Synthesis of three- and six-arms polystyrene via living/controlled free radical polymerisation

Three new polyfunctional TEMPO-based initiators have been synthesised by reaction of some mesitylene cores and 2,2,6,6-tetramethyl-1-(2-hydroxy-1-phenylethoxy)-piperidine. They have been employed in the living/controlled radical polymerisation of styrene to provide three- and six-arm star macromolecules. These polymers have molecular weight ranging from 6000 to 11000 g/mol and narrow molecular weight distributions (PD<1.3). Cleavage of the link between the core and the arms was achieved, using a two-step sequence implying the preliminary removal of the TEMPO chain ends followed by catalytic hydrogenolysis. The dimensions of the individual arms so obtained closely match the values expected from the styrene/initiator molar ratio in the polymerisation feed.