Exerting Additive-Assisted Morphological Control during Hydrothermal Polymerization

Abstract

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.