Pentad observed probabilities

Table HI. Observed Probabilities of Regiosequence Pentads (P0bS(S5) as defined in reference 2) for Aregic PVF Samples ...

Several peaks arising from different pentad and hexad comonomer sequences have been observed n the C-NMR spectrum of stereoregular 1-butene-propylene copolymers. The paper by Aoki and co-workers [54] demonstrated that the analytical method based on the two-dimensional (2D)-INADEQUATE spectrum and the chemical shift calculation via the y-effect is very powerful for the assignment of C-NMR spectra of higher a-olefin copolymers. A stereoregular 1-butene-propylene copolymer is a suitable example because reliable assignments have been proposed by a reaction probability model [55]. 

The lack of chemical shift at 66 ppm due to the CH2 groups of PVCN suggests a mostly alternating structure of these copolymers. The structure of these products would be alternating and terminated by homosequences of MAN or CVA. The examination of CN groups in p(VCN-MAN) is in good agreement with this proposition three CN peaks are observed for the MAN units due to the three different pentads denoted M M, R M and R R. The most important peak is probably due to the R R pentad. 

---