Styrenated oil was obtained by nitroxide mediated radical polymerization (NMRP) method in the presence of 2,2',6,6'-tetramethylpiperidinyl-l-oxy (TEMPO). For this purpose, firstly, macroinitiator having thermally unstable azo groups was obtained with reaction of partial glycerides (PGs) mixture and 4,4'-azobis-4-cyanopentanoyl chloride (ACPC). Then, the macroinitiator was subjected to polymerization with styrene in the presence of TEMPO in order to obtain a copolymer with controlled structure and low poly-dispersity. The products thus obtained were characterized by GPC, H-1 NMR and FT-IR measurements. A classical styrenated oil was also prepared for comparison. The film properties of the products were determined according to the related standards and compared with each other. The product obtained at the end of the 72 h in the presence of TEMPO showed to some extent brittle film properties. To improve the film properties, this product was further reacted with the oil-based vinyl macromonomer (MM). The styrenated oil samples prepared by the controlled polymerization method, exhibited relatively low polydispersity (<1.5) and showed good film properties. (C) 2009 Elsevier B.V. All rights reserved.