Photocontrolled Self-assembly Of Coumarin-perylene Diimide And Its Directed Alignment Of Graphene

Perylene diimide(PDI)derivatives have excellent optical,thermal,and electrical properties,and the strong π-π interaction between molecules makes them widely used in the construction of superior supramolecular aggregates.In this paper,two kinds of light-responsive perylene diimide derivatives with different π-π stacked types were synthesized by introducing coumarin groups with photodimerization properties at the amide site of p-perylene diimide.Under the photodimerization of the coumarin group,the two perylene diimide derivatives realize the morphology control of supramolecular aggregates.On this basis,graphene photoresponsive materials were prepared by non-covalent bonding of graphene with one of the perylene diimide derivatives.Illumination can also significantly change the electrical conductivity and capacitance of materials,which provides an important reference value for graphene-based photosensitive smart materials and the enhancement of the directional arrangement of graphene.1.Designed and synthesized two photo-responsive coumarin-perylene diimide derivatives(PDI-A and PDI-B)with different imide steric hindrances,ultraviolet-visible absorption spectra show that the two materials have good reversible light responsiveness.2.The self-assembled aggregates of PDI-A and PDI-B were prepared by rapid diffusion method and phase transfer method,and the self-assembly stacking mode and morphology of the two molecules before and after the photodimerization reaction in the corresponding poor solvent were studied by ultraviolet-visible absorption spectroscopy,fluorescence emission spectroscopy and scanning electron microscope.The self-assembly method has a great influence on the size of the self-assembled aggregates,and the aggregates prepared by the phase transfer method have a higher aspect ratio and larger size.Ultraviolet and fluorescence spectra show that the selfassembly behaviors of PDI-A and PDI-B are J-type and H-type,respectively.Before photodimerization of PDI-A molecules,one-dimensional nanoribbons or interwoven nanowires are formed due to different assembly methods,and short bundled rod-like structures are formed after photodimerization.PDI-B molecules form round flakes and rectangular flakes before photodimerization.After photodimerization,they form multilayer stacked aggregates.When the molecules are depolymerized by 254 nm ultraviolet light,they form rice grains and popcorn-like aggregates.3.Using the π-π stacking interaction between the PDI-B molecule and graphene,the non-covalent bond modification of graphene by coumarin group was realized,and the PDI-G hybrid was prepared.Under 365 nm UV irradiation,the compound can accumulate and sink.The results of spectral and morphology investigation showed that the photodimerization of coumarin realized the stack of graphene sheets.The originally disorderly arranged materials were stacked into an ordered structure,and the graphene was reconstructed into a layered structure,which process was gradually carried out with the ultraviolet light.4.The electrochemical performance test of the material shows that ultraviolet light can significantly change the capacitance and conductivity of the PDI-G hybrid material.After 3200 s ultraviolet light irradiation,the capacitance of the material gradually decreased from 46.5F/g to 7.8F/g,and this change was caused by the gradual accumulation of lamellae.This kind of photo-responsive graphene self-assembly behavior has good applications in the construction of smart materials,high-performance materials,and other fields.