Studying the influence of chemical structure on the surface properties of polymer films

The influence of the chemical structure of polymer surfaces with systematically altered chemical composition (aliphatic, aromatic, ester group in the side chain/main chain, ether- and sulfone groups), among them new polymeric structure synthesized in our group, on the surface properties was examined using carefully synthesized and purified polymers. The aim of the research was to elaborate direct structure–property relationships between the chemical structure and parameters describing the surface properties, such as wetting, surface free energy and adsorption of proteins. Thin films were prepared by spin coating and characterized with a combination of complementary methods (optical microscopy, AFM, contact angle measurements, streaming potential measurements, XPS, ellipsometry). Finding correlations required pure and well-characterized polymers as well as the formation of smooth, thin films with low surface roughness. The chemical structure of the polymers used gave rise to a broad range of surface free energies varying from 9.8 to 40.0 mN/m. The adsorption of human serum albumin as model protein on these films was determined by using a static method, the high performance liquid chromatography technique (HPLC). In tendency a correlation between chemical structure (represented by the ratio between oxygen and carbon), surface free energy and amount of adsorbed HSA could be derived.