2DIR studies on polyethylene

We used the two-dimensional FT-IR spectroscopy cooperated with high resolution and cryogenic techniques to investigate the CH2 rocking bands (750-700 cm−1) of HDPE. The 2D asynchronous spectra showed multiple forms of orthorhombic polyethylene co-existed. For the two orthorhombic bands around 730 and 720 cm−1, each band is composed of at least two sub-bands. The differences in peak position for the sub-bands are less than 1 cm−1. Thus the overlapping for the sub-bands is so severe that the sub-bands are hardly observed by conventional resolution enhancement methods. The co-existence of multiple orthorhombic polyethylene got supports from NMR studies.