Design and Synthesis of Aryl Amphiphiles to Control the Growth of π-Conjugated Microcrystals along the π-Stack Direction
Jones, Dorothy Keely
Photonic integrated circuits (PICs) are capable of overcoming the numerous limitations facing traditional integrated circuits, such as the heat generated by the fast movement of electrons and the size limitations. However, PICs cannot be a viable alternative to traditional integrated circuits without miniaturization. π-conjugated organic microcrystals (PiMC) are the most promising solution to miniaturize PICs due to their strong active photonic behavior. PiMCs are also generally attractive due to their tunable electronic and optical properties. Most PiMCs have shape-dependent optoelectronic properties since their shape and crystal packing motif has a large influence over the directionality and intensity of light guided through the PiMC. Thus, the shape of a microcrystal governs the PiCM’s optoelectronic properties and thus its applications.Despite the need to be able to control the shape of a PiMC to achieve desired properties, such control has not yet been fully realized. Polymer stabilizers have shown some success in controlling the shape of PiMCs but their structural complexity makes it difficult to understand their mechanism of action. Alkyl amphiphiles are also commonly used but have limited effect on the final PiMC shape because they are limited to weak CH-π or van der Waals interactions between the alkyl hydrophobe and the microcrystal facet. Aryl amphiphiles are a better candidate for use as morphology directors (MoDs) can exhibit π-π or CH-π interactions with the PiMC crystal facets and thus have a greater impact on the PiMC shape. Additionally, it is possible to synthesize MoDs with a variety of different hydrophobe structures which will result in greater control of the PiMC shape. Aryl amphiphiles can also be useful for other applications where alkyl amphiphiles fall short, such as in the dispersion of graphitic materials. In this work, seven novel aryl amphiphiles MoDs were designed, synthesized and characterized. These MoDs were used to effectively control the morphology of 9,10- diphenylanthracene and perylene PiMCs. The optical properties of the perylene PiMCs were also studied, and the PiMCs were found to have shape-dependent optical properties, and demonstrated the first reported example of waveguiding along an edge-to-edge packing direction of a PiMC. Additionally, the MoDs were used to effectively disperse graphene nanoplatelets (GNPs) in solution.
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