Spectroscopic studies, phonon dispersion and heat capacity of poly (vinylidene chloride)

Poly (vinylidene chloride) (PVDC) is a barrier polymer which has a wide scope in food packaging industries. A comprehensive study of the normal modes and their dispersion in PVDC using Wilson:s GF matrix method as modified by Higgs is reported. It provides a detailed interpretation of IR and Raman spectra. Characteristic feature of dispersion curves, such as regions of high density-of-states, repulsion, and character mixing of dispersion modes, are discussed. Heat capacity has been calculated in the range 50–500 K via density-of-states using Debye relation. It is in fairly good agreement with the experimental data. Heat capacity behavior of PVDC with temperature was observed nearly linear in nature. Heat capacity provides a relationship between microscopic behavior and a macroscopic property. The thermal stability of a polymeric system and its interactive nature with other properties, such as phonon-phonon coupling is also related to thermodynamic behavior. The present study provides a theoretical framework to understand experimental measurements.