Synthesis And Characterization Of Amphiphilic Molecules Of Pyrene

Self-assembled nanoscale or micron-scale structures are of great research interest for materials science,biology and medicine.It is very interesting to go from the synthesis of small molecules to the beginning of the construction of complex and ordered self-assemblies.In order to make self-assembled materials useful for specific purposes,special stimulatory reactions are often introduced to modulate the nanostructure.Supramolecular self-assembly is the binding together of molecules through intermolecular(non-covalent)interactions to form assemblies with specific structure and shape,stable properties and certain functions.Nowadays,many scientists use the knowledge of supramolecular self-assembly to solve many scientific problems,and it can be said that supramolecular chemistry is a sunrise discipline with great potential for use and application.The design and development of novel supramolecular two-dimensional self-assembled nanomaterials has been a hot topic of supramolecular chemistry research,but so far few supramolecular main body nanomaterials with pyrene as the basic building block have been reported,so in this paper,we chose to synthesize amphiphilic molecules by connecting single or double-chain dendritic alkoxy chains at the end of pyrene as the basic building block.And with these two different amphiphilic molecules,the following were investigated.1.Synthesis and properties of dendritic alkoxy linked single chain amphiphilic moleculesIn the first part of our work,we designed and synthesized single-chain amphiphiles based on pyrene,which consist of an aromatic end containing a pyrene group and a hydrophilic alkoxy chain end attached at the aromatic end.The morphological analysis by scanning electron microscopy and transmission electron microscopy also revealed that the single-chain amphiphiles spontaneously assembled into monolayers of lamellar structures in two different solvents.The occurrence of the aggregation behavior could be confirmed by the decrease of the UV maximum absorbance and the quenching of the fluorescence.Moreover,during the dynamic heating self-assembly process,we speculate that the dendritic chain molecules located in the aromatic segment linkage did not undergo dehydration due to partial hydrogen bond breakage upon heating,thus increasing the spatial site resistance and thus affecting the alignment of the aromatic chain ends.As a result,the light absorption intensity can still be restored to 25°C after heating and cooling.It is shown that our designed single-chain aromatic amphiphiles based on pyrene can spontaneously assemble into tightly arranged two-dimensional nanosheets in both different solutions,and the formed assemblies have some thermal stability.2.Synthesis and properties of double chain amphiphilic molecules with dendrimer alkoxy linkagesNanostructures can exhibit different nano-properties depending on the building blocks and external stimuli,e.g.,nanosize,histomorphology,stability,etc.Inspired by this,we designed and synthesized in this section a double-chain amphiphilic molecule based on pyrene.The amphiphilic molecule consists of a hydrophobic aromatic end based on pyrene,and two hydrophilic ends of dendritic alkoxy-linked branches.The morphology of the amphiphiles in pure aqueous solution or(THF-H2O)mixed solution was investigated by scanning electron microscopy and transmission electron microscopy,and it was found that the amphiphiles spontaneously assembled into parallel-arranged monolayers in both pure aqueous solution and mixed solution.interaction and aggregation.During the dynamic heating self-assembly process,we speculate that the single chain ends connected at the aromatic end will slip in the same direction to reduce the site resistance and prevent the parallel-aligned chain molecules from becoming randomly aligned,so the assemblies can still recover the UV absorption intensity at 25°C after cooling down after heating at 70°C.The heating does not destroy the arrangement of the amphiphilic molecules.In conclusion,we have successfully designed and synthesized single-or doublechain amphiphiles and demonstrated that they can spontaneously self-assemble in pure aqueous solution or(THF-H2O)mixed solution to form monolayer lamellar structures with certain thermal stability.Moreover,the toxicity of the substrate pyrene was reduced by the modification to increase the biocompatibility,which is expected to be widely used in biomedical field and in the field of green chemistry research.