Temperature dependence of the Raman spectra of amorphous glucose in the glassy and supercooled liquid states

The Raman spectra of amorphous glucose between 300 and 4000 cm(-1) over the temperature range 15-55 degreesC are reported. The spectra were recorded at several temperatures both below and above the glass transition temperature, T-g. A two-dimensional covariance spectrum was computed and a least-squares analysis was used to quantify the temperature dependences observed in the spectra, Several vibrational bands were found to be sensitive to the temperature of the material. Some bands also show a changing temperature dependence around the glass transition. A Fermi-type function was found to be suitable as an empirical phenomenological model for the observed changes in the spectra, The wavenumber shifts and intensity changes observed in the spectrum were related to the intramolecular vibrations by a normal coordinate analysis of a single glucose molecule. The spectral changes in the nu (O-H) stretching region suggest a weakening of the hydrogen bond network at the glass transition. Other observed spectral changes suggest a weakening of the van der Waals interactions with increasing temperature, but these changes seem not to be related to the glass transition, Copyright (C) 2000 John Wiley & Sons, Ltd.