engleski

Effects of Surfactants on Rheological and Morphological Behavior of Symmetric PB-PEO Diblock Copolymer

Symmetric poly(butadiene-b-ethylene oxide) block copolymer (PB-PEO) forms wormlike micelles in water at very low concentrations. Even in dilute solutions wornlike micelles are aggregated showing interesting rheological behavior, shear thickening at the onset of the non-Newtonian regime. At lower shear rates a visible shear banding was observed. The addition of anionic (sodium dodecyl sulfate (SDS)) and zwitterionic (tetradecyl dimethylammoniumpropane sulfonate (TDPS)) surfactants induces structural changes in the size and shape of PB-PEO micelles due to the formation of mixed micelles. Transitions from aggregated to deaggregated state as well as from wormlike to spherical micelles strongly depend on type and surfactant concentration. Structural changes are accompanied first with the viscosity increase and then with viscosity decrease with increasing surfactant concentration. Results presented give a new insight into the role of the surfactant head group molecular characteristic (including cross-sectional area of surfactant head group, the position of each charged groups in the surfactant heads as well as distance of the closest approach of surfactant and its counterions) on the interaction between amphiphilic diblock copolymers and surfactants which is important for better understanding of complex fluids behavior.

diblock copolymer; surfactants; self-assembly

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