Perylene diimide with huge size substitution both at the imide and bay area position:synthesis and self-assembly behavior

摘要

As aromatic molecules, PDIs have four conjugated benzene rings in the core which could provide strongπ-πinteractions acting as the primary force to drive the self-assembly structure. Usually the coherentπ-πstacking is the basic packing structure in the assembled nanostructures of PDIs. In order to further tune the final self-assembly structure, the two imide and four bay positions can be functionalized together or separately, thus providing extra secondary forces such as static interaction, dipole moment, hydrophilic/hydrophobic interaction to intervene or modulate the coherent π-π interactions in core position. Solvent is crucial for PDI-based derivatives to self-assemble to desired structures, however, major drawback for this kind of materials is their poor solubility, which results in much trouble in synthesizing, purifying, characterizing, and further self-assembling process. In recent years, solubility in common solvents, chemical stability and photochemical properties have been improved by introducing long alkyl chains to the two imide positions. But for self-assembly only using this method just gives one secondary force-hydrophilic/hydrophobic interaction-to the system, in order to further tune the self-assembly process, also to make PDI based materials environmental friendly, water soluble, some other functional groups were introduced to incorporate with alkyl chain tails as modification units. This thesis focuses on the synthesis, and self-assembly behavior of bulky imide and bay area substitution. The three major compounds include N,N’ -di(2-ethylhexyl)-1,7-dibromoperylene-3,4,9,10-tetracarboxylic acid bisimide, bay area POSS substituted, and phenol. The synthesis, characterization and investigation of the compounds, in which bromine was substituted with POSS and phenol respectively, were done. Characterization in solution (1H NMR spectroscopy) and FT-IR spectroscopy proves the identity of the compounds under investigation. The UV-Vis spectra and fluorescence spectra in single solvent and bi-solvent were used to study self-assembly behavior, Photolumiscence results as expected showed mirror images of the absorption with all the three main peaks appearing.
　　Due to poor solubility and ability to self-assemble of PDI, normally associated withπ-πinteractions, makes it difficult to apply in photovoltaic cells. To achieve good solubility and optoelectric properties, we functionalized the imide position with branched ethylhexylamine because it will hinder theπ-πinteractions by interfering with the planarity and increasing theπ-πdistance thus making it weak. Due to its bulkiness, POSS, incorporation in organic chromophores plays a major role in reduction of aggregation, leading to better properties which are persistent in the solid state. Three PDI-based derivatives, ethylhexylamine, POSS and phenol were successfully synthesized via a systematic and convenient method, getting rid of the low solubility of perylene. Chapter one, provides an introduction to current research on solar cells with a focus on organic polymer and dye-sensitized cells. The detailed mechanisms of introducing functional groups and various ways of improving it solubility and other optoelectronic properties are outlined. In addition, an overview of the progress over the last decade in research on polymer photovoltaics is given. Finally, the future prospects for achieving high efficiency devices are described. Chapter two, the synthesis of novel n-type polymers based on PDI monomers, N,N’ -di(2-ethylhexyl)-1,7-dibromoperylene-3,4,9,10-tetracarboxylic acid bisimide, is described. With appropriate substitution on imide position, PDIs can be made soluble in common organic solvents such as chloroform and toluene. These materials have exceptionally low-lying LUMOs and possess good fluorescence properties. Photolumiscence results of PDI in the afore mentioned solvents as expected showed mirror images of the absorption with all the three main peaks appearing. PDIs functionalized in the bay positions are typically accessed by dibrominating perylene dianhydride, bromination is also described. Chapter three, PDIs functionalized in the bay positions are typically accessed by dibrominating perylene dianhydride, this chapter details the substitution of bromine with POSS and phenol, with POSS aimed to improve and fine tune the chemical and physical properties of chromophores in addition to impacting on their mechanical properties on the other hand phenol substitution leads to twisting hence reducing the π-π stacking, leading to improved solubility. The success of synthesis was confirmed with HNMR.
　　Chapter four presents the conclusions of the research contained within this thesis and examines possible avenues of further research.

目录

声明

CHAPTER ONE

1.1 Literature Review

1.2.0 Perylene Diimides (PDIs)

1.3.0 Substitution in the Bay Positions

1.4.0 Physical Properties of PDIs

1.5.0 2-ehtylhexylamine nanoparticle as an N-imide substituent

Reference

CHAPTER TWO Synthesis, Characterization and self-assembly behavior of Amide substituted Perylene Diimide

2.1 Introduction

2.2 Experimental section

2.3 Results and discussion

2.4 Conclusion

Reference

CHAPTER THREE Synthesis of new derivatives of PDIs by the bay-substitution of bromine with Polyhedral oligomeric silsesquioxane

3.1 Introduction

3.2 Experimental

3.3 Results and discussion

3.4 Conclusions

Reference

CHAPTER FOUR

4.1 Conclusion and limitations of the project

4.2 Limitations of this research work

致谢