High Molar Mass Poly(ε-caprolactone) by Means of Diphenyl Bismuth Ethoxide, a Highly Reactive Single Site Initiator

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• 作者：Hans R. Kricheldorf ; Gesa Behnken ; Gert Schwarz ; Juergen Kopf
• 刊名：Macromolecules
• 出版年：2008
• 出版时间：June 24, 2008
• 年：2008
• 卷：41
• 期：12
• 页码：4102 - 4107
• 全文大小：580K
• 年卷期：v.41,no.12(June 24, 2008)
• ISSN：1520-5835

文摘

Diphenylbismuth ethoxide, Ph₂BiOEt, initiates the ring-opening polymerization of ε-caprolactone via a coordination-insertion mechanism. The matrix assisted laser induced desorption and ionization-time-of-flight (MALDI−TOF) mass spectra proved the formation of one ethyl ester and one CH₂OH endgroup. The reactivity of this initiator is high enough to allow even for polymerizations at 20 °C. At 120 °C the reactivity of Ph₂BiOEt is lower than that of tin(II) 2-ethylhexanoate (SnOct₂) + ethanol, whereas below 90 °C, the reactivity of Ph₂BiOEt is higher. Small amounts of cyclic oligoesters are even formed at 20 °C. At 120 °C the number average molecular weights (M_ns) parallel the monomer-initiator ratios, and M_ns up to 115 000 Da were obtained. The time−conversion curves and the crystal structure indicate association of Ph₂BiOEt via O → Bi donor–acceptor interactions.