An Efficient Method of Depolymerization of Poly(cyclopentene carbonate) to Its Comonomers: Cyclopentene Oxide and Carbon Dioxide
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The hydroxyl-terminated copolymer, poly(cyclopentene carbonate), derived from carbon dioxide and cyclopentene oxide was deprotonated by the strong base sodium bis(trimethylsilyl)amide (NaHMDS) in toluene and shown to undergo depolymerization to cyclopentene oxide and cis-cyclopentene carbonate. The degradation process was demonstrated to be retarded under a 0.7 MPa pressure of CO2, with the product distribution being enhanced in favor of cis-cyclopentene carbonate. Unlike the related copolymer, poly(indene carbonate), the degradation pathway was found to be insensitive to either light or the radical trap, TEMPO. The depolymerization process was further shown to be catalyzed by (salen)CrCl/n-Bu4NN3, with the major product being cyclopentene oxide. Although the reaction rate in the presence of metal catalyst was inhibited by an added pressure of CO2, the product distribution still highly favored epoxide production. On the other hand, upon reducing the pressure above the polymer solution during the depolymerization reaction, the rate of reaction was accelerated and was more selective for cyclopentene oxide formation. Preliminary studies were investigated to optimize the efficient recycling of poly(cyclopentene carbonate) to its monomers, cyclopentene oxide and CO2. Computational studies have been performed on depolymerization reaction of polycarbonates derived from CO2 and epoxides which strongly support these experimental findings. 2013 American Chemical Society.