The present invention relates to a block copolymer prepared by ATRP, wherein the polymer chain terminal group is structurally modified with the functionally effective group of a lubricant or polymer additive selected from the group consisting of antioxidants, metal deactivators, antiwear and extreme pressure additives and corrosion inhibitors. The invention also relates to a composition comprising the structurally modified block copolymer and a composition of matter subject to oxidative, thermal or light induced degradation, such as lubricants or polymers.