Highly Crystalline, Nanostructured Polyimide Microparticles via Green and Tunable Solvothermal Polymerization

Abstract

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.