Cobalt‐mediated radical polymerization routes to poly(vinyl ester) block copolymers |
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Authors: | David N Bunck Gregory P Sorenson Mahesh K Mahanthappa |
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Institution: | Department of Chemistry, University of Wisconsin–Madison, 1101 University Ave., Madison, Wisconsin 53706 |
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Abstract: | Cobalt‐mediated radical polymerizations (CMRPs) utilizing redox initiation are demonstrated to produce poly(vinyl ester) homopolymers derived from vinyl pivalate (VPv) and vinyl benzoate (VBz), and their block copolymers with vinyl acetate (VAc). Combining anhydrous Co(acac)2, lauroyl peroxide, citric acid trisodium salt, and VPv at 30 °C results in controlled polymerizations that yield homopolymers with Mn = 2.5–27 kg/mol with Mw/Mn = 1.20–1.30. Homopolymerizations of scrupulously purified VBz proceed with lower levels of control as evidenced by broader polydispersities over a range of molecular weights (Mn = 4–16 kg/mol; Mw/Mn = 1.34–1.65), which may be interpreted in terms of the decreased nucleophilicity of these less electron donating propagating polymer chain ends. Based on these results, we demonstrate that sequential CMRP reactions present a viable route to microphase separated poly(vinyl ester) block copolymers as shown by small‐angle X‐ray scattering analyses. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 |
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Keywords: | biodegradable block copolymers cobalt‐mediated radical polymerization (CMRP) degenerate transfer polymerization radical polymerization self‐assembly vinyl acetate vinyl ester |
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