Is the dynamics of polystyrene films consistent with their glass transition temperature?

摘要

Experiments in the past 1.5 decades have found that the glass transition temperature of polymer films can be noticeably differ-ent from the bulk when the film thickness is decreased below ~100 nm. On the other hand, many dynamic measurements have found results inconsistent with the observed change in the glass transition tempera-ture. One frequently cited reason is that the dynamic properties being probed may not be directly related to the glass transition. Viscosity is a property traditionally used to characterize the dynamic slowing down occurring to a material at the glass transition. In this paper, we report experimental result showing that the viscosity of polystyrene films supported by oxide-coated silicon decreases with decreasing film thickness, consistent with the observed glass transition temperature of the films.