Nanoporous Supramolecular Liquid Crystal Polymeric Material for Specific and Selective Uptake of Melamine

Abstract

Nanoporous materials derived from hydrogen-bonded supramolecular liquid crystal complexes present a promising and prevalent perspective in selective adsorption, water desalination, ion conductivity, and so on. However, the specific recognition and selective uptake of some highly self-complementary hydrogen-bonded heterocyclic compounds (e.g., melamine) are extremely difficult for the widely used carboxylic acid-type discotic liquid crystals to competitively bind and remain challenging. Here, we report a nanoporous supramolecular liquid crystal polymeric material built on a photo-cross-linked melamine/thymine-derivative supramolecular structure, which can specifically recognize and selectively absorb melamine from solutions. The small pore diameter, specific hydrogen-bonded sites, and strong systematic binding in the hexagonal columnar nanochannels of the supramolecular polymeric material endow itself with a series of superior properties, including highly competitive uptake of melamine, stable adsorption even in harsh environments, and good adsorption recyclability. Moreover, the melamine adsorption capacity and kinetics of the supramolecular material are also investigated, which determines that the adsorption kinetics of the nanoporous liquid crystal polymeric material follow the Lagergren pseudo-second-order kinetic model.

Hydrogen-Bonded Supramolecular Liquid Crystal Polymers: Smart Materials with Stimuli-Responsive, Self-Healing, and Recyclable Properties

“…(d) Chemical structure of the melamine-thymine-functionalized gallic acid hydrogen-bonded complex. Adapted with permission from ref ( 70 ). Copyright 2020 American Chemical Society.…”

“…(e) Schematic representation of the self-assembly into the columnar phase, polymerization, and removal of the thymine core resulting in a 1D nanostructured material with high selectivity toward the original host. Adapted with permission from ref ( 70 ). Copyright 2020 American Chemical Society.…”

“…The use of thymine-derived side units resulted in the formation of complex 36 with triple hydrogen bonds, leading to higher selectivity toward the templated core molecule ( Figure 19 d). 70 The complex consisting of melamine and three thymine acrylate functionalized derivatives resulted in a hexagonal columnar mesophase. Subsequent photopolymerization and removal of the melamine template core resulted in nanoporous melamine imprinted channels.…”

Smectic Liquid Crystalline Polymer Membranes with Aligned Nanopores in an Anisotropic Scaffold

“…Liquid crystal (LC)-based polymer membranes have been investigated due to their numerous phases, ease of fabrication, high order, and variety in chemical composition. Thus, 1D nanochannels, 12 , 13 , 17 − 25 2D-layered systems, 12 , 26 − 29 and 3D bicontinuous phases 30 − 32 have been reported. For the fabrication of free-standing LC polymer films, typical polymerization is performed inside an LC cell having alignment layers.…”

Smart Supramolecular Self-Assembled Nanosystem: Stimulus-Responsive Hydrogen-Bonded Liquid Crystals

“…Finally, different columnar mesomorphic orders (e.g., hexagonal, rectangular and square columnar phases) were obtained by adding functional thymine or succinimide units, and changing the molar ratios of melamine to those of H-bonded complementary compounds. Subsequently, this group reported a nanoporous supramolecular H-bonded LC polymer based on a melamine/thymine derivative for the specific recognition and absorption of melamine (see Figure 10 ) [ 141 ]. It showed a stable and recyclable absorbability of melamine within a wide pH range (pH 4~10).…”