Fabrication And Aggregation Structure Control Of The Low-dimensional Supramolecular Functional Materials Based On Perylene Bisimide Blocks

Compared with one-dimensional (1D) single-component organic materials,well-defined1D multicomponent supramolecular structures based on smallπ-conjugated molecules have attracted increasing attention because of theirinteresting optical and electronic properties and great potential applications inintegrated optoelectronic devices. Among several available strategies for thecontrolled formation of multicomponent assemblies, multiple hydrogen bondinginteraction is the most beneficial noncovalent glue to create highly organizedheterocomplexes due to their high selectivity and directionality. However, mosthydrogen-bonded assemblies reported to date fail to display well-ordered1D shapesbecause it is difficult to precisely control the balance of complicated intermolecularinteractions including π-π stacking, hydrogen bonding, van der Waals, hydrophobicinteractions and steric constraints. Therefore, by means of hydrogen bondinginteractions, assembling functional organic moleculars containing hydrogen bondingunits into1D multicomponent mesoscopic superstructures with highly ordered π-πstacking molecular arrangement remains an enormous challenge in the viewpoint ofsupramolecualr chemistry. In the thesis, supramolecular assembling unit were firstlydesigned reasonably and constructed into well-defined aggregation structures basedon Perylene Bisimide with excellent optical and electronic properties. Meanwhile, weinvestigate the structure and performance of these materials, the mechanism ofself-assembling, and the factors which affect the process of self-assembly in depth.Three new bis-melamine compounds, namely bisM-6, bisM-12and bisM-18,were successfully synthesized, which featuring symmetrical dimeric melaminehydrogen bonding moieties tethered by piperazine linker. These compounds weredesigned with the idea to form binary supramolecular complex with PBI as themelamine unit is well-known for its triple hydrogen bonding with ditopic imidebuilding blockes of PBI molecular. These structure of these molecules wascharacterized by1HNMR,and FT-IR.Two well-defined1D mesoscopic supramolecualr structures have beenreadily prepared on a large scale by hierarchically assembling from PBI bisM-6and PBI supramolecular systems in solution. FE-SEM images showed PBI bisM-6rods have very smooth surfaces have a length of10μm-40μm and a widthof about1.3μm, in contrast, PBI rods display the characteristic of gear-like surfaces. XRD indicated a hexagonal columnar organized with an intercolumnarspacing ah e xof22.86for the complex PBI bisM rods, moreover, the PBI bisM-6is more likely to exhibit excellent optoelectronic performance than PBI,as thefomer has much more highly organized structure. OPM images revealed theanisotropic optical properties of both1D assemblies, which are expected to beuseful building blocks to control polarization of light in future miniaturizedphotonics. Furthermore, the growth processes of the two assemblies as well assecondary bonding interactions were fully characterized by OPM, UV-Vis,1HNMR, and FT-IR. The results revealed the formation of hydrogen-bondingbetween PBI and bisM-6, surprisingly, the addition of bisM leads to a dramatictransformation in packing conformation of PBI melecules from J-type to face-facestacked H-type molecular arrangement. As aggregate structure of the molecularplays an mportant role in the performance of its corresponding material (forexample, H-type aggregates often have a higher carrier mobility than the J-typecounterparts), therefore the phenomenon of structure change in aggregateswill have important significance to the construction of functional materials, whichis also one of the biggest highlights in this dissertation. In addition, theself-assembling process of the rods, which is largely proposed based on experimentresults, is mainly consists of two steps: the columnar phase is formed by orderedπ-π stacking firstly, and then crystallization of the columnar phase results in theformation of1D rods. Meanwhile, the spontaneous characteristic of suchself-assembly process was discussed on the basis of gibbs free energy, and it wasfound that the combination of hydrogen bonding and ordered π-π stacking ofperylene unit are the main driving forces for the spontaneity of the self-assemblyprocess,leading to the ordered aggregate structureThe aggregate structures of PBI bisM-12and PBI bisM-18have also beenconstructed by a similar self-assembly method as PBI bisM-6. FE-SEM imagesshowed that the structure of PBI bisM-12rods was similar to PBI bisM-6, but notas regular as the later, and even no discreet rod-like structure was obtained as forP BI b i s M-18. X R D c ould n ot r e s o l v e the s pe ci fi c cr y st a l str u ct ure o f bothaggreges,but indicated that the PBI bisM-12exhibited much more highlyorganized structure than that of the PBI-18,and OPM images revealed the sameanisotropic optical properties of PBI bisM-12rods. Furthermore, the growthprocesses of the two assemblies as well as secondary bonding interactions werefully characterized by OPM, UV-Vis,1HNMR, and FT-IR. The results reveal that hydrogen bonding and π-π stacking of perylene unit are still the maindriving forces for the spontaneous processes in PBI bisM-12and PBI bisM-18as well as PBI bisM-6, and it was found that the difference in these aggregationswas mainly due to the long alkyl chain of bisM,which will reduce the π-π stackingof perylene unit,leading to ill-defined one-dimensional structure. In addition, a "Thermal-Reversible" supramolecular gel of PBI bisM-12was formed by using asimple heating-cooling procedure, which provide us a new idea on the formationof functional materials based on supramolecular gels.The aggregates of two compounds, namely N-PBI and PBI, have also beenconstructed in solution by four kinds of supramolecular self-assembly methods. It wasfound that these aggregate structures were totally unique when different moleculesassembled in different conditions. In which, well-defined and very large belt-likeaggregates, which have the length of0.1-0.3mm, width of15μm and height of3μm,was obtained when assembling N-PBI by a phase transfer method. These resultsshowed that both the molecular structure and the self-assembly method play animportant role in supramolecular self-assembling and the corresponding aggregatestructure. These results not only provide a new method and approach to constructlow-dimensional supramolecular functional materials based on perylene imide asbuilding blocks, but also make a available to deeply understanding the relatedmechanism of supramolecular assembling and the corresponding aggregate structure.