Influence of the Interfacial Effect on Polymer Thin-Film Dynamics Scaled by the Distance of Chain Mobility Suppression by the Substrate

Polymer–substrate interfaces are significant in determining the dynamics of nanoconfined polymers. In this study, an improved understanding of the interfacial effect was gained from the critical distance over which the suppression of interfacial dynamics originating from an interacting substrate propagates. We investigated the effective viscosity of poly(styrene) (PS) thin films with various molecular weights (Mw) on phenyl group-modified substrates and characterized the utmost distance (hc*) of the suppression of chain diffusional dynamics by the substrate. The viscosity of the PS films on the phenyl-modified substrates increased when the film thickness was decreased below a threshold thickness because of the dominant interfacial effect arising from favorable π–π polymer–substrate interactions. The extent of viscosity enhancement is apparently larger for PS with high Mw on the same substrate. Most importantly, we found that the interface-induced viscosity increases for all samples with various Mw values ...