Branching in Ethylene - Higher Olefin Copolymers

a six-carbon branch produces the same spectral pattern as any subsequent branch of greater length. C-NMR, alone cannot therefore be used to distinguish a linear six-carbon from a branch of some intermediate length or a true long chain branch. 

De Footer and co-workers [59] have applied C-NMR spectroscopy at sample temperatures of 130 °C to branching studies of copolymers of ethylene with 1-10 mol% of propylene, butane-1, hexane-1, octane-1 and 4-methyl pentene-1. C-NMR spectra were recorded with proton noise decoupling to remove unwanted scalar 

The terminology used by De Footer and co-workers [59] for branching is that commonly accepted, using an octene-1 copolymer as example  

This investigation included the chemical shift assignments (relative to that of the isolated methylene carbons at 30.0 ppm) and a set of experimental conditions for the quantitative analysis of branching in the most commercial types of linear LDPE. The integration limits given in Table 10.9 not only take into account the isolated branches, but also branches which are separated by one ethylene unit and branches next to each other. These latter two structures occur very infrequently in most commercial products but are significant to the calculations. 

Copolymer Area Region (ppm) Copolymer Area Region (ppm) 

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Short Chain Branching in Ethylene-Higher Olefin Copolymers... 

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