Helical Inversion of Gel Fibrils by Elongation of Perfluoroalkyl Chains as Studied by Vibrational Circular Dichroism

Vibrational circular dichroism (VCD) spectroscopy was applied to gelation by a chiral low‐molecular mass weight gelator, N , N ’‐diperfluoroalkanoyl‐1,2‐ trans ‐diaminocyclohexane. Attention was focused on the winding effects of (–CF 2 ) n chains on the gelating ability. For this purpose, a series of gelators were synthesized with perfluoroalkyl chains of different length ( n = 6–8). When gelation was studied using acetonitrile as a solvent, the fibrils took different morphologies, depending on the chain length: twisted saddle‐like ribbon or helical ribbon from fibril ( n = 6) and a helical ribbon from platelet ( n = 8). The signs of VCD peaks assigned to the couplet of C=O stretching and to the C‐F stretching were also dependent on n , indicating that a gelator molecule changed conformation on elongating perfluoroalkyl chains. A model is proposed for the aggregation modes in fibrils. Chirality 28:361–364, 2016 . © 2016 Wiley Periodicals, Inc.