Supramolecular fullerene polymers and networks directed by molecular recognition between calix[5]arene and C60.

Abstract

A biscalix[5]arene-C60 supramolecular structure was utilized for the development of supramolecular fullerene polymers. Di- and tritopic hosts were developed to generate the linear and network supramolecular polymers through the complexation of a dumbbell-shaped fullerene. The molecular association between the hosts and the fullerene were carefully studied by using (1) H NMR, UV/Vis absorption, and fluorescence spectroscopy. The formation of the supramolecular fullerene polymers and networks was confirmed by diffusion-ordered (1) H NMR spectroscopy (DOSY) and solution viscometry. Upon concentrating the mixtures of di- or tritopic hosts and dumbbell-shaped fullerene in the range of 1.0-10 mmol L(-1) , the diffusion coefficients of the complexes decreased, and the solution viscosities increased, suggesting that large polymeric assemblies were formed in solution. Scanning electron microscopy (SEM) was used to image the supramolecular fullerene polymers and networks. Atomic force microscopy (AFM) provided insight into the morphology of the supramolecular polymers. A mixture of the homoditopic host and the fullerene resulted in fibers with a height of (1.4±0.1) nm and a width of (5.0±0.8) nm. Interdigitation of the alkyl side chains provided secondary interchain interactions that facilitated supramolecular organization. The homotritopic host generated the supramolecular networks with the dumbbell-shaped fullerene. Honeycomb sheet-like structures with many voids were found. The growth of the supramolecular polymers is evidently governed by the shape, dimension, and directionality of the monomers.