Highly Efficient Synthesis of Low Polydispersity Core Cross-Linked Star Polymers by Ru-Catalyzed Living Radical Polymerization

The efficient formation of low polydispersity core cross-linked star (CCS) polymers via controlled/living radical polymerization (LRP) and the arm-first approach was found to be dependant on the mediating catalyst system. The Ru catalyst, Ru(Ind)Cl(PPh3)(2) Cat. 1, and tertiary amine co-catalyst were used to synthesize highly living poly(methyl methacrylate) (PMMA) macroinitiators, which were then linked together with ethylene glycol dimethacrylate (EGDMA) to form PMMA(arm)-PEGDMA(core) CCS polymers. The quantitative and near-quantitative synthesis of CCS polymers were observed for low to moderate molecular weight macroinitiators ((M) over bar (n) = 8 and 20 kDa), respectively. Lower conversions were observed for high-molecular weight macroinitiators ((M) over bar (n) >= 60 kDa). Overall, an improvement of between 10 and 20% was observed when comparing the Cat. 1 system to a conventional Cu-catalyzed system. This significant improvement in macroinitiator-to-star conversion is explained in the context of catalyst system selection and CCS polymer formation.