Examples of vinyl aromatic monomers are styrene, alpha methylstyrene, alkyl-substituted styrene monomers such as vinyl toluene and halogen-substituted styrene monomers such as chlorostyrene, bromostryrene, di- and tri-bromo styrene and the like, and illustrative of acrylic monomers are alkyl methacrylates including methyl methacrylate, butyl methacrylate, octyl methacrylate and the like, and the c