Connecting the density distribution and segmental dynamics of confined polymer films

Polymers show a lot of anomalous behavior when they are confined by the thickness. In this work, we focus on the relation between the density and the segmental dynamics for confined polymer films of poly-(4-chlorostyrene) -P4ClS- and Poly(2-Vinylpyridine) -P2VP-. When confined by its thickness, the dynamics of P4ClS films is found to increase until it reaches the thickness of around 10 nm. Then, at 10 nm, it shows again the bulk-like behavior, which is attributed to the dominating substrate interaction that hinders the faster dynamics induced by the free surface. Whereas, the P2VP film showed bulk like dynamics at a thickness of 24 nm. The polymer density distribution followed by using Time-of-Flight Secondary Ion Mass Spectrometry (ToF SIMS) depth profiling suggests that there can be diverse underlying mechanisms for obtaining faster dynamics in films at a thickness between 110 and 10 nm. •There can be diverse underlying mechanisms for the segmental dynamics observed in confined polymer films.•The average density of the entire film and the density distribution inside the thin film are distinct.•ToF SIMS depth profiling can directly probe the density distribution in confined polymer films.•Interfacial interactions can control the density distribution in polymer thin films.