Normal mode analyses including phonon dispersion have been performed, to understand completely the spectra (Infrared/Raman) of (gamma NY6), using Wilson GF matrix method and Urey-Bradley force field. Characteristic features of the dispersion curves such as repulsion and region of high density-of-states have been explained. Heat capacity measurements have been interpreted and the limitation of this work discussed. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 3202-3211, 2010