Sulfonyl chlorides: Universal initiators for metal catalyzed living radical polymerization

Radical polymerization is widely employed in industrial- and laboratory-scale processes for polymer synthesis because it has a high reaction rate at a convenient, higher than ambient temperature, and it also tolerates protic “impurities”. For precision polymer synthesis, the most used method is “living” polymerization and it provides control over the molecular weights, molecular weight distributions, and chain end functionality. Independent from each other, our and other two groups published in 1995 the first papers claiming the living radical polymerization (LRP) of methacrylates and styrene (S), and propelled this field of research to new frontiers. We first reported the CuCl/bpy catalyzed bulk LRP of S initiated with benzenesulfonyl chloride and its derivatives and proposed a novel mechanism. The resulting living polymers have a chain end derived from the arylsulfonyl radical and one containing a chloride atom. The CuCl/bpy catalysis in this polymerization is heterogeneous. A step further was the transformation of the catalysis process from heterogeneous to homogeneous . Detailed mechanistic investigations and the determination of apparent rate constants for initiation and propagation steps in the homogeneous CuCl catalyzed LRP of S, methyl methacrylate (MMA), butyl methacrylate (BMA), methyl acrylate (MA), acrylonitrile (AN) and butyl acrylate (BA) demonstrate that arylsulfonyl chlorides are the first universal class of functional initiators. Novel Cu2O and Cu(0) catalysts, in conjunction with bpy, self-regulate the LRP of S, AN, MMA and BMA by generating small amounts of active CuCl species in situ. The Cu2O catalyst was used in the aromatic multisulfonyl chloride initiated LRP of S, AN, MMA and BMA to produce polymers with star architectures. It was time, then, to go back and use the tools we developed in polymer synthesis for organic synthesis, and by blending the two synthetic areas to generate a novel concept, TERMINI. TERMINI stands for TERminator Multifunctional INItiator and it is a novel synthetic concept for the synthesis of dendritic macromolecules via LRP or other living polymerization techniques, in a divergent or convergent fashion. The TERMINI concept has been demonstrated by the synthesis of a novel class of macromolecules with a dendritic architecture