Synthesis and Characterization of Novel pi-Conjugated Small Molecules and Polymers with Hydrogen Bonding & Preparation of 2D Single Crystals for Organic Field-Effect Transistors

Two pi-conjugated polymers containing isoindigo or 3,3-(ethane-1, 2 diylidene)bis(indolin-2-one) (EBI) units with latent hydrogen-bonding on the main chain were synthesized and characterized. The designed polymers use thermal liable t-Boc groups as side chains on the backbone and can be easily dissolved in common organic solvent. Further thermal treatment of the polymers at around 180 oC can convert the polymers into strong hydrogen-bonded materials. The effect of formation of intermolecular hydrogen bonding networks on the polymer film properties including the UV/Vis absorption and electrochemical properties are studied. In the second part of this work, 2D organic single crystals of three conjugated small molecules, di-tert-butyl 1,4-dioxo-3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-2,5(1H,4H)-dicarboxylate (DPPBoc), isoindigo, and cyclized DPP were successfully prepared by either solution epitaxial growth, mechanical exfoliation, or physical vapor deposition methods for organic field-effect transistor (OFET) applications. A thickness that less than 100 nm can be achieved for the obtained 2D crystals.