Surface characterization of polymers for medical devices.

A survey is given on analytical techniques currently applied to the surface characterization of biomedical polymers. The techniques include spectroscopies, thermodynamic and electrochemical measurements and microscopies, respectively. To illustrate the motivation for surface analysis, the hypotheses on the correlations between surface parameters and hemocompatibility of polymers are briefly examined. The applications of the examined methods are illustrated by a number of examples. These examples include the characterization of cellulose membranes (low-flux hemodialysis membranes) by streaming potential measurements and by inverse contact angle measurements. The use of surface spectroscopies (ATR-FTIR and XPS) is demonstrated by considering the optimization of surface modification procedures of vascular prostheses made from poly(tetrafluoroethylene). Furthermore, the characterization of water-swollen cellulose membranes by scanning force microscopy is shown. Finally, the extended application of physico-chemical surface analysis to the investigation of protein adsorption is considered. An example deals with in situ spectroscopic ellipsometry used to study the adsorption of fibrinogen onto a plasma-deposited hydrophobic fluoropolymer and onto poly(ethyleneoxide)-grafted fluoropolymer, respectively.