Probing the Dynamics of Molecular Stable Glasses Using Solvent Vapor Annealing with In-situ Ellipsometry

Stable glasses (SGs) are highly dense, low energy glasses that are made by physical vapor deposition (PVD). Because of their desirable properties and potential for wide range of applications, they are extensively studied glasses. However, estimating their dynamics can be difficult since they are produced directly into the SG state during PVD. We introduce a novel and indirect method of measuring the dynamics of SGs using solvent vapor annealing (SVA), combined with in-situ ellipsometry. Using this technique, we have shown that the mechanism by which solvent penetrates a molecular glass film, depends on the solvent vapor pressure. Above a certain threshold of the solvent vapor pressure, the swelling front moves linearly into the film in a Case II diffusion process. By monitoring the front’s motion across the film, we can compare the dynamics of SG films of various stability produced at different deposition temperatures. The results correlate well with thermal transformation growth fronts but in this case, can be used to characterize glasses with a wider range of stability and with more accuracy. The SVA process is also able to provide more details of the interface dynamics and their differences compared to the bulk glass.