Micro-flowers of poly(p-phenylene pyromelliteimide) crystals

Morphology control of poly(p-phenylene pyromelliteimide) (PPPI) crystals was examined using reaction-induced crystallization of oligomers during solution polymerization of self-polymerizable N-(4′-aminophenyl)-3-carboxyl-4-alkoxycarbonylphthalimide. Micro-flowers of the PPPI needle-like crystals were formed in which the needle-like crystals grew radially from the center part as petals. The molecules aligned regularly along the long axis of the needle-like crystal. The structure of alkoxy group in the monomer and the monomer concentration influenced the size of the needle-like crystals, and their average length and width were changeable from 640 nm to 1.69 μm and from 110 nm to 210 nm, respectively. The average thickness was 20 nm. The obtained micro-flowers possessed high crystallinity and exhibited excellent thermal stability.