Synthesis of A2B star block copolymers from a heterotrifunctional initiator

We described the obtention of A2B star block copolymers through the use of a new heterotrifunctional initiator. That way, well‐defined (PCL)2‐arm‐PtBuMA and (PCL)2‐arm‐PS star block copolymers have been synthesized from a heterotrifunctional initiator bearing two hydroxyl groups able to initiate ROP of CL (with AlEt3 or Sn(Oct)2 as coinitiator) and a bromide function able to initiate ATRP of tBuMA or styrene. Firstly, we have proceeded using a sequential process (two‐steps), leading to an intermediate macroinitiator. Secondly, attempt to polymerize these two monomers in a simultaneous process (one‐step), that is directly from the mixture of monomers, initiator, coinitiators, and solvent, has been realized and has shown that some interferences between the two polymerizations occurred, leading to an inhibition of ATRP when Sn(Oct)2 was used and an unexpected increase in control when AlEt3 was used as catalyst for the ROP (obtention of well‐defined (PCL)2‐arm‐PtBuMA with pdi of 1.18). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1796–1806, 2006 Well‐defined (PCL)2‐arm‐PtBuMA (or PS) miktoarm star block copolymers were synthesized from a heteromultifunctional initiator bearing two OH (for the ROP of CL) and one Br (for the ATRP of tBuMA or styrene). This can be achieved in a sequential process through a PCL or PtBuMA (PS) macroinitiator or in a simultaneous way, i.e. directly from the two monomers and initiator mixture as described in the scheme.