PHONONS IN 7(2) HELICAL POLY(4-METHYL-1-PENTENE)

The normal modes and their dispersions for isotactic poly(4-methyl-1-p entene) have been obtained in the reduced zone scheme using Wilson's G F matrix method as modified by Higgs. The zone centre frequencies and Urey-Bradley potential field have been obtained by fitting the observe d Fourier transform infra-red absorption bands. Some of the characteri stic features of the dispersion curves are repulsion, exchange of char acter and Von Hove type singularities. The heat capacity obtained from the density-of-states agrees with the experimental data up to 305 K, at which glass transition sets in and the experimental curve exhibits a marked change in slope.