Motion in Polyethylene. II. Vibrations in Crystalline Polyethylene
- 15 September 1962
- journal article
- Published by AIP Publishing in The Journal of Chemical Physics
- Vol. 37 (6) , 1207-1216
- https://doi.org/10.1063/1.1733267
Abstract
Using the specific heats of completely crystalline polyethylene as a basis, the vibrational spectrum is discussed. The vibrational spectrum is found to consist of three completely separate parts. (A) The high-frequency CH2-stretching vibrations between 2850 and 2930 cm—1 which contribute little to the specific heat below 350°K. (B) The low-frequency optical vibrations between 720 and 1480 cm—1 which contribute above 150°K increasingly to the specific heat. (C) The acoustical vibrations which stretch from zero to approximately 500 cm—1 and are at 260°K to 90% excited. A and B are adequately known from infrared and Raman experiments. C can be approximated by a Tarasov-type treatment leading to θ temperatures of 123° and 540° for the three-dimensional and one-dimensional parts, respectively. More detailed spectra are discussed, and a semiempirical best fit is given. The one-dimensional Debye function necessary for this discussion has been computed to five places and is tabulated in steps of hν/kT=0.01.Keywords
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