Plasma modification of PTFE surfaces Part I: Surfaces immediately following plasma treatment

Polytetrafluoroethylene (PTFE) was treated in a low-power plasma using a series of feed gases (O-2, Ar, N-2 and NH3) and the resulting surface modifications were evaluated by x-ray photoelectron spectroscopy, static secondary ion mass spectroscopy, dynamic contact angle measurements and atomic force microscopy. All plasma treatments caused light etching, but the nature and extent of chemical modification varied considerably. Fluorine depletion of the surface was affected most efficiently by Ar and least effectively by O-2 plasma. New functionalities were introduced to the surface either from plasma derivatives of the feed gases or by post-treatment exposure to moist air; Ar, N-2 and NH3 were more effective than O-2 in this respect. The wettability of virgin and plasma-treated materials in phosphate-buffered saline solution (PBS) and 1-bromonaphthalene was studied, and the observations are discussed in a framework that correlates contact-angle hysteresis with surface chemistry in a semi-quantitative manner. In Part II of this work, further changes of the surface chemistry and wettability of virgin and plasma-treated materials arising due to storage in PBS or air are described. Copyright (C) 2001 John Wiley & Sons, Ltd.