Solid‐State Hosts by the Template Polymerization of Columnar Liquid Crystals: Locked Supramolecular Architectures around Chiral 2‐Amino Alcohols

Abstract

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.

Hydrogen Bonding in Supramolecular Nanoporous Materials

“…These results showed that Hbonding interactions can be used to bind guest molecules in materials by molecular imprinting. More recent studies have demonstrated that the polymer porous material also readily incorporates other guest molecules with sizes that fit in the chiral nanochannels [67]. Detailed studies indicate that modification of the polymer porous material has large effects on properties such as structural order, guest recognition and release, and its repetitive switching [64,68].…”

Organic Zeolite Analogues Based on Multi-Component Liquid Crystals: Recognition and Transformation of Molecules within Constrained Environments

“…Therefore, in situ reactions in LCs would lead to a new type of tailored micro-environment, which may realize highly efficient/selective molecular recognitions and chemical reactions. This review summarizes our recent effort to develop a new class of micro-environment based on the in situ reactions in LCs [16,17,18,19,20]. In relation to our studies, we also provide an overview of notable works related to LC-template reactions, from historically important reports to recent trends.…”

Challenges and breakthroughs in recent research on self-assembly

“…Clark and coworkers reported a class of fluid polar smectic liquid crystals in which local splay prevails in the form of periodic supermolecular-scale polarization modulation stripes coupled to layer undulation waves [216]. Other recent examples on self-assembled liquid crystal materials are also available [217][218][219][220][221].…”