Polypropylene heptad assignments

Spectra of model compounds are also utilized to assign stereochemical sequences in polymer.182 However, model compounds with defined stereochemical configurations are rather difficult to obtain. Zambelli et a/.183 reported that heptad models for polypropylene, 3(5), 5(R), 1 (RS), 9(RS),... 

The chemical shift calculation (y-effect method) based on the y-effect of the chemical shift and the rotational isomeric state model (RIS model) has been developed as a reliable method for predicting chemical shift differences among pentad, hexad, and heptad sequences in various polyolefins [47-49, 14, 50, 51]. chemical shift assignments of tactic pentad and heptad sequences in polypropylene have been provided by this method [47-49]. Hayashi and co-workers [45,46] confirmed that the chemical shift due to the y-effect is also sensitive to different comonomer sequences in ethylene-propylene copolymers. Asakura and co-workers [52] have demonstrated that... 

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