Culturing and characterization of two types of single crystals of polyhedral oligomeric octaphenylsilsesquioxane

Polyhedral oligomeric octaphenylsilsesquioxane (OPS) has been widely concerned for improving the thermal stability and flame retardancy of polymers. The crystal forms of OPS have a substantial influence on the morphologies and properties of their microparticles. Therefore, it is crucial to study the properties and culture methods of different OPS single crystals. Most of the reported OPS crystals are solvent-containing. The research on solvent-free OPS single crystals cultured by recrystallization has not been reported. In this work, solvent-free monoclinic single crystals and solvent-containing tetragonal single crystals were cultured by recrystallization with dichloromethane as the solvent. The employment of a slow solvent evaporation process proved beneficial in yielding monoclinic single crystals. The morphologies of the two types of single crystals were observed. The thermal stabilities and micro-morphologies of the OPS powders from the two crystals were characterized.