This invention provides a method by which an alkylstyrene containing polymer may be exclusively functionalized at the primary benzylic carbon site of the styrenic monomer. The process of this invention comprises the treatment of an alkylstyrene containing polymer dissolved in a non-polar liquid medium with an organic hydroperoxide oxidizing reagent in the presence of a catalytically sufficient amount of a chromium compound, to oxidize a portion of the aromatic alkyl groups of the polymer to an oxygen containing functional group.