Abstract
A number of split peaks dependent on both comonomer sequences and stereosequences were observed in the 13C nuclear magnetic resonance (n.m.r.) spectrum of ethylene-propylene (E-P) copolymer. The 13C chemical shifts of methylene carbon in stereoisomers of the respective hexad comonomer sequences were predicted by a chemical-shift calculation using the gamma effect on 13C chemical shifts and Mark's rotational isomeric state model for E-P copolymer. Assignments of the split peaks that arise from different hexad stereosequences were given by comparison between the observed and calculated chemical shifts. Reference was made to the hexad assignments of comonomer-sequence-dependent peak splittings determined in our previous calculation of 13C n.m.r. chemical shifts of stereoregular E-P copolymers. The tacticities were estimated for successive (not separated by ethylene units) propylene units in the hexad sequences.
Published Version
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