SEM was additionally performed on the samples 1-5e to analyze the surface of the nanocomposites. The surface was found to be crystal-free for the five samples before thermal annealing, indicating the successful incorporation and confinement of the CP into the polymeric micelles (Figures ). After annealing, some of the samples appeared to have crystalline parts in the SEM images. While the surface of the annealed samples 1e * and 2e * remained crystal-free, crystals were observed for the samples 3e * , 4e * , and 5e * . Interestingly, the presence of crystals on the surface of sample 5e * is less prominent than for the other two samples, which may be an effect of an improved formation of the CP inside the elongated worm-like micelles. To understand the origin of those crystalline parts and to rule out agglomeration and the growth of CP microcrystals outside the polymeric micelles, the nanocomposites were analyzed again by TEM and DLS after annealing. The average hydrodynamic diameters Dh of the re-dispersed samples range from 106 nm ± 67 nm (1e * ) to 246 nm ± 149 nm (5e * ) (Figure ). Particle core sizes and core widths Dcore of the annealed products are 14 nm ± 2 nm (1e * ) to 65 nm ± 5 nm (5e * ) (Figure ). In Table , the comparison of the core size/core width and the hydrodynamic diameter of the assynthesized and the annealed samples is given, showing that very similar results are obtained. Please note that the magnetic properties of samples containing CP SCO microcrystals differ strongly from those of the samples reported here (i.e. bulk-like behavior of as-synthesized samples, see Figure ). This indicates that the crystals found in the SEM measurements are not the bulk iron(II) complex, but of different origin. As illustrated in the SI, (Figures and), the crystals are presumably 4,4'-bipyridine which was used in excess during the synthesis.