Supramolecular Nanofiber Formation of Macrocyclic Dendrimer

Novel macrocyclic dendrimers (Scheme 2), having two cis-1,3,5-cyclohexanetricarboxamide (1) or 1,3,5-benzenetricarboxamide units (3) in their core, were synthesized, and their self-assembly behaviors were evaluated in solution. Infrared spectroscopy of cis-1,3,5-cyclohexanetricarboxamide cored dendrimer (1) in CHCl3 indicated that formation of strong hydrogen-bonding interactions is taking place among the core units. The 1H NMR spectrum of 1 in CDCl3 showed broadenings of all the peaks, which were sharpened by adding one drop of CF3CO2H. GPC analysis showed the formation of self-assembled particles having ultrahigh molecular weight, whose average diameter was evaluated as about 140 nm by DLS measurement. AFM observation of the cast on mica film showed that 1 forms a fibrous assembly of uniform thickness with a diameter of 6 nm. In sharp contrast to 1, 1,3,5-benzenetricarboxamide units cored dendrimer (3) did not form a fibrous assembly under identical conditions because of the twisted arrangement of the core units.