A Supramolecular Strategy for the Synthesis of Cyclic Oligomers and Polymers by Ring Expansion |
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Authors: | Dr Michael Duss Dr Miguel A Soto Dr Brian O Patrick Prof Mark J MacLachlan |
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Institution: | Department of Chemistry, University of British Columbia, 2036 Main Mall, V6T 1Z1 Vancouver, British Columbia, Canada |
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Abstract: | Ring-opening metathesis polymerization (ROMP) of strained macrocycles is a key method to prepare diverse polymers. However, lack of ring strain in most macrocycles is an impediment to polymerization. In this paper, the polymerization/oligomerization of unstrained macrocycles was achieved using a supramolecular approach, leading selectively to cyclic products. Diphenyl thiourea and other guest molecules were used as additives to the ROMP reaction of unstrained macrocycles. An intermediate host-guest complex leads to the stabilization of the open form of the macrocycle after treatment with Grubbs catalysts, thereby favoring polymerization by inhibiting the ring-closing reaction back to the monomer. This proof-of-concept enables ring-expansion polymerization of unstrained macrocycles leading to cyclic polymers with molecular weights up to 6700 Da. |
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Keywords: | cyclic polymers host-guest chemistry macrocycle olefin metathesis supramolecular chemistry |
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