Synthesis of mikto‐topology star polymer containing one cyclic arm

Well‐defined mikto‐topology star polystyrene composed of one cyclic arm and four linear arms was synthesized by a combination of atom transfer radical polymerization (ATRP) and Cu‐catalyzed azide‐alkyne cycloaddition (CuAAC) click reaction. First, the bromine‐alkyne α,ω‐linear polystyrenes containing four hydroxyl groups protected with acetone‐based ketal groups were synthesized by ATRP of styrene using a designed initiator. Then, the bromine end‐group was converted to the azide and the linear polystyrene was cyclized intra‐molecularly by the CuAAC reaction. The four hydroxyl groups were released by deprotection and then esterified with 2‐bromoisobutyryl bromide to produce a cyclic polymer bearing four ATRP initiating units. By subsequent ATRP of styrene to grow linear polymers with the cyclic polystyrene as a macroinitiator, the mikto‐topology star polymers were prepared. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012