Characterization of polymer surfaces using captive bubble ADSA contact angle measurements - effect of adsorbed substances (proteins, ions)
The hydrophobicity/hydrophilicity of a solid surface is usually expressed in terms of wettability which can be quantified by contact angle measurements. In order to study highly hydrated polymer layers, captive bubble contact angle techniques have been used. As in the case of sessile liquid droplets, the contact angle of the captive bubble is normally measured by the conventional goniometer technique. We use a captive bubble arrangement in conjunction with axisymmetric drop shape analysis-profile (ADSA-P) to quantify the wettability of different polymer materials (e. g. hydrophilic cellulosic materials or hydrophobic fluoropolymers) in contact with pure water, electrolyte or aqueous protein solutions.
- Fig. 2a A schematic of the experimental set-up for ADSA-P captive bubble contact angle measurements.
- Fig. 2a Inverse low-rate dynamic contact angles on a fluorohydrocarbon polymer surface (A) in contact with a phosphate buffered saline (pH=7.4) measured by ADSA-P captive air bubble technique
- Fig. 2b Inverse low-rate dynamic contact angles onadsorbed fibrinogen layer (B) in contact with a phosphate buffered saline (pH=7.4) measured by ADSA-P captive air bubble technique
Using this experimental technique to measure inverse low-rate dynamic contact angles, the wettability of adsorbed protein layers in their highly hydrated state can be studied. After the protein adsorption (human serum albumin, fibrinogen) the physicochemical state of the solid-liquid interface is changed from a hydrophobic to a hydrophilic state observed by the decrease of the inverse advancing and receding contact angles. Differences in the overall hydrophobicity/hydrophilicity of the adsorbed protein layers could be revealed depending on the type of protein and on the concentration of the protein solution. In addition, we apply ADSA-P captive bubble contact angle measurements to study the effect of ions on the solid-water interfacial energy using hydrophobic and hydrophilic polymer surfaces in contact with aqueous electrolyte solutions. In the centre of our interest are the relations between electrochemical properties, adsorption and wettability of polymer surfaces and the theory of thin liquid films by Frumkin, Derjaguin and Churaev.
Fields of Research
- Characterization of wetting and adhesion properties of biocompatible polymers including adsorbed proteins
- Relation of wettability, adsorption and electrochemical properties of polymers
Coworkers
- Dr. Karina Grundke
- Dipl.- Chem.Ing. Nicole Petong
