Baumgarten, B.; Bojdys, M. J.; Unterlass,* M. M. Polymer Chemistry 2014, 5, 3771-3776.
Inspired by geological ore formation processes, we apply one-step hydrothermal (HT) polymerization to the toughest existing high-performance polymer, poly(p-phenyl pyromellitimide) (PPPI). We obtain highly-ordered and fully imidized PPPIs as crystalline flakes and flowers on the micrometer scale. In contrast to classical 2-step procedures that require long reaction times and toxic solvents and catalysts, HT polymerization allows for full conversion in only 1 h at 200 °C, in nothing but hot water. Investigation of the crystal growth mechanism via scanning electron microscopy (SEM) suggests that PPPI aggregates form via a dissolution-polymerization-crystallization process, which is uniquely facilitated by the reaction conditions in the HT regime. A conventionally prefabricated polyimide did not recrystallize hydrothermally, indicating that the HT polymerization and crystallization occur simultaneously. The obtained material shows excellent crystallinity and remarkable thermal stability (600 °C under N2) that stems from a combination of a strong, covalent polymer backbone and interchain hydrogen-bonding.
Baumgarten, B.; Bojdys, M. J.; Unterlass,* M. M. Polymer Chemistry 2014, 5, 3771-3776 – Reproduced by permission of The Royal Society of Chemistry