Study on the Stereoregularity of Polyacrylonitrile Produced by Precipitation Polymerization in Supercritical CO_2

摘要

The triad and pentad tacticities of PAN obtained by precipitation polymerization in supercritical carbon dioxide, using AIBN ans initiator, (hereafter, referred as CO_2-PAN) were analyzed by ~(13)C NMR and IR method. The pentad tacticities of CO_2-PAN from the intensities of cyano peaks were examined by statistical methods. It was found that CO_2-PAN was completely random in stereoregularity, and the sequence distributions of it obey Bernoulli statistics. Compared with the aqueous phase suspension polymerization of AN, using AIBN as initiator, (hereafter, referred as S-PAN) and aqueous phase precipitation polymerization of AN, using redox type initiator, (hereafter, referred as R-PAN), it was found isotacticity of CO_2-PAN was lower than those of S-PAN and R-PAN, although the three kinds of PAN were all random in stereoregularity. The reason is probably due to the different poalr property of solvent. used. The relation between IR data and stereoregularity of PAN has also been used tocalculate the isotactic triad units of CO_2-PAN, the results is accordant with the ~(13)C NMR method used.