Resonance Raman Study of the Reversible Thermochromic Phase Transition of a Polydiacetylene.
BROWN UNIV PROVIDENCE R I DEPT OF CHEMISTRY
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Polymers of the type CR-CC-RCn, formed by the solidstate polymerization of the corresponding diacetylene, have extensively delocalized electron density along the chain, as required of a one-dimensional metal. The polymer poly-ETCD, of this form with Ralkylurethane, undergoes a reversible green-red thermochromic phase transition in the 117-137C range. Its Raman spectra reveal dramatic changes in the frequency and intensity of double and triple bond bands as a function of source-frequency and of temperature, as it is raised through the transition. The changes result from the transition and from selective resonance enhancement of vibrations for domains with whose electronic transitions the source is in resonance. The pi-electron delocalization is thus shown by Resonance Raman spectroscopy to occur over segments, or domains, along the polymer backbone.
- Polymer Chemistry
- Atomic and Molecular Physics and Spectroscopy