International audienceA controlled polymerisation of styrene has been achieved under ATRP conditions by using a phosphine-containing MoIII/MoIV system. Linearity of the Mn vs conversion plot and low PDI’s are observed in bulk, in a 30% (v/v) PhCl solution, and in a chain extension experiment when using MoCl3(PMe3)3/BIB. Controlled polymerisation is also observed for a reverse ATRP experiment starting from MoCl4(PMe3)3/AIBN. The absence of chain transfer and termination is confirmed by NMR and MALDI–TOF analyses of polymers obtained by employing BEB and BIB as initiators.Cet article décrit la possibilité d'effectuer une polymérisation contrôlée du styrène en utilisant un système de complexes de coordination de MoIII/MoIV contenant des ligand...