Solid-state hosts by the template polymerization of columnar liquid crystals: locked supramolecular architectures...

The cross-linking of multicomponent liquid crystals could be applied to the synthesis of nanometer-sized porous materials with a well-defined structure. In this work we demonstrate the template polymerization of columnar liquid crystals composed of the salts of a carboxylic acid and enantiopure 2-amino alcohols, and the application of one of them as a solid-state host. The salts of 3,4,5-tris(11-acryloyloxyundecyloxy)benzoic acid with (S)-2-amino-1-propanol and with (1R,2S)-norephedrine showed hexagonal and rectangular columnar liquid-crystalline structures, respectively. The successful application of gamma-ray-induced polymerization to the cross-linking of the liquid-crystalline salts, which was more advantageous than photoinduced polymerization from the standpoint of the retention of the original structural order in the gram-scale preparation of the polymers with a homogeneous columnar structure. The cross-linked polymer thus obtained from the gallic acid derivative and (1R,2S)-norephedrine was applicable as a heterogeneous host to capture amines from a guest solution through acid-amine interactions. When (1R,2S)-norephedrine was replaced with other amines through the guest-exchange reaction, a "template effect" was observed; the size and shape of the guests were determining factors for the efficiency of the guest exchange. The guest adsorption was found to proceed in an enantioselective manner when racemic 2-amino alcohols were used as guests, especially in the cases of substrates possessing a bulky substituent at the C1-position. The guest preference was again elucidated by the template effect, although the enantioselection mode was switched depending on the presence of a C2 substituent.