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Viscoelastic Synergy and Microstructure Formation in Aqueous Mixtures of Nonionic Hydrophilic Polymer and Charged Wormlike Surfactant Micelles
journal contribution
posted on 2016-12-20, 17:59 authored by Andrey V. Shibaev, Ksenia A. Abrashitova, Alexander I. Kuklin, Anton S. Orekhov, Alexander L. Vasiliev, Ilias Iliopoulos, Olga E. PhilippovaWe studied the effect of neutral
polymer poly(vinyl alcohol) on the rheological properties and microstructure
of highly charged mixed wormlike micelles of anionic and cationic
surfactants, potassium oleate and n-octyltrimethylammonium
bromide, without adding salt. It was shown that the polymer induces
a hundredfold increase of viscosity and of longest relaxation time
and the appearance of well-defined plateau modulus, which was assigned
to interlacing of polymer and micellar chains. When the amount of
added polymer exceeds 2 wt %, the rheological characteristics (the
viscosity, the longest relaxation time, and the plateau modulus) level
off because of microphase separation appearing as a result of the
interplay of the segregation on the microscopic scale triggered by
the energetic repulsion between polymer and surfactant components,
on the one hand, and the translational entropy of counterions preventing
the macroscopic phase separation, on the other hand. The formation
of surfactant-rich and polymer-rich microphases was evidenced by small-angle
neutron scattering and cryogenic transmission electron microscopy
data. The results obtained open a new way to modify the rheological
properties and the microstructure of wormlike micellar solutions.