Highly fused, fully conjugated aromatic compounds are interesting candidates for organic electronics. With higher crystallinity their electronic properties improve. It is shown here that the crystallization of three archetypes of such molecules-pentacenetetrone, indigo, and perinone-can be achieved hydrothermally. Given their molecular structure, this is a truly startling finding. In addition, it is demonstrated that perinone can also be synthesized in solely high-temperature water from the starting compounds naphthalene bisanhydride and o-phenylene diamine without the need for co-solvents or catalysts. The transformation can be drastically accelerated by the application of microwave irradiation. This is the first report on the hydrothermal generation of two fused heterocycles.

Hydrothermal polymerization (HTP) is a benign and inherently green synthetic approach to synthesize highly crystalline polyimides (PIs) in nothing but high‐temperature water (HTW). In a typical HTP experiment, highly crystalline PI microparticles of sheet‐like as well as flower‐like morphology are obtained. Within this contribution, the effect of four additives (PEG400, PEG8000, P123, CTAB) on the crystallinity and morphology of the PI poly(p‐phenylene pyromellitimide) is investigated. From the experiments performed, it becomes evident that the type as well as the concentration of additive heavily influences morphology. However, even the highest tested concentration of additive (67 g L−1 of PEG8000) does not lead to a change in average crystallinity, as determined from powder X‐ray diffraction. Hence, this approach provides a straightforward method to intentionally tune PI particle morphology without losing the outstanding materials properties generated by the high crystallinity obtained via HTP. Additionally, a hypothesis regarding the poly(ethylene glycol)‐induced morphology alteration is presented.

Various polyimides and polyamides have recently been prepared via hydrothermal synthesis in nothing but H2O under high‐pressure and high‐temperature conditions. However, none of the prepared polymers feature a truly conjugated polymer backbone. Here, we report on an expansion of the synthetic scope of this straightforward and inherently environmentally friendly polymerization technique to the generation of conjugated polymers. Selected representatives of two different polymer classes, pyrrone polymers and polybenzimidazoles, were generated hydrothermally. We present a mechanistic discussion of the polymer formation process as well as an electrochemical characterization of the most promising product.

Herewith, we report a straightforward, experimentally simple, and environmentally benign synthetic strategy toward cyclocondensation polymers. Using a fully aromatic polyimide as model system, we demonstrate that products of extraordinary crystallinity can be generated in various protic, polar solvents (ethanol, iso-propyl alcohol, and glycerine) as well as in their mixtures with H2O via solvothermal polymerization. Depending on the type of solvent and the employed solvent composition, respectively, several physicochemical solvent properties (density, viscosity, polarity, and ionic product) can be intentionally adjusted to generate a plethora of morphologically different microparticlespartly with highly ordered structures down to the nanorangewhile maintaining full crystallinity. The method developed here is a highly valuable addition to the to date rather limited number of synthetic approaches toward high-performance polyimides and, as we believe, for cyclocondensation polymers in general.

Poly(p-phenylene vinylene)s (PPVs) have been studied for decades, but new applications like in bioimaging keep emerging and even simple structural variations are still waiting to be explored, as we highlight by this work.