Micelle Formation in Langmuir Films of C₆₀Derivatives

Langmuir and Langmuir-Blodgett films of three new amphiphilic [60]fullerene derivatives have been investigated. The molecular design of these compounds was chosen to control the position of the C-60 core relative to the water and to strongly influence the resulting physical properties. The first compound (MonoC8) is a methanofullerene, whereas the two other compounds (BisC8 and BisC12) are C-60 cis-2-bis adducts. All of these compounds form stable Langmuir films. Even though the isotherms show some hysteresis, it was possible to transfer the films onto solid substrates, with the Langmuir-Blodgett method for two compounds and the Langmuir-Schaeffer technique for the last one. Grazing-incidence X-ray analysis indicates that LB films have a low roughness, i.e., are of good quality. MonoC8 forms monolayers, whereas the structure of the films of the two other compounds is more complex, with a micellar substructure within the film. These results show how sensitive the molecular design is to the molecular arrangement and to the conformation of the molecules in the films.