Highly Heat-Resistant Poly(bismaleimide-co-styrene) Microspheres Bearing Maleimide Functional Groups by Self-Stabilized Precipitation Polymerization

Herein, we report the synthesis of novel heat-resistant microspheres by self-stabilized precipitation copolymerization of styrene (St) and 2,2′-bis[4-(4-maleimidophenoxy)phenyl]propane (BMIP) in an mN-methyl pyrrolidone (NMP)/isopentyl acetate (IPA) mixed solvent. The effects of the solvent composition, monomer feed ratio, monomer, and initiator concentration on the size and morphology of the resultant poly(BMIP-co-St) microspheres were investigated in detail. Monodisperse, highly cross-linked poly(BMIP-co-St) microspheres with number-average diameters ranging from 2.23 to 1.28 μm were successfully obtained at a 1/2 molar ratio of [BMIP]/[St] in NMP/IPA (2/13, v/v). Due to the presence of a rigid imide ring and a highly cross-linked structure, the poly(BMIP-co-St) microspheres exhibited excellent thermal stability with an initial decomposition temperature up to 440 °C and a 30% char residue rate at 750 °C. Additionally, there were some unreacted maleimide groups on the surface of poly(BMIP-co-St) microspheres for further chemical modification, making the poly(BMIP-co-St) microspheres highly interesting as advanced functional materials.