Styrene

Styrene (C₈H₈) is vinylbenzene — a benzene ring crowned with a reactive vinyl group, a flamboyant star of the monomer world. It is the parent of an illustrious polymer lineage: polystyrene (PS), SBR, and ABS, and embodies the airy lightness of expanded polystyrene foam. Left alone it will spontaneously polymerize — a passionate soul that "heats up" so readily it needs an inhibitor just to be shipped. Boiling at 145°C with a sweet aroma, it is the theatrical ringmaster of the family, shadowed by an IARC Group 2A designation.