Synthesis of star-shaped poly(ϵ-caprolactone) by samarium-based tetrafunctional initiator and its dilute-solution properties
✍ Scribed by Xiujuan Xi; Liming Jiang; Jun Ling; Weilin Sun; Zhiquan Shen
- Publisher
- John Wiley and Sons
- Year
- 2006
- Tongue
- English
- Weight
- 123 KB
- Volume
- 102
- Category
- Article
- ISSN
- 0021-8995
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✦ Synopsis
Abstract
An in situ–generated tetrafunctional samarium enolate from the reduction of 1,1,1,1‐tetra(2‐bromoisobutyryloxymethyl)methane with divalent samarium complexes [Sm(PPh~2~)~2~ and SmI~2~] in tetrahydrofuran has proven to initiate the ring‐opening polymerization of ϵ‐caprolactone (CL) giving star‐shaped aliphatic polyesters. The polymerization proceeded with quantitative conversions at room temperature in 2 h and exhibited good controllability of the molecular weight of polymer. The resulting four‐armed poly(ϵ‐caprolactone) (PCL) was fractionated, and the dilute‐solution properties of the fractions were studied in tetrahydrofuran and toluene at 30°C. The Mark–Houwink relations for these solvents were [η] = 2.73 × 10^−2^M~w~^0.74^ and [η] = 1.97 × 10^−2^M~w~^0.75^, respectively. In addition, the unperturbed dimensions of the star‐shaped PCL systems were also evaluated, and a significant solvent effect was observed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 175–182, 2006