Revealing the structure and dimension of polymer-substrate interfaces is important for the design of polymeric materials applied on a surface. This study demonstrates a molecular ‘nano-ruler’ in a simple and elegant approach for gauging film thickness of an aromatic polymer nano-layer at a polar substrate by playing with a drop of water on the polymer surface. Fascinating alterations in water contact angle with thickness of a polymer nano-layer occur in the ultrathin film regime (0.1 Rg &lt; h &lt; 5 Rg), where Rg is the chain’s radius of gyration dependent on molecular weight. These are associated with changes in the polymer chain conformation at the silicon oxide substrate for the polystyrene thin films, studied by XPS and NEXAFS. The casting solvent and polarity of the substrate can be used to tune the total free surface energy for such ultrathin films. This study is expected to have a broad impact on design of complex interfaces in ultrathin films and coatings.

‘Nano-ruler’ for chain dimension and molecular conformation in ultrathin polymer films based on surface contact angle

255th National Meeting (2018)

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