Design, Synthesis And Aggregation Study Of Perylene Diimide Derivatives With High Solubstituentsility

Perylene diimide is a typical n-type organic semiconductor material with excellentthermal stability and unique optical activity and photochemical properties, on account ofwhich its self-assembled aggregates have a wide range potential applications in organicsolar cells, organic electroluminescent devices, organic field-effect transistors and liquidcrystal field. Therefore, design and synthesis of a new-style perylene diimide derivativemolecule with high solubility, and investigation into photoelectric properties ofself-assembly aggregation structure have already become a hot topic in the field ofscientific community.In this study, a novel series of perylene diimide derivatives: N, N'-bis-iso-octyl-3,4;9,10-perylene four carboxy diimide (BIPI) and N-(1-iso-octyl)-N'-(4-cholesteric)-3,4;9,10-perylene four carboxy diimide (NCPI) were synthesized and characterized by FT-IR,~1H NMR. The thermal stability was tested by DSC; besides, their aggregation structureswere studied by different testing methods incluing UV-vis absorption spectroscopy,polarizing microscope, X-ray and field emission scanning electron microscope (SEM).BIPI and NCPI have good thermal stability, and BIPI could be observed visiblediscotic liquid crystal phase texture in polarized light. Confirmed by X-ray analysis, themolecules have a high degree of crystallinity. Because of the steric effects of substituentsand the weakened intermolecular π-π interaction force, the distance of BIPI and NCPIbetween two perylene core planes was larger than the unsubstituted perylene imide's.Crystals of BIPI and NCPI with different sizes and topographies were grown bycasting and saturated solution vapor diffusion methods, and observed by polarizingmicroscope. The dominant factors affecting the crystal sizes and morphologies have beendiscussed incluing different molecular structures, different solvents, differentconcentration and different grown methods. The results indicate that the largerconcentration, the better the solubility, and the easier the crystal growth due to theimproved accumulation capacity of perylene derivatives. In addition, compared with NCPI,BIPI is easier to get a larger size and more neat crystals.The aggregation structures of BIPI and NCPI in different solutions, different concentrations and different ratios of water-tetrahydrofuran solution were investigated byUV-visible absorption spectra. The results show that BIPI and NCPI in good solventshowed a single molecule distribution and aggregated in poor solvent; In different ratios ofwater-tetrahydrofuran solution, BIPI and NCPI were self-assembled into nanoparticleaggregates, respectively, and showed different morphology such as columnar, sphericaland flakes which have sizes from100nm to500nm; With the water content increasing, theabsorption peaks of BIPI and NCPI appeared obvious blue shift and red shift. Theaggregates showed an alignment property of J-aggregates and H-aggregates, and themolecular in aggregates showed a spiral staggered arrangement.