Preparation of Polystyrene-Polyimide Particles by Dispersion Polymerization of Styrene Using Poly(amic acid) as a Stabilizer

Dispersion polymerization of styrene (S) and a cationic comonomer, 4-(vinylbenzyl)trimethylammonium chloride (VBA) was conducted in alkaline aqueous ethanol using various aromatic poly(amic acid)s (PAA) as stabilizers. The monodisperse particles were obtained in high yield using the optimum composition of solvent mixture depending on the PAA structure. By using a cationic comonomer (VBA), PAA was incorporated quantitatively into the particles. On the other hand, using cationic methacrylates as a comonomer, PAA was not incorporated effectively. The imidization of PAA on the particles proceeded with acetic anhydride and 4-(dimethylamino)pyridine to form PS-polyimide (PS-PI) particles. The PS-PI particles were maintained in spherical shape by the thermal treatment up to 240 °C. PI hollow particles were also obtained by washing PS-PI particles with toluene.