Preparation of poly(p-phenylenepyromelliteimide) microspheres with rugged surfaces using crystallization during isothermal polymerization

Preparation of discrete PPPI microspheres was examined using the crystallization of oligomers during isothermal polymerization of PMDA and p-phenylene diisocyanate, and that of pyromellitic dithioanhydride and PPDA in poor solvents. In contrast to PPPI microspheres with smooth surfaces that were previously prepared by phase-separation during the polymerization of PPDA and PMDA, the microspheres obtained here consisted of flake-like lamellae with rugged surfaces. The diameters of the microspheres ranged from 0.5 to 6.7 μm. They exhibited excellent thermal stability depending on the monomers. These results provide a new preparative procedure of the PPPI microsphere with a rugged surface. (figure prested)