A RAMAN-STUDY OF THE DISORDER-INDUCED BY POLYMER-CHAINS IN MIXED MONOMER-POLYMER CRYSTALS OF THE DIACETYLENE PTS-D

The evolution of the high frequency modes of polymer chains in mixed m onomer-polymer crystals of fully deuterated diacetylene 2,4-hexadiynyl ene bis(p-toluenesulfonate) has been studied as a function of the temp erature by Raman scattering using IR sources. This compound undergoes topochemical complete polymerization in the crystalline state: that gi ves the possibility to control the polymer content x from 0 to 100%. I n both pure monomer and polymer crystals, an antiferroelectric phase t ransition occurs at T-c = 182 K in the polymer and, through an interme diary incommensurate phase, from 155 to 195 K in the pure monomer. The evolution of an elongation mode of the conjugated diacetylene backbon e is reported in mixed monomer-polymer crystals as a function of the t emperature and polymer content from x = 20% to x = 90%. This mode is c oupled to the order parameter. Our results are compared with the previ ous data obtained for the pure polymer. The influence of disorder indu ced by polymer chains in mixed monomer-polymer crystals is discussed i n a qualitative way.