The evolution of birefringence in the hexagonal phase is discussed for simple and oscillatory shear, and an alignment of rodlike micelles along the flow direction was found. A shear induced formation of vesicles (“onions”) is observed with the lamellar phase. They displayed a characteristic four-lobe pattern in depolarized light scattering. Above a critical shear stress vesicles were degraded and perpendicularly aligned lamellae (i.e. with their normal along the vorticity direction) were obtained. A comparison of experiments performed at constant stress and constant rate revealed that the vesicle to planar lamellae transition occurred above a critical shear stress. The behavior of the polysoap lyotropic mesophases under shear, i.e. the strain dependent alignment in the hexagonal phase, the shear induced formation of vesicles, and a transition to planar lamellae in the lamellar phase, is very similar to the behavior of lyotropic mesophases formed by low molar mass surfactants or amphiphilic block copolymers. The geometrical constraints that are introduced when amphiphilic side groups are fixed to a polymer backbone do not significantly alter the response of the mesophase to a shear deformation.

Key words Hexagonal Lamellar Vesicle Shear orientation Polymeric surfactant 

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Copyright information

© Springer-Verlag Berlin Heidelberg 1999

Authors and Affiliations

  • Gudrun Schmidt
    • 1
  • Stefan Müller
    • 1
  • Claudia Schmidt
    • 1
  • Walter Richtering
    • 1
  1. 1.Albert-Ludwigs-Universität Freiburg Institut für Makromolekulare Chemie Stefan-Meier-Strasse 31 D-79104 Freiburg, Germany email: rich@uni-freiburg.deDE

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