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Authors Grundke, K. ; Pospiech, D. ; Kollig, W. ; Simon, ; Janke, A.
Title Wetting of heterogeneous surfaces of block copolymers containing fluorinated segments
Date 07.08.2001
Number 9263
Abstract The wetting of well-characterized heterogeneous surfaces of block copolymers has been studied by low-rate dynamic contact angle measurements using axisymmetric drop-shape analysis. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to investigate the roughness, the heterogeneity and the chemical composition of the surfaces. By changing the block length of polysulfone and semifluorinated polyester segments in the block copolymers, the surface heterogeneity of thin films prepared on silicon wafers could be controlled. Tapping-mode AFM measurements showed that soft, hydrophobic domains of varying size on the submicrometer length scale were obtained on these surfaces (60-250 nm). The mean roughness was of the order of several nanometers. The results of the contact angle measurements showed that neither roughness nor heterogeneity had a significant effect on the advancing contact angle of water, at the scale of the features present; however, the contact angle hysteresis increased with increasing percentage of the soft domains. We assume that liquid retention by the solid upon retraction of the three-phase line is the main cause for the observed increase in contact angle hysteresis. Concerning the molecular composition of these block copolymer surfaces, angle-resolved XPS analysis showed a surface segregation of fluorine within the surface region. A direct correlation was found between the fluorine content of the block copolymer surfaces and the advancing contact angle of water.
Publisher Colloid and Polymer Science
Wikidata 19
Citation Colloid and Polymer Science 279 (2001) 727-735
DOI https://doi.org/10.1007/s003960100487
Tags wetting axisymmetric drop shape analysis contact angle hysteresis heterogeneous surfaces block copolymers contact-angle interpretation drop shape-analysis force microscopy energy hysteresis tensions films wettability monolayers

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