Enantiomer-selective radical cyclopolymerization of rac-2,4-pentanediyl dimethacrylate using a ruthenium-mediated chiral atom transfer radical polymerization initiating system |
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Authors: | Masashi Tsuji Towako Aoki Ryosuke Sakai Toshifumi Satoh Harumi Kaga Toyoji Kakuchi |
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Affiliation: | 1. Division of Molecular Chemistry, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan;2. Division of Molecular Chemistry, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan Division of Innovative Research, Creative Research Initiative Sousei, Hokkaido University, Sapporo 060-0808, Japan;3. National Institute of Advanced Industrial Science and Technology, Sapporo 062-8517, Japan |
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Abstract: | The enantiomer-selective radical polymerization of rac-2,4-pentanediyl dimethacrylate, an equimolar mixture of (2S,4S)-2,4-pentanediyl dimethacrylate (SS- 1 ) and (2R,4R)-2,4-pentanediyl dimethacrylate (RR- 1 ), was carried out with a chiral atom transfer radical polymerization initiating system consisting of methyl 2-bromoisobutyrate ( 3 ), dichlorotris(triphenylphosphine)ruthenium [RuCl2(PPh3)3], and a chiral additive in anisole at 60 °C. When (S)-1,1′-bi-2-naphthol ( a-3 ) was used as the chiral additive, the recovered monomer was enriched in SS- 1 , and the enantiomeric excess was 16.9% at a 22.6% monomer conversion. The specific rotation ([α]435, c 0.3, CHCl3) of the resulting polymer was +40.3° at a 22.6% monomer conversion. For the copolymerization of SS- 1 and RR- 1 with 3 /RuCl2(PPh3)3/ a-3 in anisole at 60 °C, the monomer reactivity ratio for RR- 1 (rR) was determined to be 4.94, and that for SS- 1 (rS) was 0.27. For the homopolymerizations of SS- 1 and RR- 1 with 3 /RuCl2(PPh3)3/ a-3 in anisole at 60 °C, the polymerization rate of RR- 1 was considerably faster than that of SS- 1 , and the rate constants for the homopolymerizations were determined to be kSS = 2.0 × 10−3 h−1 and kRR = 8.2 × 10−3 h−1, respectively. With the values of kSS, kRR, rR, and rS, the relative ratio kSS/kRR/kSR/kRS was determined to be 1.2:4.9:4.5:1, which indicated that both the growing end of SS- 1 and that of RR- 1 preferentially reacted with RR- 1 . © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4563–4569, 2004 |
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Keywords: | atom transfer radical polymerization (ATRP) chiral cyclopolymerization enantiomer-selective polymerization kinetics (polym.) optically active polymers racemic monomer rate constant |
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