An immobilized/soluble hybrid catalyst system (CuBr/PS8-dMbpy)/(CuBr2/Me6TREN) for atom transfer radical polymerization (ATRP) was applied to the preparation of polymers exhibiting various architectures. Polymers with high degree of halogen chain end functionality (∼85%) were obtained using the hybrid catalyst system ensuring high efficiency of chain extension reactions through successive monomer addition, affording block (tapered) copolymers. Use of the immobilized catalyst also allowed the synthesis of block copolymers using macroinitiators synthesized by other mechanisms, such as poly(dimethylsiloxane). In the copolymerization of MMA and n-butyl acrylate, the molecular weight, molecular weight distribution, kinetics, and reactivity ratios were similar to those in a conventional homogeneous ATRP, indicating the chemical nature of the polymerization intermediates are similar for both systems. These examples demonstrate the broad applicability of the hybrid catalyst system to various ATRP processes.

The molecular structures of two 2,6-dimesitylphenyl derivatives of trivalent ytterbium are reported, representing first examples of organolanthanide complexes with a sterically demanding terphenyl ligand system as the only organic substituent at the metal center. For example, the molecular structure of a base adduct of DmpYbCl2 (shown) features a monomeric complex with a distorted octahedral coordination environment about the metal center.

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