A common route to A2B and A3B multiarm star block copolymers

We have previously described a new route to A2B star block copolymers by a double addition–elimination reaction of a polystyryl carbanion with a particular 1,1-diphenylethylene derivative. By using the same reagent, we are now able to prepare A2 or A3 homopolymers by changing the solvent, i.e. tetrahydrofuran or toluene/tetrahydrofuran, respectively. We propose a mechanism involving nucleophilic substitution reactions to explain this peculiar result and use this opportunity to prepare A2B or A3B star block copolymers based on styrene and ethylene oxide or tert-butyl methacrylate.