Spherical Supramolecular Minidendrimers Self-Organized in an “Inverse Micellar”-like Thermotropic Body-Centered Cubic Liquid Crystalline Phase

Abstract

An “inverse micellar”- or “water-in-oil”-like (similar to the lyotropic type III) thermotropic body-centered cubic (BCC) liquid crystal (LC) phase was discovered in a poly(ethyleneimine) with a degree of polymerization (DP) = 20 containing 3,4,5-tri(dodecyloxy)benzoyl minidendritic side groups. Fiber X-ray diffraction (XRD) experiments show that the extinction symbol of this phase is I- - - and, alongside other evidence, suggested that the space group is Im3̄m (Q229). These results point to a supramolecular inverse micellar-like structure with the polymer backbone and the benzoyl groups aggregated into globules located at the corners and the center of the unit cell. The n-alkyl groups radiate out of the aromatic part of the globule and make up the continuos matrix of the lattice. The cubic unit cell parameter is a = 42.6 Å. Upon shearing, the BCC phase aligns along the [111] direction. The BCC lyotropic Im3̄m inverse micellar phase of III type has not yet been observed and the experiments reported here will access its design. The present is only the second “inverse micellar” thermotropic LC phase known. The first one was previously reported from our laboratories (Balagurusamy, V. S. K.; Ungar, G.; Percec, V.; Johansson, G. J. Am. Chem. Soc. 1997, 119, 1539) and has a Pm3̄n symmetry. Both the Im3̄m and the Pm3̄n cubic lattices were self-organized from spherical supramolecular dendrimers. The BCC cubic LC lattice reported here enriches the synthetic capabilities of dendritic building blocks.