C-13 NMR SPECTRAL ASSIGNMENT OF 5 POLYOLEFINS DETERMINED FROM THE CHEMICAL-SHIFT CALCULATION AND THE POLYMERIZATION MECHANISM

Assignments of the C-13 NMR spectra of five polyolefins, poly(1-pentene), poly(1-hexene), poly(1-heptene), poly(1-octene), and poly(1-nonene), to tacticity were performed from the C-13 NMR chemical shift calculation on the basis of the C-13 NMR gamma effect and application of the rotational isomeric state model. The origin of the complex spectral behavior of the methylene backbone carbon, C1, among a series of poly-olefins including polypropylene and poly(1-butene) was also successfully interpreted through the chemical shift calculation. The mechanisms of olefin polymerization were analyzed from the values of pentad tacticities obtained from the C3 carbon peak of the side chain on the basis of the bicatalytic sites model. The relative area of hexad peaks calculated with the three parameters optimized in the bicatalytic sites model was also used in the assignment of the C1 carbon peak.