Carbosilane dendrimers with perfluoroalkyl end groups. Core-shell macromolecules with generation-dependent order

A series of carbosilane dendrimer generations, G0 to G3, with 4, 12, 36, and 108 end groups, respectively, has been functionalized with perfluorohexyl (C6F13-) groups On the surface. Quantitative perfluoroalkylation of the dendrimer surface was achieved via free radical addition of 3,3,4,3,5,5,6,6,7,7,8,8,8-tridecafluoro-n-octyl mercaptan. Quantitative perfluoroalkylation of the dendrimers was demonstrated by NMR and SEC. The thermal properties of the dendrimers with core-shell structure were investigated by DSC, polarizing microscopy, and WAXS. Whereas GO was obtained as a crystalline material that did not show the formation of mesophases, G1 (12 end groups) exhibited the formation of a highly ordered smectic mesophase between -15 and -30 degrees C. In contrast, G2 and G3 did not form mesophases; however, a transition to a most probably hexagonally ordered array of columns could be observed. The generation-dependent thermal behavior is ascribed to the increasingly dense packing of perfluorohexyl groups on the dendrimer surface.