Spectral assignment of poly[cyclohexene oxide-alt-carbon dioxide]

Signals of C-13 NMR spectra of poly[cyclohexene oxide-alt-carbon dioxide] in a carbonyl region split into two parts: 153.7 and 153.3-153.1 ppm. To assign these signals, isotactic and syndiotactic model dimers and tetramers were synthesized. The signals of isotactic oligomers appeared at 153.8 ppm, whereas the signals of syndiotactic isomers appeared at higher field and shifted to higher field (up to 153.1 ppm) on going from dimer to tetramer. These results led to the final assignment of the copolymer: the signal at 153.7 ppm includes isotactic diads, and the ones at 153.3-153.1 ppm include syndiotactie diads.