Stable Glasses of a Low Fragility Organic Liquid

We have created stable glasses of the low fragility liquid methyl-$\textit{m}$-toluate (MMT, $\textit{m}$ = 60). The MMT stable glass films are prepared by physical vapor deposition and characterized $\textit{in situ}$ with AC nanocalorimetry and dielectric spectroscopy. Stable glasses of MMT have lower heat capacities and increased kinetic stability compared to the liquid-cooled glass. The films transform into the supercooled liquid via two mechanisms. A propagating front controls the transformation of thin films while a bulk mechanism dominates the transformation of thick films. This behavior is similar to other stable glass systems and shows that stable glasses can be prepared from liquids with a very wide range of fragilities (60 $<$ $\textit{m}$ $<$ 147). In one respect MMT stands out from previously studied systems. When a stable glass of MMT is annealed above T$_{g}$ the surface-initiated-front propagates 5 $\mu$m into the sample before the bulk mechanism dominates the transformation. This 5 $\mu$m length scale is significantly larger than what has been observed in other stable glass systems.