Polyethylene mixed crystal infra-red spectroscopy: The influence of matrix isotopic species on guest conformation

The chain conformation of solution-crystallized polyethylene has previously been confirmed by infra-red spectroscopy, using the CD₂ bending bandshape for samples with a minority of the deuterated species^1–3. The method of calculating the i.r. band profile from molecular conformational models is now developed to give a more accurate representation of doublet splittings and to include the singlet component. The CH₂ bending profile is calculated for samples with a deuterated matrix, and the good agreement with experimental data indicates that the same molecular model is applicable for samples with the deuterated polymer as either guest or matrix, for identical crystallization conditions. This result implies that isotopic fractionation is unimportant under these conditions.