• Summary

NM130011E

In solid-state NMR, DDMAS spectra (single-pulse decoupling MAS spectra) measured with a  sufficiently long recycle delay may provide quantitative information. The signal inteisities of the 13C  DDMAS spectrum for low-density polyethylene (LDPE; density 0.915) shown below can draw  some quantitative conclusions on its microstructures.

低密度ポリエチレン(比重0.915)試料に対する13C DDMASスペクトルの信号強度

Crystallinity

The crystallinity of the sample is evaluated to be approximately 46% from the main CH2 peak  intensity for crystalline phase (32.84 ppm) and that for amorphous phase (30.77 ppm).

Molecular weight

The intensity ratio of the peak at 23.32 ppm, assigned to the a-CH2 in the main chain, and the main  peaks at 32.84 and 30.77 ppm proves that the number of CH2 monomer units is about 300 and the  molecular weight Mw is about 4,000.

Branching ratio

For example, the intensity ratio of the peaks at 23.75 and 38.24 ppm and the main peaks shows  that the following one branching structure exists within 50-60 CH2 units.

For example, the intensity ratio of the peaks at 23.75 and 38.24 ppm and the main peaks shows  that the following one branching structure exists within 50-60 CH2 units.

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