• The term unsaturated monomers as used in this application includes any readily polymerizable vinyl aromatic monomer, e.g., styrene, ??-methylstyrene, vinyltoluene, divinylbenzene and structural isomers, derivatives and mixtures thereof or acrylic monomer, such as acrylic acid, methacrylic acid or their esters and amides and mixtures thereof or unsaturated esters such as vinyl acetate and unsaturat