Wagging modes, amorphous absorptions

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. 

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