A study on the vibrational structure of poly(phenylenevinylene)s via low-temperature UV-vis and fluorescence spectroscopy

UV-vis and fluorescence spectroscopy of poly(phenylenevinylene) derivatives were acquired at low temperature (-108 degreesC). Noticeable spectroscopic red-shifts (as large as 17 nm) were detected from both polymers and model compounds in solutions when the temperature was decreased from 25 degreesC to -108 degreesC, indicating that the molecules adopted a more planar conformation at the low temperature. The low temperature spectra revealed the hidden structured absorption and emission. The vibrational structures in the fluorescence spectra were analyzed by using the obtained spectroscopic data at the low temperature. The very similar spectroscopic properties between the polymers (1 and 2) and their model compounds (3 and 4) strongly suggested that the observed spectroscopic red-shift from the polymers at the low temperature was an intrinsic property of the chromophore.