Study On Self-assembly And Properties Of Perylene Bisimide Regulated By Organic Acids

The high surface area and quantum effect endow the nanomaterials with unique properties,making them promising in the fields of electricity,magnetism,optics,sensors and catalysis.Currently,the synthesis of functional nanomaterials mainly uses self-assembly;?-conjugated system have attracted extensive attention due to its designable molecular structure and excellent photoelectric performance.As an excellent?-conjugated system,perylene bisimide derivatives(PBI)have strong?-?stacking interactions that allow them to self-assemble into nanomaterials of various sizes and morphologies,and morphology and structure of the aggregate determine its photoelectric performance.So,it is of great significance for the current PBI research to obtain aggregates with different morphologies and properties by changing the molecular structure and assembly conditions to adjust the driving forces in the self-assembly.Therefore,two perylene bisimide derivatives containing tertiary amines were synthesized and self-assembled in different assembly systems.The effects of molecular structure and assembly conditions on morphology and performance of PBI aggregates were analyzed.The research results are as follows:1.Two perylene bisimide derivatives PBI-R(PBI-1 and PBI-2)containing tertiary amines were synthesized by selecting appropriate amine compounds and their molecular structures were determined by NMR and IR spectroscopy.2.The fast solvent diffusion method was used to self-assemble PBI-1 and PBI-2molecules in THF/water assembly system containing different organic acids.The effects of molecular structure and organic acids on the morphology and properties of aggregates was discussed.The results showed that the color of PBI-1 aggregates changed from red to blue in seven organic acid,while the color of PBI-2 aggregates remained red.Two aggregates are J-type aggregates and still have fluorescence,the red-shift of the maximum absorption peak of PBI-2 aggregates is smaller than that of PBI-1 aggregates,and the Stokes shift of PBI-2 aggregates(about 60nm)larger than PBI-1 aggregates(about 25nm),indicating that intermolecular?-?interaction of PBI-2 molecules during aggregation is stronger than PBI-1.PBI-1 molecules can form fibers in seven organic acid,but fibers formed in polyacid systems are shorter than those in monobasic acid,indicated the degree of protonation and molecular structure of organic acids will affect the aggregation of PBI-1 molecules.As r(the concentration ratio of H~+and tertiary amine groups)increases and p Ka decreases,the red-shift of the maximum absorption peak increases,indicated that the charge repulsion interaction is enhanced and the?-?interaction is weakened.XRD confirmed the difference in the self-assembly of PBI-1 molecules in different organic acid.After heating at 120?for 2h,the maximum absorption peak of the PBI-1 aggregate formed in the monobasic acid was unchanged,while that of the polyacid is blue-shifted,indicated that the PBI-1 aggregates have sensitivity to temperature.After ammonia treatment,the maximum absorption peak of PBI-1 aggregates shifted blue,and the blue shift gradually increased with time and temperature,indicated that PBI-1aggregates were sensitive to ammonia.And the possible PBI-1stacking in different organic acid systems is described.3.The fast solvent diffusion method was used to self-assemble PBI-1 molecules in five solvents containing trichloroacetic acid,that is,chloroform/methanol,THF/ethanol,chloroform/n-hexane,THF/n-hexane and THF/water.Analyze the morphology and photophysical properties of aggregates,and explore suitable system.The results show that PBI-1 aggregates with regular morphology cannot be formed in THF/ethanol and chloroform/n-hexane systems;the aggregates formed are mostly disordered and fine amorphous grains in the THF/n-hexane system;In the chloroform/methanol and THF/water assembly system,PBI-1 molecules form regular blue aggregate fibers within a r range,and the number and length of fibers is to increase and then decrease.The r of the aggregates turning blue in the five systems is:r THF/ethanol>r chloroform/n-hexane?r THF/water>r THF/n-hexane?r chloroform/methanol.The PBI-1aggregates are J-type aggregates in the five systems.4.The phase transfer was used to self-assemble PBI-1 molecules inchloroform/methanolcontaining glutaric acid,and the morphology and photophysical properties of the aggregates were characterized.The results show that PBI-1 molecules have been aggregated after 2 hours,and the morphology and number of aggregates have basically stabilized after 2 days.The addition of glutaric acid slowed down the self-assembly and changed the morphology of the PBI-1 aggregates from short rods to long fibers.With the increase of r and time,the length and number of fibers increased,indicating glutaric acid facilitates the formation of fibrous aggregates.At the same time,J-type aggregates are formed in the system.