I.r. study of solution-grown crystals of polyethylene: correlation with the model from neutron scattering

Abstract

The crystal stem arrangement in solution-grown polyethylene crystals has been investigated by the mixed-crystal infra-red technique. Parallel neutron scattering measurements are reported separately. The behaviour of the CD 2 bending vibration is shown to be consistent with a model having 75% adjacent re-entry, 50% dilution of a molecule along the fold plane (110 direction) and a degree of superfolding equivalent to an average molecular weight ( M ̄ w ) of 21 000 for each sheet. This is in agreement with results from neutron scattering, which have previously been interpreted using this model. Computer calculations of stem positions based on these parameters are used to calculate the distributions of doublet splittings for several molecular weights. The main features of low-temperature FTi.r. spectra as a function of molecular weight are reproduced in this way.