Synthesis of Triblock Copolymer Brushes by Surface-Initiated Atom Transfer Radical Polymerization

Surface-tethered triblock copolymers composed of poly(methyl acrylate), poly(methyl methacrylate), and poly(2-hydroxyethyl methacrylate) were grown from gold substrates by a series of atom transfer radical polymerizations at ambient temperature. GPC determinations of the molecular weights of desorbed triblock homopolymers suggest that this method can yield relatively homogeneous polymer brushes. To quench polymerization after the synthesis of each block, films were either exposed to a large excess of Cu(II)Br 2 or simply rinsed with solvent. Comparison of the thicknesses of multiblock homopolymer films with the thicknesses of films prepared using a single initiation step shows that in the Cu(II) quenching approach >95% of the active chains support growth of an additional block. However, for simple solvent rinsing between blocks, only 85−90% of active chains were preserved during the quenching step.