The uses of polymer-based hybrid materials such as nanocomposites will increase in the future due to the demand of the society to safe energy as well as other resources. Interfaces on a spatial scale of few nm are crucial for the performance of this class of materials. In hybrid materials these internal interfaces on the nanoscale are difficult to access. Therefore, here thin films will be considered as model systems for internal interfaces.<br/>Films of PVME and P2VP with thicknesses from below 10 nm to 200 nm are prepared and investigated by spectroscopic ellipsometry, atomic force microscopy and dielectric spectroscopy. Attention is paid to irreversible adsorbed layer on the substrate. Firstly, the growth kinetics of the adsorbed layer was studied combining a leaching technique and AFM. A critical initial film thickness for the formation of a surface-filling adsorbed layer is found. Ellipsometry measurements were carried out to investigate the influence of the adsorbed layer on the glass transition temperature of the films. For 30 nm films and below, the influence of the adsorbed layer percolates strongly to the bulk-like layer of the film. The molecular dynamics of the adsorbed layer was studied by dielectric spectroscopy. One process was revealed, which was assigned either to molecular fluctuations taking place in a loosely-bounded the part of the adsorbed layer, or to the desorption/adsorption of segments at the substrate.

Characterization of nanometric thin films as model systems for interfaces

ACS Spring 2022

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