In the past few decades, conjugated polymers have been discovered and later recognized by a Noble Prize in 2000. Polythiophene with low band gap of 1.9 eV is one of the most studied conjugated polymers. However, polythiophene is a p-type polymer, and there is a need to develop n-type low band gap polymers to achieve unique advantages over traditional metallic materials and fullerene such as light-weight and tunable photoconductivity. Here we show that the dimensional geometry in linear-, tri- and tetra-perylene-based polyimides significantly affects the conductivity and the possible hybridization with 2D-molybdenum disulfide in both solvothermal and hydrothermal synthesis. The hydrothermal synthesis of linear and hyperbranched polyimides in only water without a catalyst or organic solvents was examined resulting in unique properties such as the crystals with regular repeating array. The thermal stability of the polyimides was examined demonstrating high decomposition temperatures as observed for Tetra-PPI at (899 °C) with only 29.5 % weight loss. Furthermore, morphologies of the linear and hyperbranched polyimides reflected fibril- or flake-like structures. The presence of MoS<sub>2</sub> promotes not only the conductivity but also the thermal properties and the 2D polymerizations and growth noting that the dispersions stability of various nanocomposite samples were stable &gt; 8 months in water. The calculated band gap of linear PPI/MoS<sub>2</sub> resulted in a low band gap of 1.25 eV, and almost forty-degree increase in the glass transition of Tri-PPI. Therefore, hyperbranched structures can be a far superior matrix for nanocomposites. We anticipate this study to be a starting point for more n-type polymers and nanocomposites due to the possible correlation between the design and the tunable properties based on the perylene core substitutions, the nature of the connected monomers and the filler.

Linear and hyperbranched perylene based polyimides: Polymerization and hybridization with molybdenum disulfide nanosheets

ACS Fall 2021

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