Iron(II)-catalyzed suspension living radical polymerizations of acrylates and styrene have been achieved for the first time in water. In the presence of a large amount of water (water/organic = 1/1 v/v), a half-metallocene type iron complex [Fe(Cp)I(CO)2] induced a smooth polymerization of n-butyl acrylate in conjunction with (CH3)2C(CO2Et)I as an initiator to give polymers of narrow molecular weight distributions (MWDs) (M w/M n = 1.2−1.3) and controlled number-average molecular weights, in direct proportion to monomer conversion. Reaching 90% conversion in 4 h, the polymerizations proceeded much faster than in toluene without water. Similarly, methyl acrylate, tert-butyl acrylate, and styrene were polymerized with the same initiating system under aqueous suspension conditions to afford living polymers of controlled molecular weights and narrow MWDs (M w/M n = 1.2−1.3). The suspension systems can be applied to the controlled synthesis of block and random copolymers of acrylates and styrene.

A hydrophilic ruthenium complex with ionic phosphine ligands {1: RuCl2[P(3‐C6H4SO3Na)(C6H5)2]2} induced controlled radical polymerization of 2‐hydroxyethyl methacrylate (HEMA) in methanol under homogeneous conditions; the initiator was a chloride (R‐Cl) such as CHCl2COPh. The number‐average molecular weights of poly(HEMA) increased in direct proportion to monomer conversion, and the molecular weight distributions were relatively narrow (Mw/Mn = 1.4–1.7). A similar living radical polymerization was possible with (MMA)2‐Cl [(CH3)2C(CO2CH3)CH2C(CH3)(CO2CH3)Cl] as an initiator coupled with amine additives such as n‐Bu3N. In a similar homogeneous system in methanol, methyl methacrylate (MMA) could also be polymerized in living fashion with the R‐Cl/1 initiating system. Especially for such hydrophobic polymers, the water‐soluble ruthenium catalyst was readily removed from the polymers by simple washing with an aqueous dilute acid. This system can be applied to the direct synthesis of amphiphilic random and block copolymers of HEMA and MMA. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2055–2065, 2002

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