Resonance Raman spectra of the polydiacetylene ETCD: Environmental effects on the electronic states of conjugated chains

Abstract

As manifested in solid state electronic spectrocopies, the electronic states of conjugated chain polymers, such as polydiacetylenes (PDA) and polyacetylene, (CH) x, are sensitive to the local crystal packing environment of the conjugated chain. Room-temperature resonance Raman (RR) spectra of single crystals of the PDA from bis -ethylurethane of 5,7-dodecadiyn-1, 12-diol (ETCD), recorded with excitation wavelengths between 488.0 and 632.8 nm, are sensitive to both the excitation wavelength and the presence of unpolymerized monomer. When as-polymerized poly-ETCD crystals are excited in the shorter wavelength (e.g., 488.0 or 514.6 nm) range studied, the observed RR spectra reveal the presence of two PDA electronic states. When residual monomer is extracted from such crystals, the observed RR spectra reveal a marked diminution of the lines of the lower energy spectral state.