Use of spin labels in studying interfacial layers in filled polymer materials

Using nitroxide radicals covalently bonded to the silica surface as spin la bels, data on the mobility of the interfacial layers for some filled polyme rs were obtained. The rotational mobility of spin labels was shown to depen d on the intensity of the molecular motions of adsorbed macromolecules. The glass transition temperature of the polymer matrix was correlated with the ratio of the segmental mobility in the boundary layer to that in the bulk of the polymer. The lower the T-g value for a polymer, the stronger the eff ect of reduction of segmental mobility of adsorbed chains. In polymer matri ces with a high glass transition temperature (PS, PVP), the interfacial lay er and the regions located farther from the surface of filler particles ins ignificantly differ in their molecular mobility.