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

Abstract

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 (M w) on phenyl group-modified substrates and characterized the utmost distance (h c *) 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 M w on the same substrate. Most importantly, we found that the interface-induced viscosity increases for all samples with various M w values and substrates can be linearly correlated with the distance over which the suppression of interfacial dynamics extends, which makes it possible to qualitatively evaluate the effectiveness of the interfacial effect.

The role of the molecular weight of the adsorbed layer on a substrate in the suppressed dynamics of supported thin polystyrene films

“…In our previous work, was adjusted by changing the loop size of the adsorbed chain on the substrate 20 and the phenyl group content on a phenyl group-modified substrate. 2 The interface-induced PS viscosity and T g increased linearly with the distance of chain mobility suppressed by the substrate. 2,7 Zuo 7 and Bram 45 found that strong interpenetrations between the adsorbed layer and the free chains in the film impacted thin film dynamics.…”

“…2 The interface-induced PS viscosity and T g increased linearly with the distance of chain mobility suppressed by the substrate. 2,7 Zuo 7 and Bram 45 found that strong interpenetrations between the adsorbed layer and the free chains in the film impacted thin film dynamics. It is reasonable to suggest that the adsorbed layer entangles with free chains, affecting and suppressing the dynamics of the supported film.…”

“…It is widely accepted that the interfacial effect plays a crucial role in the resulting physical properties of supported ultrathin polymer films and nanocomposites, with large differences in the physical performance observed when different substrates are used. 1–4 For example, an ultrathin poly(methyl methacrylate) film showed a decrease in the glass transition temperature ( T g ) compared with the bulk T g when supported by gold substrates, while an increase in T g resulted when supported by silicon substrates. 1 The T g of ultrathin PS films could be adjusted by modifying the various aromatic groups anchored onto silicon substrate surfaces 3,5 and the loop size of the adsorbed polystyrene (PS) chains.…”

Molecular Orientations at Buried Conducting Polymer/Graphene Interfaces

“…In this research, we applied sum frequency generation (SFG) vibrational spectroscopy to study the molecular structure at the buried graphene/PT interfaces. SFG is a coherent, second-order nonlinear optical spectroscopy that utilizes the chemical selectivity of IR and Raman spectroscopies to detect molecular structures including functional group orientation at a medium where the inversion symmetry is broken. − In a typical SFG experiment, a visible laser beam with a fixed frequency and a frequency-tunable IR beam overlap both spatially and temporally at the sample interface where two photons are combined; a third photon with the sum of the two input photons’ energies is generated. According to the selection rules of SFG spectroscopy, only a medium with no inversion symmetry can generate an SFG signal under the electric-dipole approximation. ,,,,, In the bulk environment, most of the polymer molecules are randomly distributed and thus form an isotropic sample that possesses inversion symmetry, which will not generate an SFG signal.…”

Decoupling Role of Film Thickness and Interfacial Effect on Polymer Thin Film Dynamics

“…Thin polymer films have been used in a wide variety of applications, such as nanoprinting, electronics, and sensors. Experiments and simulations show that molecular dynamics and associated physical properties, such as the glass transition temperature ( T g ), − physical aging, , diffusion, viscosity, , and crystallization, , all deviate from the corresponding bulk properties …”