Evidence of a Transition Layer between the Free Surface and the Bulk

Wojciech Ogieglo* (Corresponding Author), Kristianne Tempelman, Simone Napolitano, Nieck E. Benes

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

15 Citations (Scopus)
65 Downloads (Pure)


The free surface, a very thin layer at the interface between polymer and air, is considered the main source of the perturbations in the properties of ultrathin polymer films, i.e., nanoconfinement effects. The structural relaxation of such a layer is decoupled from the molecular dynamics of the bulk. The free surface is, in fact, able to stay liquid even below the temperature where the polymer resides in the glassy state. Importantly, this surface layer is expected to have a very sharp interface with the underlying bulk. Here, by analyzing the penetration of n-hexane into polystyrene films, we report on the existence of a transition region, not observed by previous investigations, extending for 12 nm below the free surface. The presence of such a layer permits reconciling the behavior of interfacial layers with current models and has profound implications on the performance of ultrathin membranes. We show that the expected increase in the flux of the permeating species is actually overruled by nanoconfinement.

Original languageEnglish
Pages (from-to)1195-1199
Number of pages5
JournalJournal of physical chemistry letters
Issue number6
Publication statusPublished - 21 Feb 2018


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