Temperature-induced intermicellization and contraction in aqueous mixtures of sodium dodecyl sulfate and an amphiphilic diblock copolymer

  • Ramón Pamies /
  • Kaizheng Zhu /
  • Anna Lena Kjøniksen /
  • Kenneth D. Knudsen /
  • Bo Nyström
Journal ar
Journal of Colloid and Interface Science
  • Volumen: 326
  • Número: 1
  • Fecha: 01 October 2008
  • Páginas: 76-88
  • ISSN: 00219797
  • Source Type: Journal
  • DOI: 10.1016/j.jcis.2008.07.039
  • Document Type: Article
Aqueous solutions of a thermoresponsive amphiphilic diblock copolymer, containing poly(N-isopropylacrylamide), in the presence of the anionic sodium dodecyl sulfate (SDS) surfactant can undergo a temperature-induced transition from loose intermicellar clusters to collapsed core-shell nanostructures. The polymer-surfactant mixtures have been characterized with the aid of turbidity, small-angle neutron scattering (SANS), intensity light scattering (ILS), dynamic light scattering (DLS), shear viscosity, and rheo-small angle light scattering (rheo-SALS). In the absence of SDS, compressed intermicellar structures are formed at intermediate temperatures, and at higher temperatures further aggregation is detected. The SANS results disclose a structure peak in the scattered intensity profile at the highest measured temperature. This peak is ascribed to the formation of ordered structures (crystallites). In the presence of a low amount of SDS, a strong collapse of the intermicellar clusters is observed at moderate temperatures, and only a slight renewed interpolymer association is found at higher temperatures because of repulsive electrostatic interactions. Finally, at moderate surfactant concentrations, temperature-induced loose intermicellar clusters are detected but no shrinking was registered in the considered temperature range. At a high level of SDS addition, large polymer-surfactant complexes appear at low temperatures, and these species are compressed at elevated temperatures. The rheo-SALS results show that the transition structures are rather fragile under the influence of shear flow. © 2008 Elsevier Inc. All rights reserved.

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