A fourier-transform infrared spectroscopy study of sugar glasses

Fourier-transform infrared spectroscopy (FTIR) was used to study the hydrogen-bonding interactions that take place in vitrified carbohydrates of different chain lengths. The band position of the OH stretching band (vOH) and the shift in band position as a function of temperature were determined from the FTIR spectra as indicators for the length and strength of intermolecular hydrogen bonds, respectively. Differential scanning calorimetry (DSC was used to corroborate the FTIR studies and to measure the change in heat capacity (DeltaC(p)) that is associated with the glass transition. We found that with increasing T-g, the band position of vOH increases, the wavenumber-temperature coefficient of vOH in the glassy state, WTCg, increases, whereas DeltaC(p) decreases. The positive correlation that was found between vOH and the glass transition temperature, T-g, indicates that the length of the hydrogen bonds increases with increasing T-g. The increase in WTCg with increasing T-g, indicates that the average strength of hydrogen bonding decreases with increasing T-g. This implies that oligo- and polysaccharides (high T-g) have a greater degree of freedom to rearrange hydrogen bonds during temperature changes than monosaccbarides (low T-g). Interestingly WTCg and DeltaC(p) showed a negative linear correlation, indicating that the change in heat capacity during the glass transition is associated with the strength of the hydrogen-bonding network in the glassy state. Furthermore, we report that introduction of poly-L-lysine in glassy sugar matrices decreases the average length of hydrogen bonds, irrespective of the size of the carbohydrate. Palmitoyl-oleoyl-phosphatidylcholine (POPC vesicles were found to only interact with small sugars and not with dextran. (C) 2004 Elsevier Ltd. All rights reserved.