Spectroscopic study of soluble poly(2,5-dialkoxy-1,4-phenylene-alt-oligoethynylene)s

The Raman and UV-Vis spectra of poly(2,5-dialkoxy-1,4-phenylene-alt-oligoet hynylene)s bearing ethynylene, 1,3-butadiynylene, or 1,3,5,7-octatetraynyle ne segment and corresponding oligoethynylene models, diphenylacetylene, dip henylbutadiyne, and diphenyloctatetrayne, have been studied. The Raman freq uencies (nu) around 2100-2200 cm(-1) due to symmetric C=C stretching mode i n the oligoethynylene segments of the models as well as the polymers shifte d to lower wavenumbers with increasing number of ethynylene units. The nu v alues were correlated with an inverse of the carbon numbers (N) in the olig oethynylene segment. The absorption maxima (lambda(max)) of the polymers in the longest UV-Vis absorption were all shifted to longer wavelengths than the corresponding models. The UV-Vis absorption bands of the polymers were also correlated with a relationship, lambda(2) vs, number of carbon-carbon triple bonds in the oligoethynylene segment as has been well established fo r various polyenes and oligoynes. (C) 2000 Elsevier Science B.V. All rights reserved.