Ultra fast processes for solvent evaporation in thin polymer films below Tg

The solvent diffusion coefficient D in a solvent-polymer system can be much larger than the ratio a/ , where a is one monomer length (about 0.5 nm) and is the dominant relaxation time measured e.g. by broadband dielectric spectroscopy [1,2]. The discrepancy can be by up to 6 orders of magnitude and more. We propose here that the solvent diffusion is dominated by path in the liquid with fast relaxation time. It allows to quantitatively explain the discrepancy between D and . Then, we apply this model to describe solvent evaporation of a polymer film with thickness of order a few micrometers. As a consequence of the presence of these fast paths, we show that such a film can dry within an accessible experimental time, even at temperatures well below the glass transition temperature. Our results qualitatively explain corresponding experimental results on PMMA films performed at room temperature [3].