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Abstract

It has been determined that metal salts of certain phenolic type antioxidants act as randomizers in the solution polymerization of conjugated diolefin monomers with copolymerizable vinyl aromatic monomers. These randomizers do not increase the vinyl content of polymers made in polymerizations which utilize them. These randomizers offer a special advantage in that they can be converted into antioxidants after polymerization has been completed in order to provide the polymer produced with stability against oxidation. The present invention specifically relates to a process for preparing a rubbery substantially random copolymer which comprises polymerizing at least one conjugated diolefin monomer with at least one copolymerizable vinyl aromatic monomer in the presence of an organolithium initiator and a randomizing agent having the structural formula ##STR1## wherein M is a metal from Group I of the periodic system, and wherein R.sup.1, R.sup.2, and R.sup.3 can be the same or different and are selected from alkyl groups, aryl groups, and tertiary-alkaryl groups, with the proviso that there is a collective total of at least 12 carbon atoms in R.sup.1, R.sup.2, and R.sup.3.

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First Claim