Abstract: The present invention relates to a polymerization process for the synthesis of vinyl aromatic polymers, in which the sequence of monomers in the chain and the linear, branched soluble, or crosslinked insoluble structure, with reactive or different polarity functions, are controlled. Said process comprises the step of polymerizing vinyl aromatic monomers by means of an Atom Transfer Radical Polymerization (ATRP) reaction with an Activator ReGenerated by Electron Transfer (ARGET), the reaction being carried out at a temperature comprised between 25° C. and 110° C. in an inert gas atmosphere in the presence of a complex catalyst containing a cupric halide and a multidentate amine ligand, feeding to the reaction an organic initiator having two geminal halogens, an alkali metal (bi)carbonate, a solvent pair of an aliphatic alcohol and an acetic ester of the same aliphatic alcohol and possibly ascorbic acid, provided that no initiator is used with three or more active halogens, or polyvinyl monomers or inimers.