THICKNESS OF A SILICA-TETHERED POLY(ETHYLENE OXIDE) LAYER MEASURED BYSPIN-LABELING

EPR spectroscopy of labeled poly(ethylene oxide) (PEO) grafted on sili ca has been used to characterize the conformation and local dynamics o f the chains. Grafted molecules of MW 2000 with grafting ratios of 0.0 45, 0.057, 0.126, and 0.42 molecules/nm(2) were in contact with benzen e. The mobility of the label was compared with that observed for solut ion of PEO from very diluted to highly concentrated and even bulk PEG. Thus, the concentration inside the grafted layer could be evaluated a nd also the thickness, which evolves rather linearly with the grafting ratio. (C) 1995 John Wiley & Sons, Inc.