Styrene oligomers (M-n, 2500-3000 g/mol) with low polydispersity index and containing peroxidic groups within their structure were synthesized using a novel trifunctional cyclic radical initiator, diethylketone triperoxide (DEKTP), through nitroxide-mediated radical polymerization (NMRP), using OH-TEMPO. During the synthesis of the polystyrene (PS) oligomers, camphorsulfonic acid (CSA) was used to inhibit the thermal autoinitiation of styrene at the evaluated temperatures (T = 120-130 degrees C). The polymerization rate, which can be related to the slope of the plot of monomer conversion with reaction time, was monitored as a function of OH-TEMPO, DEKTP, and CSA concentrations. The experimental results showed that all the synthesized polymers presented narrow molecular weight distributions, and the monomer conversion and the molecular weight of the polymers increased as a function of reaction time. Under the experimental conditions, T = 130 degrees C, [DEKTP] = 10 mM, and [DEKTP]/[OH-TEMPO] = 6.5, PS oligomers containing unreacted O-O sites in their inner structure were obtained. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 1320-1328, 2012