Nanosheets Based on Hard 2-Ureido-4[1H]-pyrimidone Units and Soft Cyclosiloxane Units as Membrane Materials

Abstract

Two-dimensional (2D) nanomaterials have attracted great attention in recent years because of their unique physical, optical, chemical, and electronic properties, and their great potential for use in various applications such as gas and chemical sensors based on nanomaterials. Particularly, two-dimensional materials provide excellent sensitivity because of nanoscale-specific characteristics such as a large surface-to-volume ratio, good room-temperature mobility, and chemical stability. Their hydrophobic and hydrophilic components combined with supramolecular assembly properties are anticipated to prepare organic and organic–inorganic hybrid 2D nanomaterials with a large area and high quality. As described herein, we designed and synthesized a hybrid small molecule, designated as HMCS-UPy, that combines two components through an alkyl linker: (1) 2-ureido-4­[1H]-pyrimidone (UPy) units, which are dynamic and hard segments with multiple hydrogen bonding sites; and (2) soft cyclosiloxane (HMCS) units, which are hydrophobic and incompatible with other chemical groups. The HMCS-UPy molecules underwent self-assembly to form a large-area nanosheet with a lamellar structure and 2.9 nm layer thickness through a simple solution process driven by a soft–hard microphase separation and multiple hydrogen bonding interactions. Findings also indicate the nanosheet assembly formation as based on 2D sheets consisting of UPy dimer planes and indicate microphase separation of soft HMCS and hard UPy regions.

Urea-Functionalized Heterocycles: Structure, Hydrogen Bonding and Applications

“…Hydrogen bonds remained undisturbed even in water due to the shielding effect of the hydrophobic π-stacking pockets of quinolone [43]. As another example, aggregation of the molecules of UPy derivative 76 (Figure 26), bearing a cyclo-siloxane moiety as the hydrophobic unit, led to the formation of large-area nanosheets with a lamellar structure [93]. Another switchable assembly was developed based on monomer 74 (Figure 24) that adopted the tetrameric form in CDCl 3 [91].…”