Influence of glycerol on molecular mobility and hydrogen bond network in amorphous glucose matrix.

The effect of glycerol on molecular mobility and hydrogen bonding in amorphous glucose matrix was studied. Phosphorescence from erythrosin B (Ery B) was used to characterize the temperature dependence of mobility in glucose/glycerol films over the temperature range from 100 °C down to -10 °C. Analysis of emission energy and excited state decay kinetics from Ery B provided information about thermally activated modes of matrix dipolar relaxation around and collisions with the excited triplet state of the probe. Both the average rate of matrix mobility and the width of the distribution of matrix mobility rates largely scaled with the effect of glycerol on the glass transition temperature of the glucose/glycerol mixture. The IR hydrogen bond bandwidth increased at higher glycerol content, suggesting that the strength of the bond became more widely distributed with the added glycerol. An increase with temperature in the hydrogen bond peak frequency indicated the transformation of associated hydroxyl to free hydroxyl. These results support a model in which glycerol plasticizes the glucose matrix at mole ratios of 0.1 and above while providing no evidence for the antiplasticization seen in other sugar matrices.