Grafting of high-density poly(ethylene glycol) monolayers on Si(111)

A strategy has been developed for the grafting of poly(ethylene glycol) (PE G) monolayers onto the atomically flat Si(111) surface. This process involv es the direct interaction of the HO-functional group on PEG with a chlorine -terminated silicon surface. The resulting monolayers show exceptional flat ness, with mean roughness on the angstrom scale. Film thickness is determin ed by ellipsometry, X-ray photoelectron spectroscopy, and atomic force micr oscopy. Results for different molecular weights reveal that the grafted PEG molecules are in a brushlike configuration at low molecular weight (MW = 2 00, 300) and a more coil-like configuration at higher molecular weight (MW = 1000, 2000). The surface density of grafted PEG molecules is significantl y higher than those reported in the literature and decreases with increasin g molecular weight, from 92% at MW = 300 to 35% at MW = 2000. Both the brus hlike and the coil-like configurations show excellent properties of protein resistance.