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M. J. Taublaender, M. M. Unterlass:
"Hydrothermal Polymerization - A New Strategy for High-Performance Polymers";
Poster: Japan Polyimide Conference 2018, Tokyo, Japan; 2018-10-13.

Introduction
We have recently reported a novel, environmentally benign synthetic approach for generating advanced organic materials: Hydrothermal Polymerization (HTP). HTP only requires H₂O under high-temperature and high-pressure conditions as the sole reaction medium and catalyst. Among others, this new method
allows for preparing various polyimides (PIs).[1] In addition to that, other high-performance polymers such as polybenzimidazoles,[2] and polyperinones,[3] can be synthesized hydrothermally. For all of these materials, certain properties such as mechanical, chemical and thermal stability profit from their
preparation under hydrothermal (HT) conditions.

Experimental
For synthesizing PIs (Fig. 1 A), the starting compounds - an aromatic dianhydride and an aromatic diamine - are dispersed in solely H₂O and heated to elevated temperatures (> 180 °C) in a closed vessel aka autoclave. After the reaction time tR, the autoclave is cooled back to room temperature and the
synthesized PI powder can be isolated via filtration.

Results & Discussion
Under the arising high-temperature and high-pressure conditions in the autoclave, H₂O becomes an ideal reaction medium for polycondensations. Interestingly, HTP generates PIs of full crystallinity with unique morphologies (Fig. 1B) that can moreover be intentionally altered by the application of additives.[4] The feature of full crystallinity is extremely promising: It enhances chemical, mechanical and thermal stability in these polymers. Hence, the properties that are most important to PIs´ applications benefit from their preparation via HTP.
References

[1] B. Baumgartner, M. J. Bojdys, M. M. Unterlass, Polym. Chem. 2014, 5, 3771.
[2] M. J. Taublaender, S. Thiele and M. M. Unterlass, AT A 374/2017, submitted September 20th 2017.
[3] M. J. Taublaender, S. Thiele and M. M. Unterlass, AT A 373/2017, submitted September 20th 2017.
[4] M. J. Taublaender, M. Reiter, M. M. Unterlass, Macromol. Chem. Phys. 2017, 219(3), 1700397.