Hierarchical Self-Assembly Of Adhesive And Conductive Gels With Phosphate Anion Coordinated Triple Helicate Junctions

Self-assembly is ubiquitous in biological systems and the basis of various complex structures.It also provides a reliable method for artificial hierarchical self-assembly of functional materials.Due to the orthogonal combination of metal-ligand bonds with other different noncovalent interactions（NCIs）,multiple functional moieties can be easily introduced onto the predesigned metal cages,which provide the possible secondary interactions for hierarchical self-assembly,thus providing a highly efficient strategy for constructing supramolecular complexes with higher-order structures and desired functionalities.In our previous works,anion-coordination-driven assembly（ACDA）strategy has been utilized to construct diverse architectures like two-dimensional（2-D）polygons and three-dimensional（3-D）polyhedra.However,the use of anions as core building blocks for gels remains rare with the fabrication of anion-coordinated self-assemblies into soft materials driven by hydrogen bonds remaining a major challenge.To precisely achieve the targeted functional architectures through hierarchical self-assembly,hydrogen bond donors and acceptors possessing different binding abilities for the specific anion should be rationally devised and combined.Herein,a series of C₂-symmetric anion-binding ligands equipped with ortho-phenylene-bridged bis（urea）and amine or amide ends were designed,which generated A₂L₃ triple helical architectures upon self-assembly with phosphate ions.Hierarchical intermolecular hydrogen bonds among the terminal amine/amide groups and urea moieties resulted in the formation of functional gels.The obtained gels show effective and stable adhesive properties,selective wettability,and conductivity.This thesis is divided into two chapters to introduce the following contents.The first chapter is introduction,which summarizes the molecular self-assembly,briefly introduces the metal-coordination and anion-coordination self-assembled supramolecular structures and the functional materials constructed by hierarchical self-assembly,as well as the aim and significance of this thesis.In the second chapter,four C₂-symmetric bis-bis（urea）ligands(L^NH2,L^Me,L^Pr and L^Hept)ended with aniline,N-phenylacetamide,N-phenylbutyramide and N-phenyloctanamide were designed and synthesized starting from tris（4-aminophenyl）amine,which generated triple helical architectures(H^NH2,H^Me,H^Pr and H^Hept)upon self-assembly with phosphate ions in acetonitrile.Single crystal X-ray diffraction of H^Me showed multiple intermolecular hydrogen bonds between adjacent triple-helical complexes:one is formed between the terminal amide groups and another one between the amide group and a urea moiety.In the tired chapter,four complexes were firstly redissolved in acetonitrile（21.4 m M）,evaporation of a certain amount of solvent to increase the concentration（0.28-0.30 M）resulted in the formation of the corresponding gels(G^NH2,G^Me,G^Pr and G^Hept),respectively.Rheological experiments showed that all of them behave as gels,as indicated by G’values that are always above G’’over the range of frequencies tested.G^Pr exhibits the highest G’value.¹H NMR spectra and high-resolution ESI mass spectra of G^Pr were measured after the rheological experiment,which indicated that a new[A₄L₆^Pr]type phosphate complex had formed.Concentration-dependent ¹H NMR spectra further proved that the[A₄L₆^Pr]type phosphate complex existed at higher concentration.Several substrates with extremely different surficial properties were selected for comparison to investigate the adhesive ability of the gels,including polytetrafluoroethylene（PTFE）,glass,steel,wood and polymethyl methacrylate（PMMA）.All of the adhesives exhibit relatively strong adhesion strengths on wood and PMMA,but show the weakest adhesion effect on the PTFE surface.Here,strong and stable adhesion on wood or PMMA was realized by G^Pr,which can carry a weight of 10 kg.Contact angle test reveal the tunable wettability of the gels when acting as coating materials.Circuit experiment demonstrated the application of the gels as flexible and conductive adhesive materials.