in-situ ellipsometry

Swelling of polymer films

We apply spectroscopic ellipsometry in-situ to analyze swelling of polymer films focusing on the influence of:

external stimulipolymer film composition
  • temperature
  • grafting density
  • salt concentration and pH
  • polymer blend ratio
  • solvent composition
  • gradient film density

With the help of an optical model (Cauchy parameterization or effective medium approach) the following parameters of the swollen thin films are evaluated:

  • in-situ thickness and refractive index
  • in-situ roughness
  • solvent content in vol. %
  • gradient in-situ refractive index if applicable



Biomolecule adsorption

The adsorbed amount of proteins or small drug molecules into swollen polymer films is analyzed by a modified de Feijter approach (1).

Bittrich E. et al. (2018) Polymer Brushes, Hydrogels, Polyelectrolyte Multilayers: Stimuli-Responsivity and Control of Protein Adsorption. In: Hinrichs K., Eichhorn KJ. (eds) Ellipsometry of Functional Organic Surfaces and Films. Springer Series in Surface Sciences, vol 52. Springer, Cham.


In the limit of no protein adsorption (e.g. for antifouling polymer surfaces) we monitor the change in "optical in-situ thickness" d(n-namb) to determine an upper limit of the adsorbed amount of protein.

Bittrich E., Mele F., Janke A., Simon F., Eichhorn K.-J., Voit B., and Appelhans D. Interactions of bioactive molecules with thin dendritic glycopolymer layers Biointerphases 13, 06D405 (2018).