Probing the Utmost Distance of Polymer Dynamics Suppression by a Substrate by Investigating the Diffusion of Fluorinated Tracer-Labeled Polymer Chains

A facile method was developed to measure the utmost distance of polymer dynamics suppressed by a solid substrate by investigating the diffusion of a fluorinated tracer-labeled polymer in the bottom layer of bilayer samples. Here, a labeled layer of fluorinated tracer-labeled at the polymer chain end of variable thickness was supported on a substrate, and the corresponding homopolymer layer of fixed thickness was deposited on top of the bottom layer. From the critical time ( t *) required for the fluorinated component to diffuse from the bottom layer to the bilayer film surface as a function of the thickness of the bottom layer, a critical thickness of the bottom layer ( h c *), corresponding to the thickness at which t * started to increase, was obtained. This thickness was related to the distance over which polymer dynamics were altered by the substrate. The results showed that h c * was very sensitive to the surface chemistry of the substrate and exhibited both molecular weight and temperature dependencies.