Wagging bands, amorphous methylene

The amorphous methylene wagging bands show a temperature behavior which is more amenable to discussion. The 1352 cm" band has been calculated to result from the deformation of the methylene isolated by the GG conformation (55,56). The intensity of this band increased at elevated temperatures relative to the other amorphous wagging modes as a consequence of the higher energy of its conformation (55,56). This was also observed in the present work for the slow-crystallized sample. However, increases for the rapidly quenched systems only occurred after... 

The absorption bands of interest in the IR spectrum of PE are in the region 1425-600 cm Crystalline and amorphous phases contribute to vibrations observed within these limits (62). Amorphous methylene wagging vibrations are observed at 1369, 1353, and 1303 cmThe broad peak at 1078 cm has been assigned to the C-S stretching vibration of the amorphous phase. 

Polyethylene (PE) is the most-studied example of rotational isomerism. The crystalline domains are made up of the all-trans conformer structure. Bands that are characteristic of rotamers in the amorphous phase are also present. The most intense of the amorphous absorptions are the methylene wagging modes at 1303, 1353 and 1369 cm . The TG conformation is correlated with the bands observed at 1303 and 1369 cm . The 1353-cm absorption band is assigned to the wagging of the GG structure. When PE is heated through its melting point, the concentration of the TG and GG conformations increases. However, the concentration of the TG conformation increases well below the melting point, and this increase indicates the formation of localized conformational defects in the crystalline polymer. 

The 725 cm" rocking mode doublet is presented in Figure 3. The peaks at 731 and 720 cm for this sample are approximately 15 times the intensity of the amorphous wagging modes. The 720 cm limiting frequency is assigned to long trans sequences in the amorphous and crystalline phases. For these samples, most of the methylene structures are in the crystal, and the band is associated with this phase predomi-... 

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