Induced glassy behavior in the melt of glycerol and aerosil dispersions

Abstract

A high-resolution calorimetric spectroscopy study has been performed on pure glycerol and colloidal dispersions of an aerosil in glycerol covering a wide range of temperatures from 300 K to 380 K, deep in the liquid phase of glycerol. The colloidal glycerol+aerosil samples with 0.05, 0.10, and 0.20 mass fraction of aerosil reveal glassy, activated dynamics at temperatures well above the $T_g$ of the pure glycerol. The onset of glass-like behavior appears to be due to the structural frustration imposed by the silica gel on the glycerol liquid. The aerosil gel increases the net viscosity of the mixture, placing the sample effectively at a lower temperature thus inducing a glassy state. Given the onset of this behavior at relatively low aerosil density (large mean-void length compared to the size of a glycerol molecule), this induced glassy behavior is likely due to a collective mode of glycerol molecules. The study of frustrated glass-forming systems may be a unique avenue for illuminating the physics of glasses.