Characterization of Thin Polymer Films on Solid Substrates by Temperature Dependent Spectroscopic Vis-Ellipsometry (T-Ellipsometry)

摘要

The knowledge of the effects of surface and interface on the dynamic properties of polymers in thin layers is an important scientific and technology issue e.g. to control and understand processes, such as welding, adhesion, coating and melt-pressing. Experimental techniques like dielectric spectroscopy, AC-calorimetry and dilatometry have been developed to characterize molecular dynamics of polymers under confinement in thin films. Recently, we published first results on thin hyperbranched aromatic polyester films.In our actual experiments we use the T-ellipsometry to determine thermal properties (e.g glass transition Tg, coefficient of thermal expansion CTE and mass loss) of thin polymer films under defined atmosphere (e.g. inert gas). Mostly in ellipsometric analysis the thermal expansion of the silicon substrate as well as possible oxidation reactions during heating are neglected. But, from our point of view, this has to be absolutely considered. Therefore, here we report temperature dependent ellipsometry results on the well-known linear polymer PMMA (poly (methylmethacrylate)) as well as on hyperbranched polyesters with graded functionality and different molar masses on silicon. We show thermal properties as well as confinement effects in thin films and compare them with the bulk properties.