Aqueous metal-catalyzed living radical polymerization: highly active water-assisted catalysis

作者：Ouchi Makoto^*; Yoda Hiroaki; Terashima Takaya; Sawamoto Mitsuo

来源：Polymer Journal, 2012, 44(1): 51-58.

DOI：10.1038/pj.2011.59

• aqueous polymerization
• block copolymerization
• catalyst
• living radical polymerization
• phosphine
• ruthenium

Catalytic aqueous living radical polymerization was achieved through a ligand design for a ruthenium-based catalyst. A phenolic phosphine ligand [PPh(2)(pPhOH)] was combined with a pentamethylcyclopentadienyl (Cp*)-based tetrameric ruthenium precursor, and the resulting complex showed a high catalytic activity for aqueous living radical polymerizations of hydrophilic methacrylates (for example, poly(ethylene glycol) methacrylate and 2-hydroxyethyl methacrylate) in conjunction with a chlorine initiator [H-(MMA)(2)-Cl]. The catalytic system allowed very fast living polymerizations, block copolymerizations and syntheses of high-molecular-weight polymers (DP(n)similar to 1000) with narrow-molecular-weight distributions. Importantly, the activity was high enough to control the polymerization using a catalytic amount of the complex, even though the polymerizations were performed at low temperature (40 degrees C). Such advanced catalysis was achieved by not only simple hydrophilicity of the ligand but also by a water-assisted dynamic transformation from the original coordinatively saturated form [Cp*RuCl(PR(3))(2); 18e; PR(3)=phosphine] into an unsaturated and active form [Cp*RuCl(PR(3)); 16e]. Water molecule(s) may also coordinate for further stabilization as demonstrated by (31)P NMR analyses. Polymer Journal (2012) 44, 51-58; doi:10.1038/pj.2011.59; published online 3 August 2011

• 出版日期2012-1