Initiator Control of Conjugated Polymer Topology in Ring-Opening Alkyne Metathesis Polymerization

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• 作者：Stephen von Kugelgen ; Donatela E. Bellone ; Ryan R. Cloke ; Wade S. Perkins ; Felix R. Fischer
• 刊名：Journal of the American Chemical Society
• 出版年：2016
• 出版时间：May 18, 2016
• 年：2016
• 卷：138
• 期：19
• 页码：6234-6239
• 全文大小：390K
• 年卷期：0
• ISSN：1520-5126

文摘

Molybdenum carbyne complexes [RC≡Mo(OC(CH₃)(CF₃)₂)₃] featuring a mesityl (R = Mes) or an ethyl (R = Et) substituent initiate the living ring-opening alkyne metathesis polymerization of the strained cyclic alkyne, 5,6,11,12-tetradehydrobenzo[a,e][8]annulene, to yield fully conjugated poly(o-phenylene ethynylene). The difference in the steric demand of the polymer end-group (Mes vs Et) transferred during the initiation step determines the topology of the resulting polymer chain. While [MesC≡Mo(OC(CH₃)(CF₃)₂)₃] exclusively yields linear poly(o-phenylene ethynylene), polymerization initiated by [EtC≡Mo(OC(CH₃)(CF₃)₂)₃] results in cyclic polymers ranging in size from n = 5 to 20 monomer units. Kinetic studies reveal that the propagating species emerging from [EtC≡Mo(OC(CH₃)(CF₃)₂)₃] undergoes a highly selective intramolecular backbiting into the butynyl end-group.