Plasma modification of poly(ester sulfonic) acid aniomoneric membranes

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Title: Plasma modification of poly(ester sulfonic) acid aniomoneric membranes
Author: Slapelis, Linda
Abstract: The effect of variations in plasma parameters on the fluorination, degradation, and etching of poly(ester sulfonic) acid (AQ55) anionomeric membranes was examined. The determination of how the plasma gas composition, power, proximity of the sample to the glow, and time of exposure could be used to maximize surface fluorination and minimize degradation of polymer films is discussed. Membrane surfaces were characterized using contact angles, SEM, gravimetric analysis, DSC, FTIR/MIR, and XPS. These techniques aided in the determination of changes in surface energy, surface topography, sample weight, bulk property, and the identification and quantification of chemical functionalities produced at the AQ55 surface after plasma modification. For all plasma treatments, a range of 9% to 60% atomic fluorine was detected within a depth of 50 A. The degree of fluorination was enhanced by limiting the effects of surface etching and degradation. Three factors which were found to promote surface degradation and etching included; the presence of oxygen, high energy ion bombardment, and elevated plasma temperatures. Under these conditions, the effects of degradation and etching were increased with time of exposure. Gas mixtures of 5% 02/10% Ar/85% CF4 and 10% Ar/90% CF4 were used to ascertain the type and degree of modification produced with and without the presence of oxygen. An increase in the power from 20 W to 50 W increased plasma-surface interactions which resulted in an increase of 10% atomic fluorine at the surface. The effects of ion bombardment were reduced by suspending a quartz plate over the samples during plasma modification. This proved to double the percent atomic fluorine and eliminate degradation and/or etching at the AQ55 surface. The parameters which were found to maximize fluorination and minimize surface degradation and etching include: a 10% Ar/90% CF4 gas composition, 50 W power, long exposure times, and use of the quartz plate shield. Under these conditions, the percent atomic carbon, oxygen and fluorine detected on the surface changed from 74% C, 26% O, 0% F, to 36% C, 4% O, and 60% F.
Record URI: http://hdl.handle.net/1850/11445
Date: 1994-02

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