Supramolecular self-assembly of two-component systems comprising aromatic amides/Schiff base and tartaric acid
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RESEARCH ARTICLE
Supramolecular self-assembly of two-component systems comprising aromatic amides/Schiff base and tartaric acid Xin Wang, Wei Cui, Bin Li, Xiaojie Zhang, Yongxin Zhang, Yaodong Huang (✉) Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin 300350, China
© Higher Education Press 2020
Abstract The gelating properties and thermotropic behaviors of stoichiometric mixtures of aromatic amides 1, 2, and the aromatic Schiff base 3 with tartaric acid (TA) were investigated. Among the three gelators, 2-TA exhibited superior gelating ability. Mixture 2-TA exhibits a smectic B phase and an unidentified smectic mesophase during both heating and cooling runs. The results of Fourier transform infrared spectroscopy and X-ray diffraction revealed the existence of hydrogen bonding and p-p interactions in 2-TA systems, which are likely to be the dominant driving forces for the supramolecular selfassembly. Additionally, it was established that all of the studied gel self-assemblies and mesophases possess a lamellar structure. The anion response ability of the tetrahydrofuran gel of 2-TA was evaluated and it was found that it was responsive to the stimuli of F–, Cl–, Br–, I–, AcO–. Keywords supramolecular self-assembly, organogel, liquid crystal, tartaric acid, hydrogen bond
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Introduction
A supramolecular assembly is a complex array of molecules with a well-defined structure, held together by non-covalent bonds, which include hydrogen bonds, p-p stacking, halogen bonds, solvophobic interactions, van der Waals forces, host-guest interactions, dipole-dipole interactions, and coordination bonds, etc. The two most significant soft materials generated from supramolecular assemblies, supramolecular gels (SGs) and liquid crystals (LCs), have been exploited for various applications. SGs
Received April 20, 2019; accepted May 28, 2019 E-mail: [email protected]
and LCs can be one-component, two-component or even multi-component assemblies. Recently, two-component supramolecular assemblies have garnered considerable research interests because they possess an additional level of functionality, tunability and control [1–3], which is critical for real applications. For example, two-component gels containing tartaric acid have important applications in organic light emitting devices, chiral discrimination, photoluminescent materials, and chiral helix induction, among other fields [4–7]. Hydrogen bonding plays an essential role in supramolecular assemblies and has therefore been broadly applied to SGs and LCs, both in one-component and twocomponent systems. The most convenient approach for preparing a two-component self-assembly is by mixing the two components, which can interact through hydrogen bonding. Currently, there are a number of reports in the literature describing hydrogen bonding as the driving force for self-assembly or aggregation [8–11]. Tartaric acid (TA) is a common low cost compound with a symmetrical structure bearing two
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