Effect of ligand on the synthesis of star polymers by resorcinarene-based ATRP initiators

The effect of the steric hindrance on the initiating properties of two multifunctional resorcinarene-based initiators in atom transfer radical polymerization (ATRP) was studied by using Cu(I)-complexes of three multidentate amine ligands in the polymerization of tert-butyl acrylate and methyl methacrylate. These ligands are less sterically hindered and have higher activities in the catalysis of ATRP of (meth)acrylates than 2,2'-bipyridine. The polymerizations were faster and more controlled than with the 2,2'-bipyridyl catalyst, but the tendency for bimolecular coupling increased. Even though the initiator was octafunctional, the resulting star polymers had only four arms. This indicates that the steric hindrance arising from the conformations of the initiators determines the structure of the polymer, but the ligand noticeably affects the controllability of the polymerization (c) 2005 Wiley Periodicals, Inc.