Thermal expansion of the skeleton of chain molecules in polymer crystals

The expansion of the carbon skeleton of molecules in crystallites and the longitudinal contraction of the crystallite lattice in poly(ethylene) (PE) and poly(caproamide) (PCA) with an increase in the temperature are measured using IR and Raman spectroscopy and x-ray diffraction. The thermal expansion of the carbon skeleton due to transverse vibrations is theoretically calculated within the atomic chain model. The theoretical and experimental data on the thermal expansion of the carbon skeleton are in good agreement.