Cobalt-mediated radical polymerization of vinyl acetate: a new tool for macromolecular engineering

in Matyjaszewski, Krzysztof (Ed.) Controlled/living radical polymerization: from synthesis to materials (2006)

Synthesis of poly(vinyl acetate) and poly(vinyl alcohol) containing block copolymers by combination of cobalt-mediated radical polymerization and ATRP

in Macromolecules (2005), 38(23), 9488-9496

Poly(vinyl acetate) (PVAc) chains of a low polydispersity (Mw/Mn similar to 1.1-1.2) have been prepared by cobalt-mediated radical polymerization of vinyl acetate (VAc). They have been end-capped by an ... [more ▼]

Poly(vinyl acetate) (PVAc) chains of a low polydispersity (Mw/Mn similar to 1.1-1.2) have been prepared by cobalt-mediated radical polymerization of vinyl acetate (VAc). They have been end-capped by an activated bromide by addition of an alpha-bromoester or an alpha-bromoketone containing nitroxide and converted into effective macroinitiators for the atom transfer radical polymerization of styrene (Sty), ethyl acrylate, and methyl methacrylate. Because each block is formed by a controlled process, well-defined PVAc containing diblock copolymers are easily prepared. The PVAc-b-PS copolymers synthesized from alpha-bromoketone end-capped PVAc can be converted into well-defined poly(vinyl alcohol)-b-polystyrene amphiphiles by methanolysis of the poly(vinyl acetate) block. Self-association of an amphiphilic poly(vinyl alcohol)(3500)-b-polystyrene(16 600) in a (4/1) water/tetrahydrofuran mixture results in the formation of vesicles as observed by transmission electron microscopy. [less ▲]

Quinone transfer radical polymerization of styrene catalyzed by metal complexes in the presence of various o-quinones

in Macromolecules (2005), 38(15), 6310-6315

Several o-quinones have been tested as control agents for the quinone transfer radical polymerization (QTRP) of styrene in the presence of cobalt(II) acetylacetonate. In contrast to the commercially ... [more ▼]

Several o-quinones have been tested as control agents for the quinone transfer radical polymerization (QTRP) of styrene in the presence of cobalt(II) acetylacetonate. In contrast to the commercially available 3,5-di-tert-butyl-o-benzoquinone (3,5-DtBBQ) and tetrachloro-1,2-benzoquinone (tetrachloro-1,2-BQ), 3,6-dimethoxy-9,10-phenanthrenequinone (3,6-DMPhQ) imparts a better control to the radical polymerization of styrene compared to 9,10-phenanthrenequinone (PhQ) used as a reference. Indeed, whenever 3,6-DMPhQ is added with a catalytic amount of metal complexes (Co(acac)(2) or Al(acac)(3)), the evolution of the molar mass with the monomer conversion is linear, and low polydispersity (M-w/M-n similar to 1.1-1.2) is observed until very high monomer conversion (similar to 90%). Finally, the methoxy protons of 3,6-DMPhQ have been detected by H-1 NMR analysis of the polystyrene end groups, which is important mechanistic information. [less ▲]

Synthesis of end-functional poly(vinyl acetate) by cobalt-mediated radical polymerization

in Macromolecules (2005), 38(13), 5452-5458

Poly(vinyl acetate) (PVAc) chains prepared by cobalt-mediated radical polymerization in the presence of cobalt(II) acetylacetonate (Co(acac)(2)) were quenched by radical scavengers, such as thiol ... [more ▼]

Poly(vinyl acetate) (PVAc) chains prepared by cobalt-mediated radical polymerization in the presence of cobalt(II) acetylacetonate (Co(acac)(2)) were quenched by radical scavengers, such as thiol compounds and nitroxides, to displace the covalently bonded Co(acac)(2) moiety and to end-cap them with a reactive group. The cobalt complex was completely removed by filtration, as confirmed by the induction coupled plasma (ICP) analysis of the polymer before and after treatment. Growing poly(vinyl acetate) chains can be end-functionalized either by addition of an appropriately functionalized nonpolymerizable olefin or by displacement of the Co(acac)(2) moiety by a functionalized nitroxide. This strategy allows PVAc to be synthesized with a predictable molecular weight, a reasonably low polydispersity (M-w/M-n similar to 1.1-1.3), and a functional omega end group, e.g., hydroxyl and epoxy. [less ▲]

Highly efficient cobalt-mediated radical polymerization of vinyl acetate

in Angewandte Chemie (International ed. in English) (2005), 44(7), 1101-1104

Controlled radical polymerization of vinyl acetate based on cobalt(II) acetyl acetonate

in Chimie Nouvelle (2005)

Controlled radical polymerization (CRP) is a valuable strategy to design a large range of polymers with well defined molecular characteristics under non very demanding conditions. However, the known CRP ... [more ▼]

Controlled radical polymerization (CRP) is a valuable strategy to design a large range of polymers with well defined molecular characteristics under non very demanding conditions. However, the known CRP techniques, such as nitroxide mediated polymerization (NMP), atom transfer radical polymerization (ATRP) and radical addition-fragmentation chain transfer polymerization (RAFT), suffer from limitations, including a moderate control on the vinyl acetate polymerization. Within the search for new controlled radical polymerization processes, we designed a system based on the reversible combination of growing macroradicals with a cobalt(II)acetylacetonate complex which provides an effective control of the vinyl acetate polymerization even when carried out in suspension in water. In a macromolecular engineering effort, well-defined end-functional poly(vinyl acetate), and poly(vinyl acetate) or poly(vinyl alcohol) containing block copolymers have been synthesized. [less ▲]