STRUCTURE AND MOLECULAR-MOTION OF POLY(ETHYLENEOXIDE) CHAINS ADSORBEDON A SILICA-TETHERED POLY(METHYLMETHACRYLATE) BY THE SPIN-LABEL METHOD

The spin-label method was used to study the structure and molecular mo tion of poly(ethylene oxide) (PEO) chains adsorbed on a silica-tethere d poly(methyl methacrylate) (PMMA). Spin-labelled PEO with a narrow mo lecular weight distribution, having number averaged molecular weight ( M-N) = 6.0 x 10(3), was adsorbed on the surface of the silica-tethered PMMA with various grafting ratios in carbon tetrachloride solution at 35 degrees C. ESR spectra were measured at various temperatures after the samples were completely dried. The ESR spectra are composed of tw o spectra arising from spin-labels attached to ''train'' and ''tail'' segments, which are strongly and weakly interacted with the silica sur face, respectively. The fractional amount of the ''tail'' segments inc reases extremely with the grafting ratio of PMMA, Molecular mobility o f the PEO chains estimated from the temperature dependence of the ESR spectra also decreases significantly with the grafting ratio of PMMA. Structure and molecular motion of the PMMA chains tethered on the sili ca were also studied using the spin-labelled PMMA. Consequently, parts of the PEO segments penetrate into the PMMA chains and is adsorbed on the silica surface (''train'' segments), whereas parts of the PMMA se gments protrude from the surface. The other PEO segments are entangled with the tethered PMMA chains (''tail'' segments).