The Microstructure Of Poly(Cyclopentene Carbonate)

The alternating copolymerization of carbon dioxide and epoxides to produce polycarbonates is an important green polymerization. In recent decades, we have witnessed significant developments in improving the catalyst activity, understanding the polymerization mechanism and controlling the ploymer stereochemistry. Stereoregularity has a great influence on the physical properties and biodegradation of the polycarbonates. Therefore, accurate control of polymer micro structure is a challenge goal in this field.Recently, our group has reported a chiral catalyst system based on enantiopure dinuclear Co(III) complexes with a rigid bridging biphenyl linker, which exhibited excellent activity, unprecedented enantioselectivity, and molecular-weight control for the alternating copolymerization of CO2 with meso-epoxides (including cyclopentene oxide and cyclohexene oxide) under mild reaction conditions. However, it is very difficult to give the accurate assignation of the microstructure of poly(cyclopentene carbonate), due to the complexity of split at the carboxyl region in the 13C NMR spectrum.In this dissertation (R,R)/(S,S)-cyclopentane-1,2-diols were used to synthesize two kinds of model dimer compounds:isotactic and syndiotactic diad oligomers. By comparing the signals in 13C NMR spectroscopy, we concluded that the signals at 153.57 ppm and 82.39 ppm of the copolymer are attributed to m-diad for the carbonyl and methine resonances, while that of 153.50 ppm and 82.26 ppm are assigned to r-diad for the carbonyl and methine resonances respectively.This dissertation also gives the 1H NMR study of poly(cyclopentene carbonate). The accurate assignation of various hydrogen atoms in the 1H NMR spectra was realized, and thereby benefiting for the mechanistic understanding of the coupling effect of different hydrogens.