Rings and loops in perflurosurfactants viscoelastic solutions

The structure of micellar solutions has been a topic of intense research. Of particular interest is the relation between rheological properties and the nanostructure of the corresponding micelles. At compositions surrounding the 2nd CMC, the onset of micellar growth, spherical micelles typically transition into short rodlike micelles, and these assemblies continue to grow into long, entangled threadlike micelles, avoiding micellar ends. Another possibility to avoid unfavorable micellar ends is to form small closed structures—rings and loops. Here, we disclose with cryo-TEM the formation of these assemblies near the 2nd CMC, for a perfluorosurfactant C 8 F 17 SO 3 N(C 2 H 5 ) 4 , and we correlate the observations with electric birefringence (EB) data that show 4 separate processes near that critical composition.