APPLICATIONS OF RAMAN-SPECTROSCOPY TO THE STUDY OF POLYDIACETYLENES AND RELATED MATERIALS

Raman spectroscopy is a useful and sensitive probe of the structure and properties of polydiacetylene (PDA) materials. Using 1064, 632.8, 514.5, 488.0, and 457.9 nm as wavelengths of excitation, Raman spectra were observed using light polarized in the direction of the chain axis for the PDA from 1,6-di-N-carbazolyl-2,4-hexadiyne (DCH) and 1,1,6,6-tetraphenylhexadiynediamine (THD) and for chemically modified versions of these materials. From the changes in the spectra with wavelength of excitation, it was deduced that these pristine PDA single crystals have disordered surface phases. For poly-DCH that has gained six Br atoms per repeat unit, Raman spectra provide a direct indication of the extensive conversion of the PDA backbone structure to that of a mixed polyacetylene. The normal modes associated with triple- and double-bond stretching on the PDA backbone provide a useful structure-property relationship for the characterization of the products of diacetylene polymerizations where the degree of definition does not approach that of fully polymerized single crystals.