RAMAN SIGNATURE OF THE SIDE-GROUP DYNAMICS IN A MONOMER DIACETYLENE CRYSTAL, PTS-D

Raman scattering is used to make a dynamical study of the disubstitute d and perdeuterated diacetylene pTS-D in monomer crystal from, where a n incommensurate phase exists from T-1 = 155 K to T-1 = 195 K, The low -frequency polarised Raman spectra in the temperature interval 9-300 K show that the phase transition is related to side-group rotations dec oupled as from the diacetylene backbone, as in pTS-D polymer, A compar ison with another disubstituted diacetylene DNP shows that it is very difficult to obtain symmetrical diacetylene polymers in a non-centrosy mmetric structure.