13C NMR chemical shift assignments of comonomer sequences in a 1-butene-propylene copolymer were obtained from the 13C two-dimensional INADEQUATE NMR experiment and from the calculated chemical shifts due to the y effect. By tracing carbon-carbon connectivities in the 2D- INADEQUATE spectrum, the validity of previous assignments of triad and tetrad sequences was confirmed. Referring to the confirmed assignments, the chemical shift differences among comonomer sequences longer than pentad were predicted by the chemical shift calculation (the y-effect method) based on the y effect of the 13C chemical shift and Mark's rotational isomeric state model modified by considering the side-chain conformation in a 1-butene unit. Assignments provided in this study agree well with Cheng's assignments by a reaction probability model. Further, the conformational probability of the side chain in a 1-butene unit was evaluated through the chemical shift calculation.
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