We have been able to visualize single molecules of cylindrical brushes and perform statistical analysis of their conformation. From the contour length, the local curvature and the end-to-end distance, one could determine the linear density and the persistence length of the molecules. The ability of SFM to acquire the three-dimensional shape enables direct evaluation of the topographic profile and the volume which is occupied by the molecule. Furthermore, the sensitivity of the force signal to different types of local interactions provides a unique possibility to investigate the microstructure and the chemical composition of single molecules with a resolution down to 1 nm.
For the first time, the coexistence of two different conformational states in one molecule has been visualized by scanning force microscopy for a rod-globule transition of brush molecules. The transition, which occurred upon lateral compression of monolayers, was also examined theoretically by scaling analysis that proved its first order character. The transition becomes less distinct with decreasing length of the side chains and finally vanishes below a certain critical value.
Wetting stability of polymers with perfluorinated side chains is of practical importance for oil-, water and soil repellent coatings for textiles and polymers as well as for the coating technology itself. Our recent study has shown that semifluorinated polymers undergo layer-by-layer autophobic dewetting. This phenomenon is controlled by interplay between entropically favorable coiling of the backbone and energetically favored ordering of the side chains. Film stability and kinetics of the dewetting process is studied systematically in dependence of the polymer structure, film thickness and interaction with the substrate.
