DYNAMICS OF ADSORPTION OF POLY(ETHYLENE OXIDE) ON A SILICA SURFACE MODIFIED BY GRAFTING

Electron spin resonance spectroscopy of spin-labelled poly(ethylene oxide) terminally anchored on silica and in contact with solutions of poly(ethylene oxide) in different concentrations in benzene has been used to detect indirectly the adsorption process. The nitroxide free radical was 2,2,5,5-tetramethyl-3-pyrroline-1-oxyl-3-carboxylic acid. The ratios of the population of free end segments in solution to that of adsorbed segments on silica as a function of temperature have been evaluated. The conformations of the chains depend upon the concentration of polymer in solution, on their molecular weight and on the grafting ratio already achieved on the surface. The number of molecules that can be accommodated reaches a limiting value. The time involved in the reorganization of the surface layer has been evaluated to amount to several weeks.