The Synthesis,Properties And Self-assembly Mechanism Of Supramolecular Gels Based On H₃TTCA And 2,6-pyridinedicar-boxylic Acid Derivatives

Supramolecular gels are composed of organic small molecules,which self-assemble into various entangled 3D nanostructures through noncovalent interactions(such as hydrogen bonds,Van der Waals forces,?-?interactions)to immobilize the solvents and form a gel.With the understanding of the molecular aggregation mode of gelator,attempts are being made to‘design'gelators by combining structural features(for instance,H-bonding motifs such as amino acids,amides,saccharides and ureas)that are known to promote one-dimensional aggregation.In this paper,four organic small molecules,N,N'-di(4-pyridyl)pyridine-2,6-dimethylamide(PBA-N4),triphenylene-2,6,10-tricarboxylic acid(H₃TTCA),N,N'-di(3-pyridyl)pyridine-2,6-dicarboxamide(PBA-N3)and N,N',N"-tri(4-pyridyl)triphenylene-2,6,10-tricarboxamide(NTC-N4)are selected as gelator to prepared their supramolecular gels.Gel self-assembly mechanism and gel properties were studied by FT-IR,rheological techniques.The main research contents and results are as follows:1.The 2,6-pyridine-dicarboxylic acid was selected as the reaction substrate and modified with 4-aminopyridine to obtain an amide derivative N,N'-di(4-pyridyl)pyridine-2,6-dicarboxamide(PBA-N4).PBA-N4 can form thermally reversible supramolecular gels in a variety of organic mixed solvents.Scanning electron microscopy shows that the xerogel had a 3D fibrous structure.The rheological test shows that the gel had good mechanical properties.DSC test shows that the gel system has good thermal stability.Fortunately got single crystal of PBA-N4.By comparing the X ray diffraction results of PBA-N4 crystal and xerogel,it can be seen that the gel and crystal have similar assembly structure.The?-?stacking interaction and intermolecular hydrogen bonds are the main driving forces for their self-assembly.2.The triphenylene-2,6,10-tricarboxylic acid(H₃TTCA)was selected to prepare the supramolecular gel.H₃TTCA insoluble in water but soluble in organic solvents with strong polarity easily,so adding water can cause gelation.The SEM image shows that the gel has a network fiber structure.FT-IR indicates that the gelator interacts through hydrogen bonds between-COOH groups.The results of ¹H NMR show that?-?stacking is also one of the driving forces of gel self-assembly.3.N,N'-di(3-pyridyl)pyridine-2,6-dimethylamide(PBA-N3)were synthesized from2,6-pyridine-dicarboxylic acid and 3-aminopyridine.PBA-N3 forms metallogel with Fe(III),Al(III)and Cr(III).The metllogel has good thermal reversibility.The rheological test shows that the gel has good mechanical strength.The obtained metal gels were characterized by SEM,FT-IR and ¹H NMR.The results shows that PBA-N3 self-assembled into fiber aggregates by metal-ligand interaction,intermolecular hydrogen bonding and?-?stacking in aqueous solution of metal salts such as Fe₂(SO₄)₃.4.The synthesis method of N,N',N"-tri(4-pyridyl)triphenylene-2,6,10-tricarboxamide(NTC-N4)is described in detail.NTC-N4 coordinated with metal to form metallogel in the aqueous solutions of Fe Cl₃,Al Cl₃,and Cr Cl₃.The metal-ligand coordination,intermolecular hydrogen bonding,and?-?stacking are the driving forces of the self-assembly of gelator molecules,which have led to the formation of a 3D network and forming metallogels.The obtained metallogel has good mechanical properties and thermal reversibility.