Dynamics of the Incommensurate Phase of the Fully Deuterated Diacetylene 2,4-Hexadiynylene Bis( p -Toluene Sulfonate)

Inelastic coherent neutron and Raman scattering is used to make a dynamical study of the disubstituted and fully deuterated diacetylene 2,4-hexadiynylene bis( p -toluenesulfonate) ( p TS-D) in a partially polymerized state ( x = 1.5%). The aim of this study is to investigate the dynamics of the incommensurate phase and to make a comparison with the dynamics of the same monocrystal in the high-temperature phase Even et al. , Phys. Rev ., B52 , 7142.] and the dynamics of the pure monomer p TS-D crystal Bertault et al ., Adv. Mat. for Optics and Electronics , 6 , 317.]. The phason and amplitudon modes are observed as very damped phonon-like excitations. The effect of polymerization on the critical dynamics in p TS-D is discussed.