Copper-Catalysed “Activators Regenerated by Electron Transfer” “Atom Transfer Radical Polymerisation” of Styrene from a Bifunctional Initiator in Ethyl Acetate/Ethanol, Using Ascorbic Acid/Sodium Carbonate as Reducing System

A new copper(II) chloride/tris(2-piridylmethyl)amine (1/1) catalysed “Activators Regenerated by Electron Transfer” “Atom Transfer Radical Polymerisation” (ARGET ATRP) process for the polymerisation of styrene is described. The salient features of the method are the simultaneous use of ascorbic acid (reducing agent) and Na2CO3 (basic agent), the employment of a bifunctional initiator (ethyl 2,2-dichloropropionate) and the utilisation of a green solvent mixture composed of ethyl acetate and ethanol (AcOEt/EtOH). Na2CO3 plays a central role since not only preserves the ligand from protonation, but it can also activate the reducing agent. The quantity of monomer in the reaction mixture, the AcOEt/EtOH ratio and the load of ascorbic acid/carbonate are important factors for achieving a regular transformation. Working at 100 °C and with a metal load of only 0.025 mol%, an almost perfectly controlled telechelic polystyrene is produced, provided that conversion is kept below 50%. If conversion is higher, the control is gradually lost due superimposition of a step-growth process to the main chain polymerisation process. Two interesting phenomena, encountered during this study, are activation of the redox complex by using only Na2CO3 and gelation of polystyrene at 60 °C.