Jd. Leroux et al., SURFACE FLUORINATION OF POLY(PHENYLENE OXIDE) COMPOSITE MEMBRANES .2.CHARACTERIZATION OF THE FLUORINATED LAYER, Journal of membrane science, 90(1-2), 1994, pp. 37-53
Composite membranes, comprising a selective layer of poly (2,6-dimethy
l-1,4-phenylene oxide) on a microporous ceramic support, were surface
fluorinated under mild conditions. The treatment parameters, fluorine
feed concentration and treatment time, were each varied independently
while the other parameter was kept constant. The fluorinated region wa
s characterized using dynamic contact angle analysis and X-ray photoel
ectron spectroscopy (XPS). The fluorine to carbon ratio increased as a
function of treatment time, but showed little variation when the feed
concentration was varied. A relatively high oxygen to carbon ratio wa
s observed which showed little change over the range of fluorination c
onditions. Angle-dependent XPS showed the concentration of fluorine sp
ecies to be higher at greater depths below the surface. Fluorination t
imes of 5 to 7 min minimized the water contact angle and maximized the
total and polar surface free energies. Water contact angles decreased
after fluorination but showed no definite trend as a function of feed
concentration. The composition of the fluorinated region is discussed
in relation to the gas transport properties of membranes fluorinated
under similar conditions (Part I of this study).