Premium
Spontaneous Hierarchical Assembly of Crown Ether‐like Macrocycles into Nanofibers and Microfibers Induced by Alkali‐Metal and Ammonium Salts
Author(s) -
Hui Joseph K.H.,
Frischmann Peter D.,
Tso ChienHsin,
Michal Carl A.,
MacLachlan Mark J.
Publication year - 2010
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200902712
Subject(s) - crown ether , alkali metal , ammonium , microfiber , nanofiber , polymer chemistry , materials science , ether , crown (dentistry) , chemistry , chemical engineering , organic chemistry , nanotechnology , composite material , ion , engineering
Schiff base macrocycle 1 , which has a crown ether like central pore, was combined with different alkali‐metal and ammonium salts in chloroform, resulting in one‐dimensional supramolecular aggregates. The ion‐induced self‐assembly was studied with solid‐state NMR spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). It was found that the lengths and widths of the superstructures depend on the cation and counteranion of the salts. Among the salts being used, Na + and NH 4 + ions with BF 4 − ions showed the most impressive fibrous structures that can grow up to 1 μm in diameter and hundreds of microns in length. In addition, the size of the fibers can be controlled by the evaporation rate of the solvent. A new macrocycle with bulky triptycenyl substituents that prevent supramolecular assembly was prepared and did not display any nanofibers with alkali‐metal ions in chloroform when studied with TEM.