KINETICS OF THE GAS-PHASE HALOGENATION OF A POLYETHYLENE SURFACE AS STUDIED WITH X-RAY PHOTOELECTRON-SPECTROSCOPY

X-ray photoelectron spectroscopy (XPS) has been used to determine the kinetics of gasphase halogenation of a polyethylene surface. XPS allows the determination of the concentration of each carbon species present based upon chemical bonding. With this information detailed information about the kinetics has been obtained. The gas-phase chlorination of polyethylene was shown to follow predictable kinetics based on the XPS results. A time distribution of the monochlorinated and dichlorinated species was found, with the monochlorinated species more predominant. Chlorination kinetics are shown to predictably proceed for up to 600-s exposure to chlorine gas. At this exposure a CH2/CHCI/CCI2 ratio of 1/1/0.5 was found. For exposures >600 s, chlorination slows drastically. It is postulated that this latter effect is due to steric effects. Angular-dependent XPS data have shown that chlorination of polyethylene is uniform throughout the sampling depth (~10-70 Å). The XPS results suggest the bromination kinetics are also first order but ~105 slower than that of chlorination. The rate of iodination was found to be orders of magnitude slower than that of bromination. © 1990, American Chemical Society. All rights reserved.