Spherical supramolecular minidendrimers self-organized in an `inverse micellar'-like thermotropic body-centered cubic liquid crystalline phase

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 Im3 over-bar m (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 continuous matrix of the lattice. The cubic unit cell parameter is a = 42.6 angstroms. Upon shearing, the BCC phase aligns along the [111] direction. The BCC lyotropic Im3 over-bar m 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 and has a Pm3 over-bar n symmetry. Both the Im3 over-bar m and the Pm3 over-bar n cubic lattices were self-organized from spherical supramolecular dendrimers. The BCC cubic LC lattice reported here enriches the synthetic capabilities of dendritic building blocks.