Interfacial dynamics of polymers: Spatial gradient and the collective interface effect

Polymers at interfaces often exhibit striking deviations in dynamics and mechanical behavior compared to their bulk counterparts. These variations can manifest as substantial shifts—sometimes exceeding 50 K—in the glass transition temperature, along with multi-decade changes in elastic modulus, viscosity, and diffusion coefficients. Such pronounced interfacial effects have critical implications for the design and performance of nanostructured materials and are central to the development of multicomponent polymer systems. However, accurately quantifying spatial gradients in interfacial dynamics remains a significant challenge, hindering a clear understanding of the origin of these effects and their connection to the bulk glass transition. In this contribution, we present a new analyses based on dielectric measurements of capped thin film for the spatial gradient of interfacial dynamics with film thicknesses from more than 100 nm down to less than 10 nm. The new analyses enable quantifying the spatial gradient of segmental dynamics and its functional forms. Furthermore, analyses of the thin film less than 10 nm reveal strong collective interface effect, which will also be discussed in the presentation.